Doctors perform eye surgery on a patient at the clinic


View from Adelaide Road


AIOS Headquarter


Pranab Mukherjee delivering the inaugural address at the 28th Congress of ASIA Pacific, Academy of Ophthalmology in Conjunction with the 71st Annual Conference of All India Ophthalmological Society (APAO-AIOS-2013)


EBO


LVPEI Bhubaneswar


LVPEI NATCO Kothur


A doctor examining patients on the morning following surgery


NEI Director Michael F. Chiang


Orbis McDonnell Douglas DC-8-21 at Birmingham Airport, England


Orbis International McDonnell Douglas DC-10-10 at Hong Kong.


Orbis International McDonnell Douglas MD-10-30 at Malta International Airport, Malta


Examination and laser treatment suite inside the Flying Eye Hospital


RPI's official logo


SEE Patient in Phnom Penh, Cambodia. January 2019.


Moorfields Eye Hospital


The main portico of  University College London


Figure 1.0 - Basic anatomical features of the human eye


Figure 2.0 - Contact lens


Figure 3.0 - Molecular imprinting technique


Figure 4.0 - Example of a nanoparticle


Figure 5.0 - Example of zero-order release kinetics (y = % of drug released from contact lens; x = time (days))


Figure 6.0 - Cornea epithelium


Figure 7.0 - Glaucoma complications


Figure 8.0 - Dry eye syndrome complications


Eye drops being applied


These eye drops are packaged for single use, without preservatives


Man applying eye drops


Intravitreal administration delivers substances directly into the vitreous chamber.


Schematic diagram of the human eye showing.


Sagittal section of the human eye showing the Tenon's capsule, labelled  Fascia bulbi


Schematic diagram of the human eye showing sclera and choroid. The suprachoroidal space is located between these two layers.


Schematic diagram of the human eye.


Anomaloscope using a Rayleigh Match


A  United States Navy  optometrist technician using an autorefractor during a humanitarian assistance project in  Nicaragua  in 2008


Shin Nippon Nvision K-5001 Refkeratometer


The optics inside a Shin Nippon Nvision K-5001 Refkeratometer


An Exophthalmometer


An example of the  Landolt C  eye chart (also known as the Japanese eye chart.)


Frenzel goggles


A fundus camera


A close-up of the controls of a Topcon retinal camera


Fundus photography is also used to document the characteristics of diabetic retinopathy such as macular edema and microaneurysms. This is because retinal details may be easier to visualize in fundus photographs as opposed to with direct examination.


Goldmann Applanation Tonometer attached with Slit lamp biomicroscope


Sample view of anterior synechiae


Sample view of anterior synechiae with indentation gonioscopy


Jackson cross cylinder of +/- 0.25 diopter


An eye doctor examining a patient with a keratometer


Typical presentations of keratoconus as detected through a keratometer


Lens clock


Use and measurements using a calibrated lens clock


A Lensmeter in an Optical shop


A simple lensmeter cross sectional view.   1  – Adjustable eyepiece  2  – Reticle  3  – Objective lens  4  – Keplerian telescope   5  – Lens holder   6  – Unknown lens  7  –  Standard lens   8  –  Illuminated target   9  – Light source  10  – Collimator   11  – Angle adjustment lever  12  – Power drum (+20 and -20 Diopters)  13  – Prism scale knob


The slit lamp of a Goldmann tonometer


Semicircles seen during Goldmann tonometry through slit lamp


The PASCAL dynamic contour tonometer


Schiøtz tonometer


Diaton transpalpebral tonometer


oDocs Fundus, a smartphone retinal imaging adapter


Ophthalmoscope (left) and  otoscope  combination by Welch Allyn


A phoropter can measure refractive error to determine an individual's spectacle lens prescription during an eye examination.


Side of a phoropter that faces the patient


The American Optical Ultramatic RxMaster of 1967


Very early phoropters. Top, the 1917 Woolf Ski-Optometer of New York City, with cylinder.; bottom, the 1915 DeZeng Phoro-Optometer model 570, Camden, NJ. The mounting arms on both devices attached at the bottom.


The early DeZeng/AO lineage. Top row: Model No. 570, 1917 or earlier, No. 584, 1922. Bottom row: No. 589, 1934, No. 590, 1948.


What was available in 1934. Top left, the Genothalmic Refractor; top right, the AO 589 Phoroptor; bottom, the B&L Greens' Refractor, still much in use today.


Neurological assessment with NeuroLight pupillometer (IDMED, IDMED Corp.)


NPi-300 automated infrared pupillometer (NeurOptics, Inc.)


NeurOptics, Inc. Pupillometer Results Screens


Eye examination  with the aid of a slit lamp.


Side view of a slit lamp machine.


Cataract  in human eye: magnified view seen on examination with the slit lamp


Diffuse Illumination of anterior segment


Lesions are seen in superficial layers of cornea by direct focal illumination


Retro-illumination of anterior subcapsular cataract


Indirect lateral illumination of corneal ulcer


Sclerotic scatter illumination showing KP on cornea


Fundoscopy by using +90 diopter lens with the slit lamp


Zeiss Type slit lamp


Haag Streit Type slit lamp


An undine with its original box


Eyelid and prominent eyelashes of a human adult


Plan of retinal neurons.


1:posterior segment 2:ora serrata 3:ciliary muscle 4:ciliary zonules 5:Schlemm's canal 6:pupil 7:anterior chamber 8:cornea 9:iris 10:lens cortex 11:lens nucleus 12:ciliary process 13:conjunctiva 14:inferior oblique muscule 15:inferior rectus muscule 16:medial rectus muscle 17:retinal arteries and veins 18:optic disc 19:dura mater 20:central retinal artery 21:central retinal vein 22:optic nerve 23:vorticose vein 24:bulbar sheath 25:macula 26:fovea  27:sclera 28:choroid 29:superior rectus muscle 30:retina


Figure 1. Calculating EZ ratio.


Figure 2. Different anterior chamber depths as seen from the lateral perpendicular (profile) view. The more forward the pupil is, the shallower the anterior chamber. In the leftmost photo, the pupil is relatively posterior (set back), indicating an EZ ratio of < 0.5 and an anterior chamber deeper than 2.5 mm. In the middle photo, the pupil is midway between the sclera posteriorly and the cornea anteriorly, indicating an EZ ratio of 0.5, and a medium chamber depth of about 2.5 mm. In the rightmost photo, the pupil is very anterior (forward), indicating an EZ ratio of more than 0.5 and a shallow anterior chamber of less than 2.5 mm.


Diagram of  anterior segment  of a  human eye  ( horizontal section  of the right eye)  1.  Lens , 2.  Zonule of Zinn or ciliary zonule , 3.  Posterior chamber  and 4.  Anterior chamber  with 5.  Aqueous humour  flow; 6.  Pupil , 7.  Corneosclera  with 8.  Cornea , 9.  Trabecular meshwork  and  Schlemm's canal . 10.  Corneal limbus  and 11.  Sclera ; 12.  Conjunctiva , 13.  Uvea  with 14.  Iris , 15.  Ciliary body .


Bergmeister's papilla, histological section.


Cutting lateral canthus


Sheep eye lens capsule with ligaments attached. The capsule is lifting off the lens showing cell fiber ends beneath.


Microscope image of lens capsule in relation to lens cell types


Micrographs and 3D drawing of a "foot" structures on eye lens capsules


A thin section showing two feet penetrating into the lens capsule. The capsule appears just under 10 microns thick in this micrograph though the apparent thickness will vary with the angle of section cut so the actual thickness may be less. Large numbers of small vesicles can also be seen


One of the feet and higher magnification. Thin pale fibres can just be seen within the cytoplasm


Structure on the outside surface of eye lens capsule at equator showing the fused cells and vesicles associated with it


A sheep lens with the capsule stripped off. The classic lens shape is practically lost without the support of the capsule.


Lens embryogenisis


Choroidal blood flow revealed with ICG-angiography (Spectralis, Heidelberg) and  laser Doppler imaging [ 6 ]


Ciliary  ganglion  with parasympathetic fibers of ciliary nerves.


Cone cell structure


Bird ,  reptilian , and  monotreme  cone cells


Image of a human eye showing the blood vessels of the bulbar conjunctiva


Hyperaemia  of the superficial bulbar conjunctiva blood vessels


Vertical section of human cornea from near the margin. (Waldeyer.) Magnified. 1:  Epithelium . 2:  Anterior elastic lamina . 3:  substantia propria . 4:  Posterior elastic lamina  (Descemet's membrane). 5:  Endothelium  of the  anterior chamber . a: Oblique fibers in the anterior layer of the  substantia propria . b: Lamellae, the fibers of which are cut across, producing a dotted appearance. c: Corneal corpuscles appearing  fusiform  in section.  d: Lamellae, the fibers of which are cut longitudinally. e: Transition to the  sclera , with more distinct fibrillation, and surmounted by a thicker  epithelium . f: Small blood vessels cut across near the margin of the cornea.


Corneal cross-section imaged by an  SD-OCT


In a healthy eye, the cornea presents as a clear, domed, glossy covering over the  iris  and  pupil .


The cornea becomes opaque after death (provenance: genus  Bos )


Slit lamp  image of the cornea, iris and lens (showing mild  cataract )


Hexagonal cells of corneal endothelium visualized by  specular microscopy .


The corneal limbus manifests as a  dark ring around the iris . Its prominence varies by individual


An alignment of the human crystallin proteins alpha, beta, and gamma from Uniprot.


Copper disposition on corneal Descemet's membrane


This image highlights the epicanthic folds in a person of  Mongol  descent.


Swedish ski racer  Jens Byggmark  with an epicanthic fold over his left eye.


The  Khoisan  and some other African groups have a high frequency of the epicanthic fold.


Lateral and anterior views of the extraocular muscles also showing  common tendinous ring  origin and  trochlea


Extraocular muscles  are shown in this image of the left eye (lateral view). Click on the structures for more information.


The vestibulo-ocular reflex. A rotation of the head is detected, which triggers an inhibitory signal to the extraocular muscles on one side and an excitatory signal to the muscles on the other side. The result is a compensatory movement of the eyes.


The oculomotor (III), troclear (IV) and abducens (VI) nerves supply the muscle of the eye. Damage will affect the movement of the eye in various ways, shown here.


Blood vessels of the eyelids, front view


Eyelashes grow from the eyelid margin and project outwards and curl away from the eye, to protect the eye from foreign objects


Eyelid affected by  stye


A South Korean woman, before (left) and after (right) undergoing  double eyelid surgery . Note the presence of the  epicanthic fold  in both photographs.


Eyelid skin pushing the central and inner upper  eyelashes  downwards into this person's field of vision, exacerbated by the excess length and thickness of their eyelashes. Note that the lashes in the outer portion of the eyelid are not pushed by the eyelid and curl upwards.


Time-domain OCT of the macular area of a retina at 800 nm, axial resolution 3 μm


Spectral-domain OCT macula cross-section scan


Macula histology (OCT)


Diagram showing the relative acuity of the left human eye (horizontal section) in degrees from the fovea


Photograph of the retina of the human eye, with overlay diagrams showing the positions and sizes of the macula, fovea, and optic disc


Illustration of the distribution of cone cells in the fovea of an individual with normal color vision (left), and a color blind (protanopic) retina. Note that the center of the fovea holds very few blue-sensitive cones.


Distribution of rods and cones along a line passing through the fovea and the  blind spot  of a human eye [ 22 ]


A  fundus photo , showing the  optic disc  as a bright area on the right where blood vessels converge. The spot to the left of the centre is the  macula . The grey, more diffuse spot in the centre is a shadow  artifact .


Schematic diagram of the human eye


A montage of five pictures of the right eye of a male subject with partial heterochromia, demonstrating torsional eye movement


Depicts nerve branches that are involved in the autonomic innervation of the lacrimal gland. The terminal parts of the pathway are variable between individuals and differ for the other glands of the deep face.


3D lens model from sheep with parts labeled and images of cells from different parts overlayed


Sheep eye lens para-formaldehyde fixed front view. Small lenses are about 1cm in diameter. Small bumps at edge are remnants of suspensory ligaments


Sheep lens fixed side view. Note the largest lens has damaged capsule and iris attached


Microscope image of lens cell types and capsule


Sheep lens capsule removed. Decapsulation leads to a nearly formless blob.


Eye lens micrographs and diagram of growth region of the capsule.


Cellular and supercellular structure in the mouse lens. Photos at increasing depth: A-Epithelium B-Broadening fiber ends C-Fiber ends lock together D-F- Voids G-Vacuoles I-Sutures


Left to right we have a smooth capsule, a small patch of epithelium next to fused lens fibers or perhaps a void, straighter fibers, and finally wrinkled fibers


Similar to a human, this is a lens forming in a chicken eye


Pattern of lens fibers (anterior and lateral aspect)


Bony fish eye. Note the spherical lens and muscle to pull the lens backward


An image that is partially in focus, but mostly out of focus in varying degrees.


Eye and detailed ray path including one intraocular lens layer


Two horse lenses suspended on water by cling wrap with 4 approximately parallel lasers directed through them. The 1 cm spaced grid indicates an accommodated, i.e. relaxed, near focus, focal length of around 6cm


Schachar model of lens focus


Tracing of Scheimpflug photographs of 20 year old human lens being thicker focusing near and thinner when focusing far. Internal layering of the lens is also significant


Wrinkled lens fibers in picture below compared to straight fibers above


Diving bird (Cormorant) lens focusing can be up to 80 dioptres for clearer underwater vision.


Graph showing  optical density  (OD) of the human crystalline lens for newborn, 30-year-old, and 65-year-old from wavelengths 300-1400 nm.


Channels regulate lens transport.


Photograph of the retina of the human eye, with overlay diagrams showing the positions and sizes of the macula, fovea, and optic disc


Schematic diagram of the macula lutea of the retina, showing perifovea, parafovea, fovea, and clinical macula


First drawing of the meibomian gland by   Heinrich Meibom . Year 1666.


Meibomian glands in the lower eyelid imaged under amber light to show vasculature support and the gland structure.


Bird cone cell, including oil droplet.


Schematic diagram of the  human eye , with the optic disc, or blind spot, at the lower left. Shown is a horizontal cross section of the right eye, viewed from above.


Optic disc cross-sections imaged by an SD-OCT.


3D model of orbit with surrounding bones


The seven bones that form the orbit: yellow =  Frontal bone green =  Lacrimal bone brown =  Ethmoid bone blue =  Zygomatic bone purple =  Maxillary bone aqua =  Palatine bone red =  Sphenoid bone teal =  Nasal bone  (illustrated but not part of the orbit)


Tear system : a. tear gland / lacrimal gland, b. superior lacrimal punctum, c. superior lacrimal canal, d. tear sac / lacrimal sac, e. inferior lacrimal punctum, f. inferior lacrimal canal, g. nasolacrimal canal


Eye bags  – minor periorbital puffiness usually detectable below the eyes only.


Periorbital  edema .


Normalized human photoreceptor absorbances for different wavelengths of light [ 3 ]


Illustration of the distribution of cone cells in the fovea of an individual with normal color vision (left), and a color blind (protanopic) retina. Note that the center of the fovea holds very few blue-sensitive cones.


Distribution of rods and cones along a line passing through the fovea and the blind spot of a human eye [ 7 ]


The absorption of light leads to an isomeric change in the retinal molecule.


Overview of the retina photoreceptors. ipRGCs labelled at the top-right.


An ipRGC, shown here as a complied image of the retina from proximal inner nuclear layer to the ganglion cell layer with fluorescent labeling of melanopsin


Spectral sensitivities of the photoreceptors in the human eye. [ 4 ]


Melanopsin structure


Synaptic inputs and outputs of ipRGCs and their corresponding location in the brain


Inputs and outputs to ipRGCs involved in the pupillary light reflex


Section of retina


Rods, cones, and nerve layers in the retina: The front (anterior) of the eye is on the left. Light (from the left) passes through several transparent nerve layers to reach the rods and cones (far right). Chemical changes in the rods and cones send a signal back to the nerves. The signal goes first to the  bipolar  and  horizontal cells  (yellow layer), then to the  amacrine cells  and  ganglion cells  (purple layer), then to the optic nerve fibres. The signals are processed in these layers. First, the signals start as raw outputs of points in the rod and cone cells. Then, the nerve layers identify simple shapes, such as bright points surrounded by dark points, edges, and movement. (Based on a drawing by  Ramón y Cajal , 1911)


Illustration of the distribution of cone cells in the fovea of an individual with normal colour vision (left), and a colourblind (protanopic) retina. The center of the fovea holds very few blue-sensitive cones.


Distribution of rods and cones along a line passing through the fovea and the blind spot of a human eye [ 14 ]


Time-Domain OCT of the macular area of a retina at 800 nm, axial resolution 3 μm


Spectral-Domain OCT macula cross-section scan


Macula histology (OCT)


Fundus photograph  showing the blood vessels in a normal human retina. Veins are darker and slightly wider than corresponding arteries. The  optic disc  is at right, and the  macula lutea  is near the centre.


On-centres and off-centres of the retina


A false-color image of a flat-mounted rat retina viewed through a fluorescence microscope at 50x magnification. The optic nerve was injected with a fluorophore, causing retinal ganglion cells to fluoresce.


Pattern of retinal nerve fibers


Choroid dissected from a calf's eye, showing black RPE and iridescent blue tapetum lucidum


Human eye cross-sectional view grayscale


Anatomy of a Rod Cell [ 7 ]


Wavelength absorbance of short (S), medium (M) and long (L) wavelength cones compared to that of rods (R). [ 12 ]


Gonioscopy  of the anterior chamber angle. Labeled structures: 1. Schwalbe's line, 2.  Trabecular meshwork  (TM), 3.  Scleral spur , 4.  Ciliary body , 5.  Iris


Gonioscopy  of the anterior chamber angle


Superior oblique nerve


A montage of five pictures of the right eye of a male subject with partial heterochromia, demonstrating torsional eye movement


The superior rectus muscle is shown in this image of the right eye from above. Hover the mouse over the structures for their names.  Click for more information.


Gonioscopy  of the anterior chamber angle. Labeled structures: 1.  Schwalbe's line , 2. Trabecular meshwork (TM), 3.  Scleral spur , 4.  Ciliary body , 5.  Iris


Anterior chamber angle cross-section imaged by an  SD-OCT .


Zonules of Zinn visible in a case of an exceptionally dilated pupil with lens subluxation in  Marfan syndrome


Indirect  ophthalmoscopy


Fluorescein angiography


An ophthalmologist performing surgery


Anatomy of the Eye, 1200 A.D.


Early Ophthalmology instruments


New York Ophthalmic Hospital, 1893


Albrecht von Graefe


Allvar Gullstrand


Axial section of the Brainstem (Pons) at the level of the Facial Colliculus


The Clivus


Limitation of  abduction  of the right eye. This individual tries to look to his right, but the right eye fails to turn to the side.


Minimum (top) and maximum accommodation (bottom).


Two horse lenses suspended on water by cling wrap with four approximately parallel lasers directed through them. The 1   cm spaced grid indicates a near focus focal length of around 6   cm


The path of light through the eye calculated using four refractive indexes, cornea and lens curvatures approximating components of real eyes. Note objects in some size ranges and distances do not require the light path to bend noticeably to achieve focus.


Virtual eye showing the contribution to focus of different components.


Schachar model of lens focus


Tracing of Scheimpflug photographs of 20 year old human lens being thicker focusing near and thinner when focusing far. Internal layering of the lens is also significant


Wrinkled lens fibers in picture below compared to straight fibers above


Duane's classical curves showing the amplitude or width of accommodation as changing with age. Mean (B) and approximate lower (A) and upper (C) standard deviations are shown. [ 31 ]


Diving bird (Cormorant) lens focusing can be up to 80 dioptres for clearer underwater vision.


Bony fish eye. Note the harder more spherical lens than in land based animals and a none circular muscle to pull the lens backward


Light from a single point of a distant object and light from a single point of a near object being brought to a focus.


The pupil constricts when accommodation is initiated


Suppression responses


Binocular single vision response


A possible microtropia response


Possible manifest strabismus responses


Photo of someone "palming", from  Perfect Sight Without Glasses .


A  burning glass  being used to focus sunlight on someone's eye, from  Perfect Sight Without Glasses .


Margaret Darst Corbett


Aldous Huxley


Sir  Charles Bell


Blue light, a type of high-energy light, is part of the visible light spectrum


Location of Bjerrum's area, and common types of scotomas.  Bjerrums area is marked with a  dotted blue line  at 25 degrees.


Ophthalmogram  showing blood vessels in front of the  retina . Their shadow is the cause of the blue field entoptic phenomenon.


Bilateral cataracts in an infant due to  congenital rubella syndrome


Post traumatic rosette cataract of a 60-year-old male


Christmas tree cataract (diffuse illumination)


Cross-sectional view, showing the position of the human lens


Cataract surgery, using a temporal-approach phacoemulsification probe (in right hand) and "chopper" (in left hand) being done under operating microscope at the U.S. Navy Medical Center in Portsmouth, Virginia


Slit lamp  photo of posterior capsular opacification visible a few months after implantation of intraocular lens, seen on retroillumination


Slit lamp  photo of anterior capsular opacification visible a few months after implantation of intraocular lens, magnified view


A South African woman experiences newfound eyesight after a patch was removed after surgery to remove an eye cataract.


Disability-adjusted life years  for cataracts per 100,000 inhabitants in 2004: [ 67 ]              no data      <90      90–180      180–270      270–360      360–450      450–540          540–630      630–720      720–810      810–900      900–990      >990


Cherry-red spot as seen here in  Tay–Sachs disease , caused by the  fovea 's center appearing bright red because it is surrounded by a whiter than usual area.


Layers of the eye, with the choroid labelled.


Subspecialities of ophthalmology


Blindness


Basic health services


Congenital cataract in an adult


Alcohol dehydrogenase  immunoreactivity in a healthy cornea (top), in  Fuchs' dystrophy  and  keratoconic  cornea.  Diaminobenzidine  stains keratocytes in the cross-section of cornea. From  Mootha et al., 2009. [ 14 ]


Corneal opacity with  neovascularization


Corneal opacity or "clouding" also gradually appears after death, and can be used to estimate the  postmortem interval  (PMI).


Oculus Pentacam™ Corneal Eye Scan


A Medmont E300 topographer, using a bowl of illuminated rings


Corneal topography showing stage II  keratoconus .


A pair of contact lenses, positioned with the concave side facing upward


Typical pair of single vision glasses


These  bifocals  are upside down as they rest on the surface. The add segment of the lens for near vision is the D-shaped area.


Common lens optical profiles


Constant corrective power with different  base curves  require varying the back surface curvature


Chromatic aberration caused by a convex lens


Prismatic color distortion shown with a camera set for nearsighted focus, and using -9.5 diopter eyeglasses to correct the camera's myopia.


Close-up of color shifting through corner of an eyeglass lens. The visible colored fringing along the light and dark borders between color swatches are not actually on the color chart: They are the result of dispersion of colors by the lens.


Effects of astigmatism


Crude relationship between lens size and its thickness for the same radius of curvature. In addition to its smaller surface area, the small lens is also much thinner and so is much lighter.


The effects of an anti-reflective coating applied (as seen on the bottom picture) as compared to regular eyeglass lens (notice how the reflection of the photographer in the top lens is clearly visible)


Floaters depiction


Purkinje tree depiction


Finnish player of American football wearing eye black


A  peregrine falcon  sitting in a tree, displaying its malar stripes as it watches for  prey .


Close-up image of a  cheetah , showing its malar stripes


Cataract surgery, using a temporal approach  phacoemulsification  probe (in right hand) and "chopper" (in left hand) being done under operating microscope at a Navy medical center


Vitrectomy


Isolating the inferior rectus muscle


Disinserting the medial rectus muscle, after placing vicryl suture


Using a  phoropter  to determine a prescription for eyeglasses


Positive  meniscus lenses  provide positive diopters, while negative meniscus lenses provide negative diopters.


This  phoropter  is set to an axis of 180 for each eye. This can be seen by noticing the tiny white arrows that are horizontal as they point to the tiny numbers that line the opening the patient looks through. Click the image to see a full resolution version where the individual axis markings become more visible.


An eyeglass prescription


1783 etching of wounded sailors


FOV both eyes


Vertical FOV


Angle of view  can be measured horizontally, vertically, or diagonally.


In  computed tomography  ( abdominal CT  pictured), the field of view (FOV) multiplied by  scan range  creates a volume of  voxels .


Field of view diameter in microscopy


Flow of the aqueous humour


Cataract surgery in Bedele, Ethiopia


Cataract operation in São Paulo, Brazil


herpetic blepharitis


Fluorescein-stained cornea: geographic epithelial defects


Impression cytology smear stained by Papanicolaou stain shows the presence of a multinucleated giant cell


Trigeminal shingles with  uveitis  and  keratitis


Herpes zoster ophthalmicus as seen after fluorescence staining using cobalt blue light


Arizona Eye Model. "A" is accommodation in diopters.


A detailed medical illustration of the eye


MRI  scan of the human eye


Schematic diagram of the human eye. It shows a horizontal section through the right eye.


The outer parts of the eye


Side-view of the human eye, viewed approximately 90° temporal, illustrating how the iris and pupil appear rotated towards the viewer due to the optical properties of the cornea and the aqueous humour


The pupil of the human eye can range in size from 2 mm to over 8 mm to  adapt  to the environment


Dilation and constriction of the pupil


The light circle is the  optic disc  where the optic nerve exits the retina


The two eyes converge to point to the same object.


A brown iris


A light brown iris with limbal ring


Amber eye


Hazel eye


Blue eye


Gray eye Northern Italy


Conjunctival infection, or redness of the sclera surrounding the iris and pupil


Diagram of a  human eye  ( horizontal section  of the right eye)  1.  Lens , 2.  Zonule of Zinn or Ciliary zonule , 3.  Posterior chamber  and 4.  Anterior chamber  with 5.  Aqueous humour  flow; 6.  Pupil , 7.  Corneosclera or Fibrous tunic  with 8.  Cornea , 9.  Trabecular meshwork  and  Schlemm's canal . 10.  Corneal limbus  and 11.  Sclera ; 12.  Conjunctiva , 13.  Uvea  with 14.  Iris , 15.  Ciliary body  (with a:  pars plicata  and b:  pars plana ) and 16.  Choroid ); 17.  Ora serrata , 18.  Vitreous humor  with 19.  Hyaloid canal/(old artery) , 20.  Retina  with 21.  Macula or macula lutea , 22.  Fovea  and 23.  Optic disc  →  blind spot ;  24.  Visual axis (line of sight) . 25.  Optical axis . 26.  Optic nerve  with 27.  Dural  sheath, 28.  Tenon's capsule or bulbar sheath , 29. Tendon.  30.  Anterior segment , 31.  Posterior segment .  32.  Ophthalmic artery , 33.   Artery  and  central retinal vein  → 36. Blood vessels of the retina;  Ciliary arteries  (34.  Short posterior ones , 35.  Long posterior ones  and 37.  Anterior ones ), 38.  Lacrimal artery , 39.  Ophthalmic vein , 40.  Vorticose vein .  41.  Ethmoid bone , 42.  Medial rectus muscle , 43.  Lateral rectus muscle , 44.  Sphenoid bone .


Ewald Hering's model, published 1899, of how a Vernier acuity stimulus is coded by a receptor array. Receptors marked  c  signal a different position code along the horizontal direction from either the position  a  code or the position  b  code. [ 1 ]


Acuity/Resolution versus Hyperacuity/Localization  Top: Two stars imaged on the mosaic of retinal receptor cells can be resolved only if their separation leaves at least one intervening mosaic element with a detectably different intensity, otherwise the pattern is indistinguishable from a single elongated star.  Bottom:  Two targets can be localized relative to each other to values transcending the spacing of the mosaic units; the hyperacuity mechanism achieves this by identifying,  with sub-pixel precision, the light center of each target, across all the pixels it covers


A seven-week-old human baby following a kinetic object.


Infants' eyes develop significantly after birth.  The muscles of the eye such as  ciliary  muscles – become stronger after two months of age, allowing infants to focus on particular objects through contraction and relaxation. Their retinal images are also smaller compared to adults due to shorter distances from the  retina  to the  cornea  of the infants' eye. [ 1 ]  A newborn's  pupil  grows from approximately 2.2 mm to an adult length of 3.3 mm. [ 2 ]


Infants are often attracted to shiny bright objects with strong contrast and bold colors.


Eighth International Ophthalmological Congress, Edinburgh, Scotland. 1894


A phakic IOL


Before surgery (natural crystalline lens, left). After surgery (implanted PCIOL, right).


An anterior chamber IOL (ACIOL)


A posterior capsular opacity (PCO) around a posterior chamber IOL (as seen on retroillumination in a  slit lamp )


Acrylic MICS-IOL in holder


Plaque at  St Thomas' Hospital  – site of first permanent insertion of an intraocular lens, 8 February 1950


A patient in front of a  tonometer


Diaton transpalpebral tonometer


Anatomical diagram of a human eye


An anatomical diagram of the human eye, showing vitreous humor in the vitreous chamber.


A photo of a right eye divided into 4 quadrants: superotemporal, superonasal, inferotemporal, and inferonasal.


An anatomical diagram showing the limbus of the eye.


Diagram describing the IOLVIP procedure


Boston Kpro type 1 titanium posterior plate


Ketorolac package from Russia


Landolt C optotypes in various sizes and orientations


Golovin–Sivtsev table


The localization of limbal epithelial stem cells and the anatomy of the cornea. LESC: limbal epithelial stem cell.From a review by Ruan et al., 2021. [ 9 ]


Yaw, pitch, roll.


Miosis caused by high doses of  opiates . The person also shows  ptosis  of both eyelids and an inattentive look at the camera, a sign of  altered level of consciousness  caused by the sedative effect of the drug.


A person wearing mirrored sunglasses


Supreme Court Police  officer wearing wraparound mirrored sunglasses in Washington, DC


Track cyclist  Yuta Wakimoto  wearing a helmet with a mirrored visor


Both pupils are dilated (mydriasis) because of hyper-activation of the  sympathetic system  caused by the psychedelic drug  LSD


Mydriasis with the pupil dilated to 9mm in diameter as a result of dim lighting. Most individuals are not able to achieve pupillary dilation to this extent without mydriatic agents


Nd:YAG laser with lid open showing frequency-doubled 532 nm green light


Nd:YAG laser rod


Neodymium ions in various types of ionic crystals, and also in glasses, act as a laser gain medium, typically emitting 1064 nm light from a particular atomic transition in the neodymium ion, after being "pumped" into excitation from an external source


Slit lamp  photograph of posterior capsular opacification visible a few months after implantation of intraocular lens in eye, seen on retroillumination


Military surplus Nd:YAG laser rangefinder firing. The laser fires through a collimator, focusing the beam, which blasts a hole through a rubber block, releasing a burst of plasma.


Duane's classical curves showing the amplitude or width of accommodation as changing with age. Mean (B) and approximate lower (A) and upper (C) standard deviations are shown. [ 1 ]


Snellens near vision chart


Nummular Keratitis, a feature of the chronic phase of  adenoviral keratoconjunctivitis


Human ocular prosthesis of brown color.


Cat with an ocular prosthesis.


Prosthetic eye and glasses made for an injured  World War I  soldier by pioneering plastic surgeon  Johannes Esser .


"Making glass eye",  c.  1915–1920 .


Glass eye being moulded under heat, 1938.


An Arabic manuscript, dated 1200 CE, titled  Anatomy of the Eye , authored by  al-Mutadibih


Ruete's Ophthalmotrope 2nd model, 1857


A  fundus photograph  showing the back of the retina. The white circle is the beginning of the optic nerve.


One of Wilhelm Kühne's rabbit optograms from 1878. The window the rabbit was facing appears to be discernible in the image.


Line drawing by Wilhelm Kühne of the only "human optogram", an image from the retina of executed prisoner Erhard Gustav Reif.


CT scan  taken from the  transverse plane  demonstrating orbital emphysema. [ 39 ]


CT scan  taken from the  coronal plane  demonstrating orbital emphysema. [ 39 ]


Public education poster urging eye exams for children ( Works Progress Administration , circa 1937)


Image formation in a  confocal microscope : central longitudinal (XZ) slice. The 3D acquired distribution arises from the  convolution  of the real light sources with the PSF.


A  point source  as imaged by a system with negative (top), zero (center), and positive (bottom)  spherical aberration . Images to the left are  defocused  toward the inside, images on the right toward the outside.


Application of PSF: Deconvolution of the mathematically modeled PSF and the low-resolution image enhances the resolution. [ 2 ]


Square Post Function


Truncation of Spherical Wave by Lens


Airy disk


An example of an experimentally derived point spread function from a confocal microscope using a 63x 1.4NA oil objective. It was generated using Huygens Professional deconvolution software. Shown are views in xz, xy, yz and a 3D representation.


The point spread function of  Hubble Space Telescope 's  WFPC  camera before corrections were applied to its optical system.


Overlapped PSF peaks.  When the peaks are as close as ~ 1 wavelength/NA, they are effectively merged. The FWHM is ~ 0.6 wavelength/NA at this point.


The Prentice position


Prism lenses (here unusually thick) are used for pre-operative prism adaptation.


Monocular PD can be measured during an eye test.


PD measurement using an app (PD+ by Zernike)


Pupillary distance measurement with iPad app


Variation in the size of the pupil in bright (left) and dim (right) environments. In this case the pupil is 3 mm in diameter on the left, and 9 mm on the right


Pathways in the  Ciliary ganglion .      Parasympathetic;      Sympathetic;      Sensory


Schematic diagram of pupillary light reflex neural pathway


A medical  halogen penlight  used to observe pupillary light reflex.


Diagram illustrating the locations of extraocular muscles and ocular cranial nerves. Paresis of the oculomotor nerve (CNIII) reduces the strength of  medial rectus ,  superior rectus ,  inferior rectus , and  inferior oblique  muscles, while trochlear nerve (CNIV) and abducens nerve (CNVI) paralysis affect  superior oblique muscle  and  lateral rectus muscle  respectively.


Physical examination showing ophthalmoplegia affecting the left eye. The central image represents forward gaze while other images represents different direction of gaze. Drooping of eyelids  (ptosis ) and nonaligned eyes ( strabismus ) are observed, showing paresis of CNIII, CNIV and CNVI.


Diagram of the eye highlighting the retina, vitreous humor, and other key structures.


Visual representation of eye floaters seen against a blue sky


Fundus photograph showing a retinal detachment


Ultrasound showing a retinal detachment


Rheum from a cat's eyes


Rose bengal solid and solution in water


Optical microscopy image of the undescribed species of  Spinoloricus  from  Loricifera  stained with rose bengal.


rose bengal disodium salt


Before Brucella Rose Bengal Test application


After Brucella Rose Bengal Test application


Shooting glasses are used as a visual aid for sport shooting. Though the glasses are extremely customizable, most pairs contain three basic elements: a lens, a mechanical iris, and a semi-transparent occluder. These components work together to help shooters focus their aiming eye on three points well enough to align the distant target with their gun's front and rear sight elements at the same time.


True Sloan letters as described in the original article of Louise L. Sloan (1959).


Solar eclipse glasses.


The  solar eclipse of December 26, 2019  seen through a pair of solar eclipse glasses in  Jaffna , Sri Lanka.


A cat demonstrating a pair of eclipse glasses.


3-angle spirangle or triangle spiral


Ulam spiral  in a 4-angle spirangle or rectangle spiral


7-angle spirangle or heptagon spiral


70-angle spirangle


Eye patches may strengthen the weaker eye but fail to stimulate binocular vision and stereopsis, which may sometimes be recovered by different means.


Oliver Sacks  was the first to make the story of Susan Barry, whom he nicknamed "Stereo Sue", known to the general public.


Although stereoblind, Bridgeman used polarized glasses in a 3D cinema and could suddenly see in 3D.


Tetris  is a popular video game from the 1980s. A modified version of the game (not shown here) has been used for dichoptic training.


Prism lenses (here unusually thick) are used for pre-operative prism adaptation.


Howard-Dolman test.


Example of a Snellen-like depth test


X-ray showing  metacarpophalangeal  subluxation of the thumb of a 71-year-old woman due to  trapeziometacarpal osteoarthritis


Wearing sunglasses under direct sunlight: Large lenses offer good protection, but broad temple arms are also needed against "stray light" from the sides.


Inuit   snow goggles  function by reducing exposure to sunlight, not by reducing its intensity


Antoine Lavoisier  conducting an experiment related to combustion generated by amplified sun light


Effect of pair of polarized filters


Broad temple arms protect against "stray light" entering from the sides.


These safety sunglasses have a scratch resistant coating, block 99.9% UV, and meet ANSI Z87.1 and CSA Z94.3 standards.


Protecting his eyes from exposure due to  exophthalmos , sunglasses have become the trademark of German singer  Heino .


Artist  Elize Ryd  wearing sunglasses as part of her costume for the  Tuska Open Air Metal Festival


As of 2009, the European  CE mark  indicates that the glasses actually offer a certain level of sun protection.


Hunter S. Thompson  was known for wearing yellow-tinted driving glasses.


Sunglasses worn by an  ocean kayaker


A  Sherpa   mountain guide  on an expedition to  K2  (8.611 m), wearing anatomically shaped mountaineering sunglasses


2006: Swedish astronaut  Christer Fuglesang  wears glasses during a construction mission for the  International Space Station .


A range of sunglass models with lenses of different colors, for sale in  New York City


Different reflection characteristics and variations in glass  stress  are demonstrated when photographed through a polarizing lens (bottom picture).


This sunglass eyeshield uses a nylon half-frame and interchangeable lenses.


Aviator sunglasses


A  Bengali  man sporting aviator sunglasses


Oversized sunglasses à la Jackie O


Teashade sunglasses


Original  Ray-Ban Wayfarer


Mirrored wrap-around sunglasses


Clip-on sunglasses


Glasses with gradient lenses


Mirrored aviators


Healthy eye fundus viewed through a retinal camera


Retinal image with signs of macular degeneration


A non- mydriatic   Topcon  retinal camera


The Cavernous Sinus


Animated vernier scale (“Nonius”): The lower rectangle is divided into 10 sections but is equal in length to 9 sections in the upper scale. It is used, e.g., in a  vernier caliper .


Eye examination for visual acuity


The  LogMAR – ETDRS Chart , designed in 1976, to test for visual acuity


Manual hand eye test in Ghana (2018)


The diagram shows the relative acuity [ 26 ]  of the human eye on the horizontal meridian.  [ 27 ] [ 4 ] [ 28 ]   [ dubious  –  discuss ]  The  blind spot  is at about 15.5° in the outside direction (e.g. in the left visual field for the left eye). [ 29 ]


The classical image on the shape and size of the visual field by Harry Moss Traquair in his book  Clinical Perimetry  (1938; modified to show the essentials). It shows that the visual field is considerably larger on the temporal side than the often quoted 90° extent. Similar limits were already reported in the 19th century.


Bjerrum's area and types of scotomas on the visual field


Visual pathway lesions    From top to bottom:   1. Complete loss of vision in the right eye   2. Bitemporal hemianopia   3. Homonymous hemianopia   4. Quadrantanopia   5. & 6. Quadrantanopia with  macular sparing


Visual field-tubular vision


Visual field-central scotoma


Visual field-bitemporal hemianopia


Visual field-binasal hemianopia


Visual field-homonymous hemianopia


Visual field-right superior quadrantanopia


A bifocal lens with areas of differing magnification


Bifocals with separate lenses. In this case, the Swedish ethnologist  Jan-Öjvind Swahn  [ sv ] .


A pair of contact lenses, positioned with the concave side facing upward


One-day  disposable  contact lenses with blue handling tint in blister-pack packaging


Artist's impression of  Leonardo's  method for neutralizing the refractive power of the cornea


In 1888,  Adolf Gaston Eugen Fick  was the first to successfully fit contact lenses, which were made from blown glass


Otto Wichterle  (pictured) and  Drahoslav Lím  introduced modern soft hydrogel lenses in 1959.


Woman wearing a cosmetic type of contact lens; enlarged detail shows the grain produced during the manufacturing process. Curving of the lines of printed dots suggests these lenses were manufactured by printing onto a flat sheet then shaping it.


Scleral lens , with visible outer edge resting on the sclera of a patient with severe  dry eye syndrome


Non-cosmetic contact lenses become almost invisible once inserted in the eye. Most corrective contact lenses come with a light "handling tint" that renders the it slightly more visible on the eye, sometimes visible against the  sclera .


Molecular structure of silicone hydrogel used in flexible, oxygen-permeable contact lenses. [ 70 ]


Diameter and base curve radius


Lens case to store contacts


Contact lenses soaking in a hydrogen peroxide-based solution.


Saline solution bottles together with contact lens cases


Contact lens acute red eye  (CLARE) is a group of inflammatory complications from lens wear


Christopher Lee  as the title character in  Dracula  (1958) in one of the first uses of contact lens with makeup in films


Man with glasses.


A woman with glasses


A  skyline  seen through a corrective lens, showing the effect of  refraction


Microfiber cloth  designed for cleaning corrective lenses without scratching sensitive glass


1940s combined hearing aid glasses, on display at  Thackray Museum of Medicine . [ 2 ]


Safety glasses  with side shields


Woman wearing  sunglasses


Double-frame eyewear with one set of lenses on the moving frame and another pair of lenses on a fixed frame (optional).


McKie Reid recumbent glasses, on display at  Thackray Museum of Medicine . [ 8 ]


Glasses,  c.  1920s , with springy cable temples


Modern glasses with a rectangular lens shape


The  Glasses Apostle  by  Conrad von Soest  (1403)


Seated apostle holding lenses in position for reading. Detail from  Death of the Virgin , by the  Master of Heiligenkreuz ,  c.  1400 –1430 ( Getty Center ).


French Empire gilt  scissors glasses  (with one lens missing),  c.  1805


Man wearing glasses on the 16th century  Ming dynasty   Chinese painting   The Bustling and Hustling of Nanjing  ( zh:南都繁会图 )


Woman wearing eyewear with non-prescription lenses in a fashion  photo shoot .


Glasses - Decoration, Prezi HQ, Budapest


Former United States senator  Barry Goldwater  in  horn-rimmed glasses


Joseph Chamberlain  wearing a monocle


A 20th-century  gold plated  monocle with gallery


Field Marshal  Hugo Sperrle  wearing a monocle


Orthokeratology lens


An installed PIOL, with flash photography


An installed PIOL, without flash photography


A photochromic eyeglass lens, part of the lens darkened after exposure to sunlight while the other part remained covered


Anton Chekhov  with pince-nez, 1903


C-bridge pince nez spectacles, cased, England, between 1875 and 1925


Rimless astig pince-nez


Finger-piece hard bridge pince-nez


Pince-nez hard bridge (top) and Oxford spectacles (bottom) compared


Erik Satie  wearing pince-nez


View through a progressive lens at some distance. In normal use, a much smaller section of the lens is used, so that the distortion is much smaller.


Reading stone in  Archeon , a historical theme park


Top: farsighted corrected using convex lens Bottom: nearsighted corrected using concave lens.


Fundus of person with  retinitis pigmentosa , early stage


A doctor uses a trial frame and trial lenses to measure the person's refractive error.


DALYs  per 100,000 people due to refractive errors in 2004. [ 46 ]      No data      Less than 100      100–170      170–240      240–310      310–380      380–450      450–520      520–590      590–660      660–730      730–800      More than 800


Scleral lens, with visible outer edge resting on the sclera of a patient with chronic severe dry eye syndrome.


Scleral lens prescribed for dry eye, on a removal plunger


Toric lens surface as  "cap" (top-right) from a torus (here with  R  = 1.2  r ).


A torus results when a circle with  radius   r  rotates around an axis lying in the same plane as the circle (here the  z  axis) at a distance  R  from the centre of the circle.


When the major radius  R  approaches 0 (here from right to left), the torus becomes a sphere.


French Varilux Logo


Vertex distance


Corrected and uncorrected spherical power for a vertex distance of 12   mm.


Difference in spherical power at a vertex distance of 12   mm versus 0   mm.


Eduard Jäger von Jaxtthal (1818-1884)


Friedrich Jäger von Jaxtthal, 1827


Anton von Rosas; (1834  lithograph  by  Josef Kriehuber ).


Grave of Anton von Rosas at  St. Marx Cemetery ,  Vienna


Altered vision by SOM during daylight driving.


Altered vision by SOM during night driving.


When light enters one eye, it is detected by retinal photoreceptors and transmitted via the optic nerve to the pretectal nucleus in the midbrain. From there, signals are sent bilaterally to the Edinger-Westphal nuclei, which send parasympathetic fibers via the oculomotor nerves to the ciliary ganglia. These fibers innervate the sphincter pupillae muscles in both eyes, causing both pupils to constrict—the direct response in the stimulated eye and the consensual response in the other eye. This bilateral response ensures equal pupillary adjustment to light.


A pair of CrystalEyes shutter glasses


Functional principle of active shutter 3D  systems


SegaScope 3-D Glasses , released in 1987


Famicom 3D System , released in 1987 for Japan only


Browline glasses


Malcolm X  wearing browline glasses, of which he owned several pairs, each in different colours


Ray-Ban  3016 Clubmaster sunglasses


Paris Hilton  wearing bug-eye glasses


Woman wearing cat eye glasses in the 1960s


Dr.  Otto Wichterle  wearing a male version of cat eye glasses


1911 newspaper story on chicken eyeglasses from the  Spirit Lake Beacon  (Iowa) [ 1 ]


Detail from a 1903 patent filed by Andrew Jackson Jr.


A plate from the  Ishihara test


Transmittance of various monocular color correcting lenses superimposed onto the normalized spectral sensitivities of the cone opsins of a color normal observer.


Transmittance of tinted color correcting lenses (Vino and ColorMax) superimposed onto the normalized spectral sensitivities of the cone opsins of a color normal observer.


Transmittance of EnChroma color correcting lenses (indoor and outdoor) superimposed onto the normalized spectral sensitivities of the cone opsins of a color normal observer.


Google Glass has been used with daltonization filters to create a sort of "active" color correcting lens


Transmittance of the Variantor colorblind simulation lens superimposed onto the normalized spectral sensitivities of the cones.


GI glasses, gray cellulose acetate, 1960s design


Army issue glasses from the mid-1980s


Male S9 ("MS9") GI glasses, 1990s design


Female S9 ("FS9") GI glasses


Model "5A" GI glasses, 2012 design


Woman wearing a pair of Groucho glasses


A pair of horn-rimmed glasses


Comparison of  browline  (left) and wayfarer horn-rimmed glasses, with prescription lenses for myopia


A woman wearing lensless glasses


Folding set of Lorgnette spectacles,  Bedford Museum, Bedford .


Lorgnette used by  David Scott Mitchell


Fan lorgnette from late 18th century


Portrait of Louise von Wertheimstein holding a lorgnette


A pair of New Year's glasses for 2009. The chassis is made up of the  00  digits in the year.


Mother of pearl  opera glasses and leather case.


Opera glasses with handle, ca.1910


An example of contemporary, pressure-mounted three-piece rimless eyeglasses


President Theodore Roosevelt in rimless  pince-nez . Photos of Roosevelt wearing the glasses led to the initial popularization of rimless eyeglasses amongst Americans in the early 1900s.


French Empire  gilt scissors-glasses c. 1805


The  Glasses Apostle  by  Conrad von Soest  (1403)


Replication medieval scissors-glasses


A branch of Specsavers (with older signage) in the Horsefair Centre in  Wetherby ,  West Yorkshire .


Specsavers store along the Kauppurienkatu street in  Oulu, Finland


Mahatma Gandhi's glasses in the  National Gandhi Museum


The Brushfield spots are the spots between the inner and outer red circles.


An eye with a swollen region of the conjunctiva (front view).


An eye with a swollen region of the conjunctiva (mirror, side view).


Close-up of a cherry eye


Beagle-cocker spaniel mix with cherry eye


Close-up of prolapsed gland in small breed dog


CEV noise simulation


CEV noise simulation with multiple colors (Purple, Green, Yellow)


CEV noise simulation with multiple colors and flashing dot


Level 3 CEV simulation without noise


CEV noise simulation with disappearing flashing image


Level 5 CEV simulation


Iris coloboma in the right eye of a 10-month-old child. The pupil cannot contract to a smaller size than pictured, but may still be able to dilate in low light.


Figure 1.  Schematic structure of Ca V 1.4 with the domains and subunits labeled.


Bloodshot eyes


Viral conjunctivitis


An eye with  allergic conjunctivitis  showing conjunctival edema


An eye with bacterial conjunctivitis


Typical membranous conjunctivitis


An eye with chlamydial conjunctivitis


The procedure of conjunctival swabs


Central Descemet's membrane rupture with inferocentral corneal edema (hydrops).


Large corneal ulcer in a dog


A corneal ulcer in a cat


Refractory corneal ulcer


Macular hard drusen in the right eye. 65-year-old diabetic woman.


Drusen in  optical coherence tomography .


Exposure keratitis


Tape being removed off eye


Tape awaiting placement


Fig.1: Visual axes of the two eyes in optimal binocular vision (blue) and in exo and eso fixation disparity (black and red, respectively).


Fig. 2: Definition of the two types of fixation disparity


Fig. 3: Fixation disparity as a function of the forced vergence angle which is induced by base-in prisms and base-out prisms in front of the eyes.


Fundus of geographic atrophy


Intermediate magnification  micrograph  showing giant cell arteritis in a  temporal artery  biopsy. The arterial lumen is seen on the left. A giant cell is seen on the right at the interface between the thickened  intima  and  media .   H&E stain


Histopathology of giant cell vasculitis in a cerebral artery. Elastica-stain.


Magnetic resonance imaging of the orbits, showing congestion of the retro-orbital space and enlargement of the  extraocular muscles  (arrows), consistent with the diagnosis of Graves' ophthalmopathy.


Domestic cat with complete heterochromia, also referred to as an  odd-eyed cat .


Congenital heterochromia: inherited in  autosomal dominant  fashion (from men or women)


Individual with  Waardenburg Syndrome  Type II exhibiting complete heterochromia iridum


An  Alaskan husky  sled dog with heterochromia. Huskies are a breed known to have a high incidence of heterochromia.


Sectoral heterochromia


Central heterochromia, green with brown


A  Turkish Angora  cat with complete heterochromia.


Fundus photograph of right retina with labelled ischemic area and cholesterol embolus (“Hollenhorst plaque”)


Right eye findings. a Fundus photo showing superior pale retina. b Presence of Hollenhorst plaque in the superotemporal vessel (arrow)


Scheme showing sympathetic and parasympathetic innervation of the pupil and sites of a lesion in Horner's syndrome.


Left-sided Horner's syndrome in a cat as a result of trauma, demonstrating miosis in left pupil.


Slit lamp view of hypopyon


Ultrasound of the optic nerve showing IIH [ 17 ]


A  lumbar puncture  in progress. A large area on the back has been washed with an  iodine -based disinfectant leaving brown colouration. In this image the person is seated upright, which can make the procedure easier to perform but makes any measurement of the opening pressure unreliable.


The number of new cases per year of IIH is strongly determined by sex and  body weight . The figures in females are in women between 20 and 45 years old. [ 5 ]


Breakdown of diagnosis in orbital lymphoproliferative disorders in a Japanese study [ 1 ]


Enlargements in the left  inferior rectus muscle  and  infraorbital nerve   (arrow)  in a 65-year-old man with a serum IgG4 of 404 mg/dL. [ 1 ]   (T2-weighted MRI)


Swelling of the left  superior  and  lateral rectus muscles , a mass lesion around the left  optic disc   (arrow) , and enlargements of the left  supraorbital nerve  and the right  infraorbital nerve   (arrow heads)  in a 60-year-old man with a serum IgG4 of 463 mg/dL. [ 1 ]   (T1-weighted MRI)


Bilateral  supraorbital nerve  enlargements  (arrows)  and right  infraorbital nerve   (arrow head)  enlargement in a 47-year-old woman with a serum IgG4 of 1000 mg/dL. [ 1 ]   (T1-weighted MRI)


Simulation of the  multiple images  seen by a person with keratoconus.  "... a candle, when looked at, appears like a number of lights, confusedly running into one another" — Nottingham [ 12 ]


Multiple images made by extremely high contrast light sources as seen by a person with keratoconus


A specimen of keratoconic cornea taken out six years after diagnosis: thin stroma, wrinkled posterior surface


A schematic diagram showing change in  cornea


Corneal topographer, used for mapping the surface curvature of the cornea


Corneal topography showing stage II keratoconus


Rigid gas permeable (RGP) lens


Scleral lens


Corneal transplant for keratoconus, approximately one week after surgery – multiple light reflections indicate folds in the cornea that later resolved


Cornea transplant after one year of healing; two stitches are visible


A pair of Intacs after insertion into the cornea


Diagram of MARK incisions


A small rupture of  Descemet's membrane  (magnified view)


Corneal hydrops due to keratoconus


Practical observations on conical cornea , Nottingham's ground-breaking text on keratoconus, 1854


Loa loa  life cycle. Source: CDC


Human retina cross-section


Diagram of the human eye showing macula and fovea


Cystoid Macular Oedema in patient with MacTel type 1


Fundoscopy demonstrating age-related macular degeneration.


Meibomian glands in the lower eyelid imaged under amber light to show vasculature support and the gland structure.


Classification of MGD


Amsler grid as it might appear to someone with micropsia as a result of  age-related macular degeneration .


An  MRI  image of a brain tumor occupying the left  temporal  and  parieto - occipital  regions of the brain.


Nuclear sclerosis


Nystagmus as seen in a case of  ocular albinism


Fast-phase horizontal eye movement vision


Fast-phase vertical eye movement vision


A diagram of the  caloric reflex test , which tests the  vestibulo-ocular reflex  (VOR) by irrigating the ear canal with warm or cold water to induce physiological nystagmus.


Large optic pit (fluorescein angiography)


Central serous chorioretinopathy (pachychoroid stage II) with subretinal fluid (black triangle in the middle) and a markedly thickened, congested choroid (white arrowheads).


Weiss ring: a large, ring shaped floater that is sometimes seen if the vitreous body releases from the back of the eye


Diagram of  anterior segment  of a  human eye  ( horizontal section  of the right eye)  1.  Lens , 2.  Zonule of Zinn or ciliary zonule , 3.  Posterior chamber  and 4.  Anterior chamber  with 5.  Aqueous humour  flow; 6.  Pupil , 7.  Corneosclera  with 8.  Cornea , 9.  Trabecular meshwork  and  Schlemm's canal . 10.  Corneal limbus  and 11.  Sclera ; 12.  Conjunctiva , 13.  Uvea  with 14.  Iris , 15.  Ciliary body .


Conventional surgery to treat glaucoma makes a new opening in the meshwork. This new opening helps fluid to leave the eye and lowers intraocular pressure.


In a surgical procedure called  trabeculectomy , the trabecular meshwork is removed to help glaucoma patients.


Pseudostrabismus in a Korean child


Hyphaema  – showing blood filling the anterior chamber, causing a horizontal fluid level


Acute glaucoma, angle closure type


Eye with iritis showing ciliary flush


Anatomy of the human eye


Phenotypic appearance in patients with sclerocornea, aphakia, and microphthalmia.


Vertebrate eye development (human eye). (A) During early vertebrate development, the eye field is established at the boundary between the telencephalon (brown) and the diencephalon (green). (B) Optic vesicles bilaterally protrude from either side of the forebrain approaching the thickened surface ectoderm (lens placodes). (C) The interaction between the optic vesicle and the lens placode of the surface ectoderm results in optic vesicle invagination, optic cup formation and lens placode evagination (lens pit). Simultaneously, the optic fissure is formed along the inferonasal aspect of the optic cup, which surrounds the hyaloid artery. (D) Continued evagination of surface ectoderm leads to the formation of an independent lens vesicle.


Penetrating keratoplasty. The goal is improve the vision or if not, restore the integrity of the ocular globe


Slit lamp exam


(C) Peters anomaly shows central corneal opacification (black arrows) reflecting the abnormal separation of the lens vesicle from the surface ectoderm looking similar to scleracornea


RAD21 has many roles including DNA damage repair, transcription regulation, DNA replication, and centrosome biogenesis, etc. Diseases rise when mutations in RAD21 disrupt its function (in green).


Anterior staphyloma after fungal corneal ulcer.


Ciliary Staphyloma


Posterior staphyloma  inferior  to the  optic nerve  (right eye)


A man sungazing


Diagram showing the definition of telecanthus, or dystopia canthorum


Eye anatomy


Ellis Island  Public Health Service  physicians examining new immigrants for trachoma in 1910


Disability-adjusted life year  for trachoma per 100,000 inhabitants in 2004             no data      ≤10      10–20      20–40      40–60      60–80      80–100          100–200      200–300      300–400      400–500      500–600      ≥600


The burden of  onchocerciasis : children leading blind adults in Africa


Re-educating wounded. Blind French soldiers learning to make baskets, World War I.


Tommy Edison , a blind film critic, demonstrates for his viewers how a blind person can cook alone.


Folded long cane


A blind man is assisted by a  guide dog  in Brasília, Brazil.


Blind girl feels shape of vehicle near  Mana village, Uttarakhand .


Visually impaired girl negotiating a rock while rock climbing


Braille watch


A  tactile feature  on a  Canadian banknote


Scaled-down palpable model of mountain for blind tourists


Blind Woman  by  Diego Velázquez


The Sense of Touch  by  Jusepe de Ribera  depicts a blind man holding a marble head in his hands.


Uveitis  with  poliosis  of the eyelashes


A lens dislocation caused by Weill-Marchesani syndrome


Carbonic anhydrase ( ribbon ) complex with a sulfonamide inhibitor ( ball-and-sticks )


Proximal convoluted tubule. Urinary space is on left.


Acetylcholine pathway.


Acetylcholine processing in a synapse. After release acetylcholine is broken down by the enzyme  acetylcholinesterase .


Muscles contract when they receive signals from motor neurons. The neuromuscular junction is the site of the signal exchange. The steps of this process in vertebrates occur as follows: (1) The action potential reaches the axon terminal. (2) Calcium ions flow into the axon terminal. (3) Acetylcholine is released into the  synaptic cleft . (4) Acetylcholine binds to postsynaptic receptors. (5) This binding causes ion channels to open and allows sodium ions to flow into the muscle cell. (6) The flow of sodium ions across the membrane into the muscle cell generates an action potential which induces muscle contraction. Labels: A: Motor neuron axon B: Axon terminal C: Synaptic cleft D: Muscle cell E: Part of a Myofibril


Components and connections of the  parasympathetic nervous system .


Micrograph  of the  nucleus basalis  (of Meynert), which produces acetylcholine in the CNS.  LFB-HE stain .


Blood flow obstructed by coagulated blood that could potentially be reversed with alteplase.


Depiction of the pathway that alteplase (t-PA) uses to promote the degradation of a blood clot (fibrin).


Artificial tear usage


An  ampoule  containing atropine injection 0.5mg/1mL


Atropa belladonna


Bimatoprost is used cosmetically to increase eyelash prominence


Bromfenac  lactam , the main metabolite in urine


Chemical structures of diclofenac, bromfenac, nepafenac, and amfenac.


Cyclosporin biosynthesis. Bmt = butenyl-methyl-threonine, Abu = L-alpha-aminobutyric acid, Sar = sarcosine


Ciprofloxacin 250-mg tablets from Ukraine


Clonidine tablets and transdermal patch


Structural comparison between the neurotransmitter norepinephrine and the drug clonidine. Both drugs bind to α 2  adrenergic receptors. [ 85 ]  Similarities between the two structures are shown highlighted in red.


Pupil dilation ( mydriasis ) caused by cyclopentolate 1% instilled into both eyes


Reaction of the DIFP with a serine protease


Crystal structure of Herpes Simplex Virus Protease/Inhibitor (DFP) complex. The active site serine (yellow) has undergone phosphonylation resulting in irreversible inhibition. Rendered from PDB  1AT3 .


Ephedrine Sulphate (1932), Ephedrine Compound (1932), and Swan-Myers Ephedrine Inhalant No. 66 ( circa  1940).


The four stereoisomers of ephedrine.


Ephedrine tablets.


Proposed biosynthetic pathway of ephedrine from  L -phenylalanine and pyruvic acid. [ 88 ] [ 89 ]


Epinephrine vial 1 mg (Adrenalin).


Metal–EDTA  chelate  as found in Co(III) complexes


Structure of [Fe(EDTA)(H 2 O)] − , showing that the EDTA 4−  ligand does not fully encapsulate  Fe(III) , which is seven-coordinate [ 27 ]


Guaiazulene solution in DMSO with hydroquinone added as an antioxidant


The blue color of the mushroom  Lactarius indigo  is due to the guaiazulene derivative (7-isopropenyl-4-methylazulen-1-yl)methyl stearate. [ 2 ]


A vial of heparin sodium for injection


Heparin vial for subcutaneous injection


Ball-and-stick model  of heparin


IdoA(2S)-aMan: The anhydromannose can be reduced to an anhydromannitol


Wobble base pairs for  inosine  and  guanine


Latanoprost eye drops, marketed by Pfizer


Latanoprost in Japanese-language packaging


Metabolism . From left to right: latanoprost, latanoprost acid (the  active metabolite ), 1,2-dinorlatanoprost acid, 1,2,3,4-tetranorlatanoprost acid [ 15 ]


Dihydrolevobunolol, the  metabolite , which has equal activity to levobunolol [ 2 ]


Hydrocortisone


Loteprednol etabonate


Nandrolone, with the differences from testosterone highlighted in red. The  methyl group  in testosterone at the C19 position has been removed, and the C17β position is where esters are attached to nandrolone.


19-Nortestosterone synthesis: [ 48 ]  alternative: [ 49 ] [ 50 ]


QV Nandrolone Deca, a form of nandrolone used by athletes.


Red eyes can be treated with naphazoline.


AR-13503, the  active metabolite


The two  enantiomers  of the ofloxacin molecule, levofloxacin or  S -ofloxacin (top) and dextrofloxacin or  R -ofloxacin (bottom). Only levofloxacin is biologically active, and is thus solely responsible for the effects of the drug.


Bepanthen eye and nose ointment (Germany)


A vial of nasal spray containing panthenol, manufactured in Italy


Dexpanthenol


First total synthesis of physostigmine  Julian & Pikl (1935)


Physostigmine proposed biosynthesis


Pheochromocytoma  seen like a dark sphere in center of the body. Image is by  MIBG   scintigraphy  with radiation from  radioiodine  in the MIBG. Note unwanted uptake of radioiodine from the pharmaceutical by the thyroid gland in the neck, in both images (front and back) of the same patient. Radioactivity is also seen in the bladder.


Distribution areas for iodine pills in the Netherlands (2017).


Prevalence of vitamin A deficiency in 1995


Vitamin A biosynthesis


β-ionone ring


Frederick Gowland Hopkins, 1929 Nobel Prize for Physiology or Medicine


George Wald, 1967 Nobel Prize for Physiology or Medicine


Riboflavin is the biosynthetic precursor of FMN and FAD


Cultures of  Micrococcus luteus  growing on pyridine (left) and succinic acid (right). The pyridine culture has turned yellow from the accumulation of riboflavin. [ 16 ]


The biochemistry of tropane class compounds.  Hyoscyamine  and scopolamine are present and labeled.


Figure 4: Proposed mechanism of lysine cyclodeaminase conversion of L-lysine to L-pipecolic acid


A plaque, written in Portuguese, commemorating the discovery of sirolimus on Easter Island, near  Rano Kau


Mounds of road salt for use in winter


A class-D fire extinguisher for various metals


Sodium chloride crystal under microscope.


NaCl octahedra. The yellow stipples represent the electrostatic force between the ions of opposite charge


View of one slab of  hydrohalite , NaCl·2H 2 O. (red = O, white = H, green = Cl, purple = Na). [ 28 ]


Phase diagram of water–NaCl mixture


Metabolism . From left to right: tafluprost, tafluprost acid (the  active metabolite ), 1,2-dinortafluprost acid, 1,2,3,4-tetranortafluprost acid, 1,2,3,4-tetranortafluprost acid lactone [ 5 ] [ 6 ]


A tafluprost/ timolol  combination ophthalmic solution


One 2.5 ml dropperette of Travatan


Metabolism . From left to right: travoprost, travoprost acid (the  active metabolite ), 1,2-dinortravoprost acid, 1,2,3,4-tetranortravoprost acid. Below: reduction of the 13,14-double bond (red) and oxidation of the 15-hydroxy group (blue) [ 8 ]


Anisocoria  caused by tropicamide instilled into the subject's right eye only.


Vitamin C biosynthesis in plants


Vitamin C supplements among other dietary supplements at a US drug store


The Nobel Prize winner  Linus Pauling  advocated taking vitamin C for the  common cold  in  a 1970 book .


Limes, lemons and oranges were among foods identified early as preventing or treating scurvy on long sailing voyages.


James Lind , a British Royal Navy surgeon who, in 1747, identified that a quality in fruit prevented scurvy in one of the first recorded  controlled experiments [ 166 ]


Albert Szent-Györgyi , pictured here in 1948, was awarded the 1937  Nobel Prize in Medicine  "for his discoveries in connection with the biological combustion processes, with special reference to vitamin   C and the catalysis of fumaric acid". [ 178 ]


Band keratopathy of a 60-year-old male


Eye specialist carrying out eye examination on a patient at a district hospital in Zambia


An Amsler grid, artist's conception, as it might be viewed by a person with  age related macular degeneration


Amsler grid, Chart 1


An Ishihara test image as seen by subjects with normal color vision and by those with a variety of color deficiencies


A Farnsworth–Munsell 100 Hue Test


A Farnsworth D-15 test


Anomaloscope using a Rayleigh Match


Schematic Electroretinography waves of healthy people.


An electroretinogram (ERG) test performed in 2014.


A historical photo of a patient undergoing an electroretinogram.


Age-related macular degeneration, a common eye condition among patients over the age of 65, can run in families.


Medical student giving eye exam at  ITESM-Campus Ciudad de México


Goldmann applanation tonometry (GAT) is a widely used method to measure intraocular pressure (IOP) at the slit lamp. The technique involves gently applanating the central cornea with a Goldmann applanation prism while the tear film is stained with fluorescein dye. Pressure is applied to the cornea until the inner edges of two semicircular fluorescein mires come into contact, forming a continuous circle. The corresponding reading on the tonometer scale represents the IOP of the measured eye.


Normal visual field of a right eye


Slit Lamp Examination


Fully dilated pupil prior to ophthalmoscopic examination to remove lens astigmatism (spasm of accommodation)


A view of the retina of the left eye under dilated fundoscopic examination, showing severe papilledema, possibly due to  intracranial hypertension


Using a  phoropter  to determine a prescription for eyeglasses


LEA symbols used in visual acuity test in individuals who do not read letters


Tile arrangement for the 100 hues test.


A physical set of tiles for the D15 hue color test.


Illuminant curves


Standardized curves for common display gamma settings.


Error by display


A typical scoring results screen from X-Rite's 100 Hues test evaluation software.


Colorblindness


4PRT Equipment


Figure 1 - Humphrey field analyser


Figure 2 - Chin Rest and Lens Holder


Figure 3 - Fixation targets  left:  central,  middle : small diamond,  right:   large diamond


Figure 4 - Analyser Printout  1: Reliability Indices  2: Numerical Display   3: Grey Scale  4: Total Deviation   5: Probability Display   6: Pattern Deviation   7: Global Indices   8: Glaucoma Hemifield Test   9: Visual Field Index


Figure 5 - Types of Visual Field Defects (right eye) A: Central scotoma B: Centrocaecal scotoma C: Nasal Step  D: Superior Arcuate  E: Nasal Wedge defect  F: Superior Nasal quadrantanopia  G: Superior Altitudinal  H: Nasal hemianopia  I: Enlarged Blind Spot with Paracentral scotoma located 15 degrees superiorly


Figure 6 - Artefacts (right eye)  A: Aphakia   B: Rim artefact   C: Chin slip  D: Lens position   E: Corneal opacity   F: Keratoconus   G: Ptosis   H: Pupil Miosis - 1mm  I: Pupil Miosis - 3mm


An example of one version of the LEA Symbols Test. In this picture, the test's four optotypes are displayed on a blanket to be used to diagnose the visual acuity of a young child.  Photo courtesy of Dr. Lea Hyvarinen & Lea-Test   http://www.lea-test.fi


Snellen chart


The Maddox Wing


The scale card of the Maddox Wing, depicting the horizontal, vertical, torsional scales and their respective arrows.


Equipment required to perform a Prism Fusion Range Test. From left to right: an accommodative fixation stick, a vertical prism bar, and a horizontal prism bar.


Diagram of the AOSLO setup


Schirmer test = 0,00 in Sjögren's syndrome


Variation of Snellen chart with another letter sequence. Australia, 1946


Labelled image of slit lamp:  On/off switch Illumination Joystick Handles for patient Alcohol swabs Eyepieces Forehead rest Chin rest Filter Changing Knob Slit beam length knob Slit beam width knob


This image is of the angle of the eye as seen through a slit lamp. It is labelled as Grade 3 according to Van Herick's grading system.


This image is of the angle of the eye as seen through a slit lamp. It is labelled as Grade 4 according to Van Herick's Grading system.


Goldmann Perimeter


Eye examination  with the aid of a slit lamp.


The Worth Four Light Test at a distance of 6 meters


Red Green Goggles used in the Worth Four Light Test


The Worth Four Light Test in dimmed lighting conditions


A brock string in use.


Negative  Hirschberg sign : the reflections form congruent points on both corneas.


A high-resolution spectral-domain OCT scan (3×3 mm) of a dry age-related macular degeneration eye showing geographic atrophy and drusen in macula on both cross-sectional and en face fly-through.


Optical coherence tomogram of a fingertip. It is possible to observe the sweat glands, having "corkscrew appearance"


Ocular OCT  retinal thickness map, right eye


Time-domain OCT of the macular area of a retina at 800 nm, axial resolution 3 μm


Spectral-domain OCT macula cross-section scan.


Fig. 1 Full-field OCT optical setup. Components include: super-luminescent diode (SLD), convex lens (L1), 50/50 beamsplitter (BS), camera objective (CO), CMOS-DSP camera (CAM), reference (REF), and sample (SMP). The camera functions as a two-dimensional detector array, and with the OCT technique facilitating scanning in depth, a non-invasive three-dimensional imaging device is achieved.


Fig. 2 Typical optical setup of single point OCT. Scanning the light beam on the sample enables non-invasive cross-sectional imaging up to 3 mm in depth with micrometer resolution.


Fig. 3 Spectral discrimination by swept-source OCT. Components include: swept source or tunable laser (SS), beamsplitter (BS), reference mirror (REF), sample (SMP), photodetector (PD), and digital signal processing (DSP)


Fig. 4 Spectral discrimination by Fourier-domain OCT. Components include: low coherence source (LCS), beamsplitter (BS), reference mirror (REF), sample (SMP), diffraction grating (DG) and full-field detector (CAM) acting as a spectrometer, and digital signal processing (DSP)


interference signals in TD vs. FD-OCT


Schematic view of a full-field OCT


Induced pluripotent stem cell  taken from blood cell and converted in  retinal pigment epithelium


(Top) 0.50 confirmation set; (Middle) trial lens box, including pinhole and occluder; (Bottom) Snellen chart


Trial frames fitted comfortably on the patient and occluder over left eye.


Step 1: Using the +/-0.50DS on the confirmation set to determine the initial best sphere correction.


Step 2: Presenting the 0.50JCC initially @ 90deg to determine any presence of astigmatism on that axis.


Step 3: The axis of the JCC must straddle the axis of the correcting cylinder in the trial frames, in both flip positions.


Step 4: The axis of the JCC must superimpose the axis of the correcting cylinder lens in the trial frames.


Step 5: Spherical lens power is altered and refined, if required.


"Do the letters stand out more on the red or green background?"


Duochrome is based on  chromatic aberration  of the eye.


The patient's subjective response to the duochrome test is a perfect indicator as to whether you have under-corrected, over-corrected, or adequately corrected their refractive error during the subjective refraction process.


Video-oculography examination in progress


A class at Nanjing No. 1 Experimental School performs eye exercises (2007).


Ampullae of Lorenzini, found in several basal groups of fishes, are jelly-filled canals connecting pores in the skin to sensory bulbs. They detect small differences in  electric potential  between their two ends.


How an ampulla of Lorenzini detects an electric field


Simplified Hot-wire sensor


Figure 2: Sectional view of lateral line in fish and its components


Earwig  with large cerci (top)


Cercus of an adult female  Gryllus pennsylvanicus


Diagram of the primary components of a chordotonal organ scolopidium


Forked tongue of a  carpet python  ( Morelia spilota mcdowelli )


Illustration from the 1855 paper of Christopher Johnston [ 1 ]


Oblique view of a  goldfish  ( Carassius auratus ), showing pored scales of the lateral line system


The lateral line system consists of canals that run along a fish's body, connecting rows of openings (pores) through the skin and scales to the water outside the body. Small sense organs, neuromasts (inset), are positioned both at intervals along the canals, and on the surface of the body. Each hair cell contains a bundle of sensory hairs.


A  three-spined stickleback  with stained neuromasts [ 10 ]


Lateral line rate coding indicates direction and sometimes strength of stimulus. One neuromast shown.


The motion detection system in fish works despite "noise" created by the fish itself. The brain copies the efferent commands it gives to the swimming muscles to the lateral line, effectively suppressing swimming noise and revealing small signals from the environment, such as from prey. [ 18 ]


The  electroreceptive  organs called  ampullae of Lorenzini  (red dots), illustrated here on the head of a  shark , evolved from the mechanosensory lateral line organs (gray lines) of the  last common ancestor  of vertebrates. [ 21 ] [ 22 ]


Tömösváry organ (arrow) on the head of a  symphylan , just behind the base of an antenna


The parietal  eye  (very small grey oval between the regular eyes) of a juvenile bullfrog ( Lithobates catesbeianus )


Adult  green anole  ( Anolis carolinensis ) clearly showing the parietal eye (small grey/clear oval) at the top of its head


Parietal eye of the Merrem's Madagascar swift ( Oplurus cyclurus ) is surrounded by a black-and-white spot on the skin, giving it the "three-eyed" appearance


Cochlea and vestibular system


Rhinophores  of  Aplysia californica .


The upper pair of  tentacles  on the head of the edible snail  Helix pomatia  have eyes, but the main sensory organs are sensory neurons for  olfaction  in the  epithelium  of the tentacles.


Eye pit of  Patella  sp.


Scheme of  pit eye .


Eye cup of  Pleurotomaria  sp.


Pinhole eye of  Haliotis  sp.


Closed eye of  Turbo coronatus .


Lens eye of  Bolinus brandaris .


Lens eye of  Nucella lapillus .


Scheme of  lens eye .


Eye of a snail.  1 - anterior chamber, 2 - lens,  3 - retina,  4 - optic nerve.


Drawing of cross section of the eye of  Helix pomatia .  1 -  lens  2 -  olfactory   epithelium  3 -  corneal epithelium  4 -  corneal endothelium  5 -  retina  6 - layer with  rod cells  7 -  fibrous connective tissue  layer  8 -  nerve  of the eye


Drawing of cross sections of the extracted tentacle (left) and constricted tentacle (right) with and eye of  Helix pomatia .  1 - nerve of an eye  2 -   3 -   4 - eye  5 - tentacle ganglion  6 -  epidermis  7 -   8 - nerve of an tentacle  9 - retractor muscle  10 -


Well-developed  lens  eye of  Eustrombus gigas  on  eyestalk  has a black  iris . There is a small  tentacle  on the eyestalk also.


Statocysts (ss) and statolith (sl) inside the head of  Gigantopelta chessoia .


Four trichobothria on the second leg of the spider  Paratropis tuxtlensis


Tympanal organ on the tibia of the katydid  Zabalius aridus


Tympanal organ of two species of moths, ventral view of abdomen ( Tineidae  and  Pyralidae )


The underside of a human tongue, showing its rich blood supply.


Foramen cecum and terminal sulcus labelled above


Features of the tongue surface


Lateral view of the tongue, with extrinsic muscles highlighted


Coronal section of tongue, showing intrinsic muscles


Blood supply of the tongue


Section through the human tongue; stained  H&E


Floor of pharynx at about 26 days showing lateral swellings at first pharyngeal arch (mandibular arch).


Giraffe's tongue


Extended proboscis of a long tongued  Macroglossum   moth


Removing skin from boiled beef tongue


Tongue and pancetta with  mâche


Russian  zakuski : cold cuts of tongue topped with mushrooms, cheese, nuts and prunes


Filipino dishes:  kare-kare , lengua with white sauce and  pancit  canton-bihon


Cold cut of blood tongue


Tremolo notation


A heterosexual couple French kissing


Sketch of an open mouth showing the frenulum and surrounding structures


Ankyloglossia


Horse sticking out its tongue


Horse tongue anatomy


A horse licking a  salt stone


Yawning


A horse sticks its tongue out to the side in discomfort


Snapping behavior


A horse tongue extended and held by a human hand.


Horse showing severe discomfort with this bit


Tongue tie of a racehorse at the Josselin racecourse, France, in 2019


Four stages of Khecarī mudrā. The tongue (red) is progressively stretched, and the  frenulum of the tongue  (not shown) sufficiently severed, over a period of months, until it can be turned back so as to reach inside the nasal cavity, and supposedly manipulate the flow of  bindu .


Khecari mudra is one of several mudras in traditional  Hatha yoga . [ 5 ] [ 6 ]


Lick granuloma  on a dog's paw


Filiform papilla, magnified.


Fungiform papillae, magnified and sectional diagram.


Magnified diagram of a vertical section through some foliate papillae in a rabbit.


Circumvallate papilla in vertical section, showing arrangement of the taste-buds and nerves


Tonsils and the throat–lingual tonsils labelled


Kali  sticking out her red tongue


The 50th anniversary tongue and lips logo


Mick Jagger wearing the tongue and lips logo t-shirt


Tongue cleaner


Tongue scraper


Tongue brush


A traditional ayurvedic tongue cleaner made of copper popularly used in Indian subcontinent.


Tongue depressor


The myth of the tongue map: that 1 tastes bitter, 2 tastes sour, 3 tastes salty, and 4 tastes sweet.


Piercing in progress


Straight barbells with either plastic or metal beads are commonly worn in tongue piercings.


Tongues usually swell for a short period of time after being pierced.


"Venom" piercings: two tongue piercings placed horizontally


Human vocal tract


Person with a tongue bifurcation body modification


A newspaper clipping from 1833, in which a tailor whose coat was stolen from a bowling alley advertises an offer to alter the coat to fit the thief


Kettledrum  double cross-beat. So-called because kettledrums were associated with  trumpets  and borrowed the terms for their rhythms from those for tonguing. [ 1 ]


Bones of the nose and septal cartilage


Roof of the mouth showing position of palatine bones making up the floor of the nose, and forming the  posterior nasal spine  for the attachment of the  musculus uvulae .


Nasal cartilages


Anatomy of the nasal cavity.  Nasal-associated lymphoid tissue  labelled NALT


Paranasal sinuses


Nose shapes used in  Topinard's  nasal index.


Carotid arteries


Multiple arteries supply blood to the nose; the nasal septum, shown here is supplied by the anterior and posterior ethmoidal arteries at top; the sphenopalantine artery at the back, and the anterior ethoidal artery and the superior labial artery over the cartilage. These arteries join at  Kiesselbach's plexus .


The  developing head  at about four weeks. The olfactory pit can be seen at the top.


Air enters the upper respiratory tract through the nose. The nasal conchae can be seen in this image.


The cells lining the nose involved in smell ( olfaction ) are shown here


Saddle nose  ( congenital syphilis )


Prosthetic nose  from 17th century Europe.


3D medical animation still shot depicting a human nose


The nose of a tapir


Elephants  have  prehensile  noses.


Person demonstrating the allergic salute.


An "aquiline" nasal profile


From parody nose classification  Notes on Noses : "It indicates great decision, considerable Energy, Firmness, Absence of Refinement, and disregard for the  bienseances  of life". [ 1 ]


A  CT scan  showing evidence of the nasal cycle: the more patent airway is on the right of the image, the swollen turbinates congesting the left


An electronic nose was tuned to the perceptual axis of odorant pleasantness, i.e., an axis ranging from very pleasant (e.g., rose) to very unpleasant (e.g., skunk). This allowed the eNose to then smell novel odorants it never encountered before, yet still generate odor pleasantness estimates in high agreement with human assessments regardless of the subject's cultural background. This suggests an innate component of odorant pleasantness that is tightly linked to molecular structure [ 1 ]


Electronic nose developed in Analytical Chemistry Department (Chemical Faculty of  Gdańsk University of Technology ) allows for rapid classification of food or environmental samples


Nasal hair


"Got your nose" hand position, with tip of thumb representing the stolen "nose." However, this "fig sign" may be interpreted as offensive or obscene in certain cultures.


A man with an exaggerated  "Jewish nose" depicted on the cover of an American joke book, 1908


A 1886 sketch by  Joseph Jacobs  that illustrates the degrees of "Jewishness" of a nose


A  Roman bust  incorrectly identified in the early 20th century as representing the Roman-Jewish historian and military leader  Josephus , based solely on stereotypes about the Jewish nose. Current scholarship definitively rejects this identification.


Two  shnorrers : a  Sephardi  and an  Ashkenazi  (1894)


American-Jewish singer and actress  Barbra Streisand  in a publicity photoshoot for  Hello, Dolly!  (1969)


Israeli-American musician and actress  Alana Haim


Coronal section of nasal cavity


18th century painting of Hokoji Temple by  Maruyama Ōkyo . Mimizuka can be seen in front of it (right)


Mimizuka from the front


Nasal bridge is the bony part of the nose, overlying the nasal bones, above the part in blue labeled "Cartilage of Septum".


The bridge is between the eyes, and just below them. The lower half of the nose is below the bridge.


Side view of the cartilages in the nose.


Right side view of the septal nasal cartilage.


Major alar and minor alar cartilages, seen from below.


External incision used during a rhinoplasty.


U.S. Air Force Maj. Brent Feldt, performing a septoplasty.


Patient with metal split after a rhinoplastic procedure.


Nasal cavity anatomy


CT scan  in the  coronal plane , showing the ostiomeatal complex (green area)


Clinical application of autologous NC-based cartilage tissues


Vomer  of infant


Spraying into a nostril while closing the opposite nostril to assure the dose


Notes on Noses , front-page picture


Jeorge Jabet, by  William Thomas Roden [ 3 ]


Nasothek displaying marble body parts once used to "repair" antique statuary.


Detail: A closer look at the Copenhagen Nasothek display shows wide variety in surface textures and style.


Display of plaster casts of noses at  Lund University


Nose prosthesis, ca. 1918


Turquoise gold nose ornament from the  Moche culture .


A Hindu bride wearing the Nath.


Nose-leaf diagram of a  horseshoe bat


Lateral view of the face with a saddle nose deformity far up on the bridge due to  granulomatosis with polyangiitis


Nasal sebum


George Cruikshank 's illustration of Slawkenbergius in  Tristram Shandy


Eye of a  European bison


Human eye , a refractive  cornea  type eye.


The eyes of a mantis shrimp (here  Odontodactylus scyllarus ) are considered the most complex in the whole animal kingdom.


A refractive cornea type eye of a human. The cornea is the clear domed part covering the  anterior chamber of the eye .


Eyelids  and  eyelashes  are a unique characteristic of most mammalian eyes, both of which are evolutionary features to protect the eye.


An image of a house fly compound eye surface by using  scanning electron microscope


Anatomy of the compound eye of an insect


Arthropods such as this  blue bottle fly  have compound eyes.


Evolution of the  mollusc eye


The eye of a  red-tailed hawk


1:posterior segment 2:ora serrata 3:ciliary muscle 4:ciliary zonules 5:Schlemm's canal 6:pupil 7:anterior chamber 8:cornea 9:iris 10:lens cortex 11:lens nucleus 12:ciliary process 13:conjunctiva 14:inferior oblique muscule 15:inferior rectus muscule 16:medial rectus muscle 17:retinal arteries and veins 18:optic disc 19:dura mater 20:central retinal artery 21:central retinal vein 22:optic nerve 23:vorticose vein 24:bulbar sheath 25:macula 26:fovea  27:sclera 28:choroid 29:superior rectus muscle 30:retina


Minimum (top) and maximum accommodation (bottom).


Two horse lenses suspended on water by cling wrap with four approximately parallel lasers directed through them. The 1   cm spaced grid indicates a near focus focal length of around 6   cm


The path of light through the eye calculated using four refractive indexes, cornea and lens curvatures approximating components of real eyes. Note objects in some size ranges and distances do not require the light path to bend noticeably to achieve focus.


Virtual eye showing the contribution to focus of different components.


Schachar model of lens focus


Tracing of Scheimpflug photographs of 20 year old human lens being thicker focusing near and thinner when focusing far. Internal layering of the lens is also significant


Wrinkled lens fibers in picture below compared to straight fibers above


Duane's classical curves showing the amplitude or width of accommodation as changing with age. Mean (B) and approximate lower (A) and upper (C) standard deviations are shown. [ 31 ]


Diving bird (Cormorant) lens focusing can be up to 80 dioptres for clearer underwater vision.


Bony fish eye. Note the harder more spherical lens than in land based animals and a none circular muscle to pull the lens backward


Light from a single point of a distant object and light from a single point of a near object being brought to a focus.


The pupil constricts when accommodation is initiated


Normalised absorption spectra of the three human photopsins and of human rhodopsin (dashed).


The pupillary light reflex is a quick but minor mechanism of adaptation


Visual Response to Darkness. Cones work at high light levels (during the day but also during driving at night in the headlamp spotlight). Rods take over at twilight and night. The y-axis has logarithmic scaling.


Reflection of camera flash from  tapetum lucidum


Extreme red light used on a ship's bridge at night to aid dark adaptation of the crew's eyes


Astronomer preserves night vision


Blackberry fruits


Schematic of the increment threshold curve of the rod system


Effect of night blindness. Left: good night vision. Right: nightblind.


Distribution of rods and cones along a line passing through the  fovea  and the blind spot of a human eye [ 1 ]


Night blind spot


Blinking


Birds, reptiles and sharks blink with a  nictitating membrane  from one side of the eye to the other.


Closed eye of a human, displaying  eyelashes  which function to catch irritants when the eye is blinked.


Bilateral cataracts in an infant due to  congenital rubella syndrome


Post traumatic rosette cataract of a 60-year-old male


Christmas tree cataract (diffuse illumination)


Cross-sectional view, showing the position of the human lens


Cataract surgery, using a temporal-approach phacoemulsification probe (in right hand) and "chopper" (in left hand) being done under operating microscope at the U.S. Navy Medical Center in Portsmouth, Virginia


Slit lamp  photo of posterior capsular opacification visible a few months after implantation of intraocular lens, seen on retroillumination


Slit lamp  photo of anterior capsular opacification visible a few months after implantation of intraocular lens, magnified view


A South African woman experiences newfound eyesight after a patch was removed after surgery to remove an eye cataract.


Disability-adjusted life years  for cataracts per 100,000 inhabitants in 2004: [ 67 ]              no data      <90      90–180      180–270      270–360      360–450      450–540          540–630      630–720      720–810      810–900      900–990      >990


Crew Building, Institute of Animal Genetics, King's Buildings, University of Edinburgh


Epigenetics Building, Institute of Animal Genetics, King's Buildings, University of Edinburgh


Schematic representation of the adult vertebrate (chick) lens (1b) and its formation during embryogenesis (1a I-III). From Bower et al., 1983 (Reference 17)


Compound eye of a  house centipede


Compound eye of a  dragonfly


Head of a  mantisfly  showing a compound eye


Drawing from  Robert Hooke 's  Micrographia  of the compound eye of a grey  drone fly


Compound eyes of a  paper wasp .


Fossilized compound eyes from the  Florissant Formation


Congenital cataract in an adult


Human eye


Bonobo  with dark  sclera


Gorilla  eyes


drawing of a  cone cell  showing the invaginations of the outer segment that form the 'discs'


Gaboon viper , its eye concealed by a disruptive mask


Early investigators  Abbott Handerson Thayer  and  Hugh Cott  noted that  active juvenile birds  like this  little ringed plover  chick have boldly disruptive patterns that camouflage the eye.


Cott used this diagram to illustrate "the inherent conspicuousness of an eye-spot", and hence to justify the need for a disruptive eye mask. [ 1 ]


The distribution of human photoreceptor cells shows how the photopic and scotopic systems exist in parallel, except in the fovea where the photopic system dominates.


Eye of a  golden eagle


Eye of a  bald eagle


Bald eagle


White-bellied sea eagle


Eyeball lengths: emmetropic, near-sighted (myopic) and far-sighted (hyperopic)


This image highlights the epicanthic folds in a person of  Mongol  descent.


Swedish ski racer  Jens Byggmark  with an epicanthic fold over his left eye.


The  Khoisan  and some other African groups have a high frequency of the epicanthic fold.


Major stages in the evolution of the eye in  vertebrates


The human eye, showing the  iris  and  pupil


The  stigma  (2) of the  euglena  hides a light-sensitive spot.


The  planarian  has "cup" eyespots that can slightly distinguish light direction.


The  nautilus  eye functions similarly to a  pinhole camera .


Light from a distant object and a near object being focused by changing the curvature of the  lens


Compound eye of  Antarctic krill


The irises of human eyes exhibit a wide spectrum of colours


A brown iris


A light brown iris with limbal ring


Amber eye


Hazel eye


Green eyes


A light blue iris with  limbal ring


Blue iris


Gray eye


Two different eye colors are known as  heterochromia iridum


Red-appearing albino eyes


A  Kayser–Fleischer ring  in a patient with  Wilson's disease


An example of complete heterochromia. The subject has one brown eye and one hazel eye.


An example of sectoral heterochromia. The subject has a blue iris with a brown section.


Light brown iris with a dark limbal ring


Transverse section of head of chick embryo of forty-eight hours’ incubation


Transverse section of head of chick embryo of fifty-two hours’ incubation, showing the lens and the optic cup


An example of eye movement over a photograph over the span of just two seconds.


Schematic demonstrating the actions and cranial nerve innervation (in subscript) of extraocular muscles.


Leonardo da Vinci: The eye has a central line and everything that reaches the eye through this central line can be seen distinctly.


Horizontal eye movement in reading. Left-to-right movement may be seen as "upstairs", and right-to-left saccades are clear.


A diagram demonstrating the  acuity  of foveal vision in reading


A Parisian street scene painted by  Jean Béraud .  A fashionable beauty reads the posters on the kiosk while two gentlemen surreptitiously ogle her.


Yellow-naped amazon  parrot eye pinning.


An airman using a welding mask. Failing to use proper eye protection when welding may lead to blindness.


Examples of different styles of safety glasses


Cover style safety Goggles


Empiral Vision Grey Goggle


Speedglas welding helmet.


Sand Blasting in protective hood


An  Electrician's Mate  wearing a face shield while checking for bad fuses.


Full face shield respirator


Blood vessels of the eyelids, front view


Eyelashes grow from the eyelid margin and project outwards and curl away from the eye, to protect the eye from foreign objects


Eyelid affected by  stye


A South Korean woman, before (left) and after (right) undergoing  double eyelid surgery . Note the presence of the  epicanthic fold  in both photographs.


Eyelid skin pushing the central and inner upper  eyelashes  downwards into this person's field of vision, exacerbated by the excess length and thickness of their eyelashes. Note that the lashes in the outer portion of the eyelid are not pushed by the eyelid and curl upwards.


Pulmonate   land snails  usually have two sets of  tentacles  on their head: the upper pair have an eye at the end; the lower pair are for  olfaction . [ 1 ]


Microsaccades and Ocular Drifts


The lines on this image display the saccadic and microsaccadic movements of a person's eye while they looked at this face. The involuntary, micro-saccadic movement is not steady when the person's eyes are concentrated at the eyes of the woman, while the voluntary, saccadic movement goes around the periphery of the face once at any give point.


Brownian Motion


Ocular microtremor tracing with burst sections underlined


Parafoveal magnification paradigm: Graphical depiction of the parafoveal magnification paradigm (Miellet et al., 2009).  The location of each fixation is indicated with an arrow and the corresponding display for that fixation is represented.  Consecutive lines represent the chronological order of fixations.


Mach bands = visual illusion of brightness (intensive property)


Illusions of position (Poggendorff), orientation (Zöllner) and, below, length (Müller-Lyer)


Hering Illusion of curvature


Delboeuf Illusion of size: left inner circle and right outer circle are actually equal


Vertical–horizontal illusion


Shifted-chessboard illusion