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Simple Anatomy of the Retina by Helga Kolb

Helga Kolb

1. Overview.

When an ophthalmologist uses an ophthalmoscope to look into your eye he sees the following view of the retina (Fig. 1).

In the center of the retina is the optic nerve, a circular to oval white area measuring about 2 x 1.5 mm across. From the center of the optic nerve radiates the major blood vessels of the retina. Approximately 17 degrees (4.5-5 mm), or two and half disc diameters to the left of the disc, can be seen the slightly oval-shaped, blood vessel-free reddish spot, the fovea, which is at the center of the area known as the macula by ophthalmologists.

Fig. 1. Retina as seen through an opthalmoscope

 

CLICK HERE to see an animation (from the iris to the retina) (Quicktime movie)

A circular field of approximately 6 mm around the fovea is considered the central retina while beyond this is peripheral retina stretching to the ora serrata, 21 mm from the center of the retina (fovea). The total retina is a circular disc of between 30 and  40 mm in diameter (Polyak, 1941; Van Buren, 1963; Kolb, 1991).

Fig. 1.1. A schematic section through the human eye with a schematic enlargement of the retina

The retina is approximately 0.5 mm thick and lines the back of the eye. The optic nerve contains the ganglion cell axons running to the brain and, additionally, incoming blood vessels that open into the retina to vascularize the retinal layers and neurons (Fig. 1.1). A radial section of a portion of the retina reveals that the ganglion cells (the output neurons of the retina) lie innermost in the retina closest to the lens and front of the eye, and the photosensors (the rods and cones) lie outermost in the retina against the pigment epithelium and choroid. Light must, therefore, travel through the thickness of the retina before striking and activating the rods and cones (Fig. 1.1). Subsequently the absorbtion of photons by the visual pigment of the photoreceptors is translated into first a biochemical message and then an electrical message that can stimulate all the succeeding neurons of the retina. The retinal message concerning the photic input and some preliminary organization of the visual image into several forms of sensation are transmitted to the brain from the spiking discharge pattern of the ganglion cells.

A simplistic wiring diagram of the retina emphasizes only the sensory photoreceptors and the ganglion cells with a few interneurons connecting the two cell types such as seen in Figure 2.

Fig. 2. Simple organization of the retina

When an anatomist takes a vertical section of the retina and processes it for microscopic examination it becomes obvious that the retina is much more complex and contains many more nerve cell types than the simplistic scheme (above) had indicated. It is immediately obvious that there are many interneurons packed into the central part of the section of retina intervening between the photoreceptors and the ganglion cells (Fig 3).

All vertebrate retinas are composed of three layers of nerve cell bodies and two layers of synapses (Fig. 4). The outer nuclear layer contains cell bodies of the rods and cones, the inner nuclear layer contains cell bodies of the bipolar, horizontal and amacrine cells and the ganglion cell layer contains cell bodies of ganglion cells and displaced amacrine cells. Dividing these nerve cell layers are two neuropils where synaptic contacts occur (Fig. 4).

 

The first area of neuropil is the outer plexiform layer (OPL) where connections between rod and cones, and vertically running bipolar cells and horizontally oriented horizontal cells occur (Figs. 5 and 6).

 

Fig. 5. 3-D block of retina with OPL highlighted
Fig. 6. Light micrograph of a vertical section through the OPL

 

The second neuropil of the retina, is the inner plexiform layer (IPL), and it functions as a relay station for the vertical-information-carrying nerve cells, the bipolar cells, to connect to ganglion cells (Figs. 7 and 8). In addition, different varieties of horizontally- and vertically-directed amacrine cells, somehow interact in further networks to influence and integrate the ganglion cell signals. It is at the culmination of all this neural processing in the inner plexiform layer that the message concerning the visual image is transmitted to the brain along the optic nerve.

Fig. 7. 3-D block of retina with IPL highlighted
Fig. 8. Light micrograph of a vertical section through the OPL

 

2. Central and peripheral retina compared.

Central retina close to the fovea is considerably thicker than peripheral retina (compare Figs. 9 and 10). This is due to the increased packing density of photoreceptors, particularly the cones, and their associated bipolar and ganglion cells in central retina compared with peripheral retina.

 

Fig. 9. Light micrograph of a vertical section through human central retina
Fig. 10. Light micrograph of a vertical section through human peripheral retina
  • Central retina is cone-dominated retina whereas peripheral retina is rod-dominated. Thus in central retina the cones are closely spaced and the rods fewer in number between the cones (Figs. 9 and 10).
  • The outer nuclear layer (ONL), composed of the cell bodies of the rods and cones is about the same thickness in central and peripheral retina. However in the peripheral the rod cell bodies outnumber the cone cell bodies while the reverse is true for central retina. In central retina, the cones have oblique axons displacing their cell bodies from their synaptic pedicles in the outer plexiform layer (OPL). These oblique axons with accompanying Muller cell processes form a pale-staining fibrous-looking area known as the Henle fibre layer. The latter layer is absent in peripheral retina.
  • The inner nuclear layer (INL) is thicker in the central area of the retina compared with peripheral retina, due to a greater density of cone-connecting second-order neurons (cone bipolar cells) and smaller-field and more closely-spaced horizontal cells and amacrine cells concerned with the cone pathways (Fig. 9). As we shall see later, cone-connected circuits of neurons are less convergent in that fewer cones impinge on second order neurons, than rods do in rod-connected pathways.
  • A remarkable difference between central and peripheral retina can be seen in the relative thicknesses of the inner plexiform layers (IPL), ganglion cell layers (GCL) and nerve fibre layer (NFL) (Figs. 9 and 10). This is again due to the greater numbers and increased packing-density of ganglion cells needed for the cone pathways in the cone-dominant foveal retina as compared the rod-dominant peripheral retina. The greater number of ganglion cells means more synaptic interaction in a thicker IPL and greater numbers of ganglion cell axons coursing to the optic nerve in the nerve fibre layer (Fig. 9).

 

3. Muller glial cells.

Fig. 11. Vertical view of Golgi stained Muller glial cells

Muller cells are the radial glial cells of the retina (Fig. 11). The outer limiting membrane (OLM) of the retina is formed from adherens junctions between Muller cells and photoreceptor cell inner segments. The inner limiting membrane (ILM) of the retina is likewise composed of laterally contacting Muller cell end feet and associated basement membrane constituents.

The OLM forms a barrier between the subretinal space, into which the inner and outer segments of the photoreceptors project to be in close association with the pigment epithelial layer behind the retina, and the neural retina proper. The ILM is the inner surface of the retina bordering the vitreous humor and thereby forming a diffusion barrier between neural retina and vitreous humor (Fig. 11).

Throughout the retina the major blood vessels of the retinal vasculature supply the capillaries that run into the neural tissue. Capillaries are found running through all parts of the retina from the nerve fibre layer to the outer plexiform layer and even occasionally as high as in the outer nuclear layer. Nutrients from the vasculature of the choriocapillaris (cc) behind the pigment epithelium layer supply the delicate photoreceptor layer.

 

4. Foveal structure.

The center of the fovea is known as the foveal pit (Polyak, 1941) and is a highly specialized region of the retina different again from central and peripheral retina we have considered so far. Radial sections of this small circular region of retina measuring less than a quarter of a millimeter (200 microns) across is shown below for human (Fig. 12a) and for monkey (Fig.12b).

 

Fig. 12a. Vertical section of the human fovea from Yamada (1969)
Fig. 12b. Vertical section of the monkey fovea from Hageman and Johnson (1991)

The fovea lies in the middle of the macula area of the retina to the temporal side of the optic nerve head (Fig. 13a, A, B). It is an area where cone photoreceptors are concentrated at maximum density, with exclusion of the rods, and arranged at their most efficient packing density which is in a hexagonal mosaic. This is more clearly seen in a tangential section through the foveal cone inner segments (Fig. 13b).

OCTmacula

Fig 13a. A) fundus photo of a normal human macula, optic nerve and blood vessels around the fovea. B) Optical coherence tomography (OCT) images of the same normal macular in the area that is boxed in green above (A). The foveal pit (arrow) and the sloping foveal walls with dispelled inner retina neurons (green and red cells) are clearly seen.  Blue cells are the packed photoreceptors, primarily cones, above the foveal center (pit).

Fig. 13. Tangential section through the human fovea

 

Below this central 200 micron diameter central foveal pit, the other layers of the retina are displaced concentrically leaving only the thinnest sheet of retina consisting of the cone cells and some of their cell bodies (right and left sides of Figs. 12a and 12b). This is particularly well seen in optical coherence tomography (OCT) images of the living eye and retina (Fig. 13a, B).  Radially distorted but complete layering of the retina then appears gradually along the foveal slope until the rim of the fovea is made up of the displaced second- and third-order neurons related to the central cones. Here the ganglion cells are piled into six layers so making this area, called the foveal rim or parafovea (Polyak, 1941), the thickest portion of the entire retina.

 

5. Macula lutea.

The whole foveal area including foveal pit, foveal slope, parafovea and perifovea is considered the macula of the human eye. Familiar to ophthalmologists is a yellow pigmentation to the macular area known as the macula lutea (Fig. 14).

This pigmentation is the reflection from yellow screening pigments, the xanthophyll carotenoids zeaxanthin and lutein (Balashov and Bernstein, 1998), present in the cone axons of the Henle fibre layer. The macula lutea is thought to act as a short wavelength filter, additional to that provided by the lens (Rodieck, 1973). As the fovea is the most essential part of the retina for human vision, protective mechanisms for avoiding bright light and especially ultraviolet irradiation damage are essential. For, if the delicate cones of our fovea are destroyed we become blind.

Fig. 14. Ophthalmoscopic appearance of the retina to show macula lutea

 

Fig. 15. Vertical section through the monkey fovea to show the distribution of the macula lutea. From Snodderly et al., 1984

The yellow pigment that forms the macula lutea in the fovea can be clearly demonstrated by viewing a section of the fovea in the microscope with blue light (Fig. 15). The dark pattern in the foveal pit extending out to the edge of the foveal slope is caused by the macular pigment distribution (Snodderly et al., 1984).

 

Fig. 16. Appearance of the cone mosaic in the fovea with and without macula lutea

If one were to visualize the foveal photoreceptor mosaic as though the visual pigments in the individual cones were not bleached, one would see the picture shown in Figure 16 (lower frame) (picture from Lall and Cone, 1996). The short-wavelength sensitive cones on the foveal slope look pale yellow green, the middle wavelength cones, pink and the long wavelength sensitive cones, purple. If we now add the effect of the yellow screening pigment of the macula lutea we see the appearance of the cone mosaic in Figure 16 (upper frame). The macula lutea helps enhance achromatic resolution of the foveal cones and blocks out harmful UV light irradiation (Fig. 16 from Abner Lall and Richard Cone, unpublished data).

 

6. Ganglion cell fiber layer.

The ganglion cell axons run in the nerve fiber layer above the inner limiting membrane towards the optic nerve head in a arcuate form (Fig. 00, streaming pink fibers).  The fovea is, of course, free of a nerve fiber layer as the inner retina and ganglion cells are pushed away to the foveal slope.  The central ganglion cell fibers run around the foveal slope and sweep in the direction of the optic nerve.  Peripheral ganglion cell axons continue this arcing course to the optic nerve with a dorso/ventral split along the horizontal meridian (Fig. 00).  Retinal topography is maintained in the optic nerve, through the lateral geniculate to the visual cortex.

Fig. 00.  Schematic representation of the course of ganglion cell axons in the retina.  The retinotopic origin of these nerve fibers is respected throughout the visual pathway.  (Modified from Harrington DO, Drake MV.  The visual fields.  6th ed. St. Louis: CV Mosby; 1990, with permission)

 

 

7. Blood supply to the retina.

There are two sources of blood supply to the mammalian retina: the central retinal artery and the choroidal blood vessels. The choroid receives the greatest blood flow (65-85%) (Henkind et al., 1979) and is vital for the maintainance of the outer retina (particularly the photoreceptors) and the remaining 20-30% flows to the retina through the central retinal artery from the optic nerve head to nourish the inner retinal layers. The central retinal artery has 4 main branches in the human retina (Fig. 17).

Fig. 17. Fundus photograph showing flourescein imaging of the major arteries and veins in a normal human right eye retina. The vessels emerge from the optic nerve head and run in a radial fashion curving towards and around the fovea (asterisk in photograph) (Image courtesy of Isabel Pinilla, Spain)

The arterial intraretinal branches then supply three layers of capillary networks i.e. 1) the radial peripapillary capillaries (RPCs) and 2) an inner and 3) an outer layer of capillaries (Fig. 18a). The precapillary venules drain into venules and through the corresponding venous system to the central retinal vein (Fig. 18b).

 

Fig. 18a. Flatmount view of a rat retina stained with NADPH-diaphorase at the level of focus of a major artery and arterioles. (Courtesy of Toby Holmes, Moran Eye Center)
Fig. 18b. Flatmount view of a rat retina stained with NADPH-diaphorase at the level of focus of a major vein and venules. (Courtesy of Toby Holmes, Moran Eye Center)

The radial peripapillary capillaries (RPCs) are the most superfical layer of capillaries lying in the inner part of the nerve fiber layer, and run along the paths of the major superotemporal and inferotemporal vessels 4-5 mm from the optic disk (Zhang, 1994). The RPCs anatomose with each other and the deeper capillaries. The inner capillaries lie in the ganglion cell layers under and parallel to the RPCs. The outer capillary network runs from the inner plexiform layer to the outer plexiform layer thought the inner nuclear layer (Zhang, 1974).

As will be noticed from the flourescein angiography of Figure 17, there as a ring of blood vessels in the macular area around a blood vessel- and capillary-free zone 450-600 um in diameter, denoting the fovea. The macular vessels arise from branches of the superior temporal and inferotemporal arteries. At the border of the avascular zone the capillaries become two layered and finally join as a single layered ring. The collecting venules are more deep (posterior) to the arterioles and drain blood flow back into the main veins (Fig. 19, from Zhang, 1974). In the rhesus monkey this perimacular ring and blood vessel free fovea is clearly seen in the beautiful drawings made by Max Snodderly’s group (Fig. 20, Sodderly et al., 1992.)

 

Fig. 19. The macular vessels of the monkey eye form a ring around the avascular fovea (star)(From Zhang, 1994)
Fig. 20. Diagram of the retinal vasculature around the fovea in the rhesus monkey derived from more than 80 microscope fields. (From Snodderly et al., 1992)

The choroidal arteries arise from long and short posterior ciliary arteries and branches of Zinn’s circle (around the optic disc). Each of the posterior ciliary arteries break up into fan-shaped lobules of capillaries that supply localized regions of the choroid (Hayreh, 1975). The macular area of the choroidal vessels are not specialized like the retinal blood supply is (Zhang, 1994). The arteries pierce the sclera around the optic nerve and fan out to form the three vascular layers in the choroid: outer (most scleral), medial and inner (nearest Bruchs membrane of the pigment epithelium) layers of blood vessels. This is clearly shown in the corrosion cast of a cut face of the human choroid in Figure 21a (Zhang, 1974). The corresponding venous lobules drain into the venules and veins that run anterior towards the equator of the eyeball to enter the vortex veins (Fig. 21b). One or two vortex veins drain each of the 4 quadrants of the eyeball. The vortex veins penetrate the sclera and merge into the ophthalmic vein as shown in the corrosion cast of Figure 21b (Zhang. 1994).

 

Fig. 21a. The three vascular layers in the choroid: outer arteries and veins(red/blue arrow), medial arterioles and venules(red arrow) and inner capillary bed (yellow star. Corrosion cast of a cut face of the human choroid (From Zhang, 1994)
Fig. 21b. Corrosion cast of the upper back of the human eye with the sclera removed. The vortex veins collect the blood from the equator of the eye and merge with the ophthalmic vein. (From Zhang, 1994).

 

8. Degenerative diseases of the human retina.

The human retina is a delicate organization of neurons, glia and nourishing blood vessels. In some eye diseases, the retina becomes damaged or compromised, and degenerative changes set in that eventally lead to serious damage to the nerve cells that carry the vital mesages about the visual image to the brain. We indicate four different conditions where the retina is diseased and blindness may be the end result. Much more information concerning pathology of the whole eye and retina can be found in a website made by eye pathologist Dr. Nick Mamalis, Moran Eye Center.

 

Fig. 22. A view of the fundus of the eye and of the retina in a patient who has age-related macular degeneration.
Fig. 23. A view of the fundus of the eye and of the retina in a patient who has advanced glaucoma.

Age related macular degeneration is a common retinal problem of the aging eye and a leading cause of blindness in the world. The macular area and fovea become compromised due to the pigment epithelium behind the retina degenerating and forming drusen (white spots, Fig. 22) and allowing leakage of fluid behind the fovea. The cones of the fovea die causing central visual loss so we cannot read or see fine detail.

Glaucoma (Fig. 23) is also a common problem in aging, where the pressure within the eye becomes elevated. The pressure rises because the anterior chamber of the eye cannot exchange fluid properly by the normal aqueous outflow methods. The pressure within the vitreous chamber rises and compromises the blood vessels of the optic nerve head and eventually the axons of the ganglion cells so that these vital cells die. Treatment to reduce the intraocular pressure is essential in glaucoma.

 

Fig. 24. A view of the fundus of the eye and of the retina in a patient who has retinitis pigmentosa
Fig. 25. A view of the fundus of the eye and of the retina in a patient who has advanced diabetic retinopathy

Retinits pigmentosa (Fig. 24) is a nasty hereditary disease of the retina for which there is no cure at present. It comes in many forms and consists of large numbers of genetic mutations presently being analysed. Most of the faulty genes that have been discoverd concern the rod photoreceptors. The rods of the peripheral retina begin to degenerate in early stages of the disease. Patients become night blind gradually as more and more of the peripheral retina (where the rods reside) becomes damaged. Eventally patients are reduced to tunnel vision with only the fovea spared the disease process. Characteristic pathology is the occurence of black pigment in the peripheral retina and thinned blood vessels at the optic nerve head (Fig. 24).

Diabetic retinopathy is a side effect of diabetes that affects the retina and can cause blindness (Fig. 25). The vital nourishing blood vessels of the eye become compromised, distorted and multiply in uncontrollable ways. Laser treatment for stopping blood vessel proliferation and leakage of fluid into the retina, is the commonest treatment at present.

 

9. References.

 

Balashov NA, Bernstein PS. Purification and identification of the components of the human macular carotenoid metabolism pathways. Invest Ophthal Vis Sci.1998;39:s38.

Hageman GS, Johnson LV. The photoreceptor-retinal pigmented epithelium interface. In: Heckenlively JR, Arden GB, editors. Principles and practice of clinical electrophysiology of vision. St. Louis: Mosby Year Book; 1991. p. 53-68.

Harrington, D.O. and Drake, M.V. (1990) The Visual Fields, 6th ed. Mosby. St. Louis.

Hayreh SS. Segmental nature of the choroidal vasculature. Br J Ophthal. 1975;59:631–648. [PubMed] [Free Full text in PMC]

Henkind P, Hansen RI, Szalay J. Ocular circulation. In: Records RE, editor. Physiology of the human eye and visual system. New York: Harper & Row; 1979. p. 98-155.

Kolb H. The neural organization of the human retina. In: Heckenlively JR, Arden GB, editors. Principles and practices of clinical electrophysiology of vision. St. Louis: Mosby Year Book Inc.; 1991. p. 25-52.

Polyak SL. The retina. Chicago: University of Chicago Press; 1941.

Rodieck RW. The vertebrate retina: principles of structure and function. San Francisco: W.H. Freeman and Company; 1973.

Snodderly DM, Auran JD, Delori FC. The macular pigment. II. Spatial distribution in primate retina. Invest Ophthal Vis Sci. 1984;25:674–685. [PubMed]

Snodderly DM, Weinhaus RS, Choi JC. Neural-vascular relationships in central retina of Macaque monkeys (Macaca fascicularis). J Neurosci. 1992;12:1169–1193.[PubMed]

Van Buren JM. The retinal ganglion cell layer. Springfield (IL): Charles C. Thomas; 1963.

Yamada E. Some structural features of the fovea centralis in the human retina. Arch Ophthal. 1969;82:151–159. [PubMed]

Zhang HR. Scanning electron-microscopic study of corrosion casts on retinal and choroidal angioarchitecture in man and animals. Prog Ret Eye Res. 1994;13:243–270.

 

 

 

Helga Kolb

Last Updated: October 8, 2011.

Comment Feed

83 Responses

  1. Bryan,
    This is a great resource – thank you for organizing it!
    I cound’t find a mention of the axonal map in the retina – something like in Figure 9.2 here:
    http://flylib.com/books/en/3.283.1.15/1/

    This is very helpful map because it illustrates the mechanism of arc scotomas after focal injury, and also arc phosphenes due to axonal stimulation by epiretinal implants…

    Cheers,

    Daniel

  2. chapter on retinal plasticity?

  3. I wonder if a commensurate OCT scan displayed next to some of the #D blocks/images would also be helpful?

  4. I found two things that I do not understand or are not correct. Thus, if I do not understand, please forgive me and try to answer me. If there is a mistake, well, this my little contribution to improve this wonderful website.
    1) In this chapter there is written that the retina is a circular disk of 42 mm diameter. In chapter “facts and figures concerning..” it is said that retina is 32 mm from ora to ora along the orizontal meridian. Which of the two measures is correct?
    2) In this chapter it is said that the peripheral retina stretches to the ora serrata, 21 mm from the center of the optic disk. However, as the optic disk is not central, the distance of the ora from the center of the optic disk should be less the 21 mm on the nasal side and more than 21 mm on the temporal side.

    EugenioJune 17, 2011 @ 4:31 amReply
    • Eugenio,

      These are general numbers as human eyes do come in different sizes, so should be considered to be estimates.

      As to your second point, technically you are correct. It should read from the center of the retina or the fovea.

  5. I have been diagnosed with retinal rings and wonder what my future holds? Can the condition be treated? what are my options?

    Garlan CunninghamJune 26, 2011 @ 8:06 amReply
    • Hey Garlan,

      First off, I have never heard of retinal rings… Don’t know what they are and could not find any information on that wording *anywhere*. If you could clarify this, perhaps I could point you in the right direction or find someone to answer your questions.

      Next up, if I did not say this, the lawyers would likely be barking down my shorts…. So, I should note that I am a research scientist and not a physician and that any information on Webvision should be considered as research appropriate and not be construed as clinically relevant, or medical advice. Information provided here is informational only. Medically related questions should be addressed with your health care providers.

  6. My wifes eye doctor said she has wrinkling of the retina.I have never heard of it.Cain’t find any info on it.

    Steve SpurgeonJuly 5, 2011 @ 7:47 pmReply
  7. Maybe but he said it was not detached. thanks

    Steve SpurgeonJuly 5, 2011 @ 8:11 pmReply
    • Get him to explain what that means and if you are still unsatisfied with that explanation, do not hesitate to get a second opinion. Don’t mess around with your eye health.

  8. My opthalmologist sees a suspicious round white area on the retina. She wants me to see a retinal specialist. What could this be?

    Margaret ParobyJuly 27, 2011 @ 1:27 pmReply
    • Hey Margaret,

      I cannot/will not say what your ophthalmologist might think the white spot is. Besides, Webvision is not really a forum for medical advice and all information and content here should not be construed as medical advice. I’d suggest talking with your physician and retinal specialist and making sure they clearly explain to you what they think is going on.

  9. been to many opthamoligist and none can tell me why some of the arties in my retina have closed/dried up, leaving me with blurred vision in right eye, any input?

    • Hard to say Angela, though this is not a forum for dispensation of medical advice. There can be many causes for vascular changes in the eye though. I’d suggest an ophthalmologist that specializes in vascular issues.

  10. is it possible to be presented with a high-resolution picture, ask the patient to describe the picture details, and from there, map out a retina map that describe which part of the rods/cones are not functioning?
    Thanks for any pointers.

  11. I had a eye check up for new glasses and they took a picture of my retina. The optometrist said he had never seen so much yellow matter behind the retina, which he said was dead cells and waste material behind my retina. He sent me to a eye surgery clinic. I cannot go because the cost right now is to high for me. Does anyone know if this is a serious condition. What it is called? Why I have this large amount of yellow color behind my retina.

    • Cheryl,

      Again. any information on Webvision should be considered as research appropriate and not be construed as clinically relevant, or medical advice. Information provided here is informational only. Medically related questions should be addressed with your health care providers.

      That said, there are many reasons why pigment in the back of the retina may differ from individual to individual and it is not necessarily a pathological finding. Though I would suggest that you find an ophthalmologist (not an optometrist) that can examine your eyes. In many cities there are low cost or free clinics that can give you an examination from an ophthalmologist and I would encourage you to find one.

  12. What does it mean if one is seeing flashes of lighting like picture out of the right eye when the head is turned to the right?

    • Hey Regina,

      First things first: information on Webvision should be considered as research appropriate and not be construed as clinically relevant, or medical advice. Information provided here is informational only. Medically related questions should be addressed with your health care providers.

      That said, there can be lots of causes for this from ocular migrane to detached retina to standard migrane. I’d advise you to consult with an ophthalmologist to work this through and get a proper diagnosis.

  13. Dear Doctor
    On examination my doctor says my retina in my left eye has become thin I dnt have proper vision in this eye What is the reason Can this mat be rectified to improve my vision

    V.NarayananNovember 27, 2011 @ 7:09 amReply
    • Standard disclaimer: information on Webvision should be considered as research appropriate and not be construed as clinically relevant, or medical advice. Information provided here is informational only. Medically related questions should be addressed with your health care providers.

      That said, there are many reasons why a retina may “thin” and a number of potential mechanisms. Get your physician to explain to you more precisely what is going on. Though, unfortunately, there are few clinical interventions for retinal degenerative processes, but the vision research community is tirelessly and aggressively looking into therapies and cures for vision loss.

  14. Dear Doctor,
    My Doctor says I am suuffering from the inflamation of the retina. OCT AND FFA WAS DONE. Now they suggest “OZURDEX” Injection which is very costly .Further the effect of the injection lasts only upto six months.My blood report is ok in every respect. pl. advise what care i should take to avoid injection. Iam 72 years old.——Reply

    karnalsingh bajajDecember 18, 2011 @ 11:45 pmReply
    • Dear Karnalsingh,

      We have a standard policy here on Webvision that I’ll reiterate again here: Standard disclaimer: information on Webvision should be considered as research appropriate and not be construed as clinically relevant, or medical advice. Information provided here is informational only. Medically related questions should be addressed with your health care providers.

      I am sorry that we cannot address any individual medical health care related question, but it is simply too difficult and inappropriate for us to address patient care concerns over the Internet. I do understand the costs of treatments and there may be some alternative ways of paying for them, but we cannot deal with any individual case here for practical and legal reasons.

  15. I have a question which is how many output cells are there in a standard human eye? I heard about an encoder which converts pixels to pulses that mimic what these output cells send to the brain via optic nerve. Neural networks(not biophysical kind) are good at taking input, adjusting equations to recognize patterns and then sending an output. How many inputs and how many outputs would you need to mimic the retinal output?

    Harry ListerJanuary 2, 2012 @ 12:13 amReply
    • Hey Harry,

      Not a simple question, but let me hazard a quick estimate of 70-80,000 ganglion cells per retina. Add to that about 14-16 output channels or classes of ganglion cells that project to a variety of locations in the brain and you have a difficult problem. You’d have to figure out how to encode every cell type…

      • Wow, are neuroscientists able to connect to the 14-16 output channels? I’d like to see that data.

        Harry ListerJanuary 2, 2012 @ 10:18 amReply
        • No… Currently we (retinal neuroscientists) do not know how the 14-16 output channels are encoded, though there are a number of laboratories that are doing high density recording of retinal ganglion cell outputs. This is an area of active investigation from a number of laboratories including Ning Tian, Alexander Sher and others.

          • Sheila Nirenburg of Cornell has apparently figured out the encoding and a transducer to send it. I found her short speech on it. They took the output and correlated it to the input images, as she said, mathematically generalized the code so it always applies. She says the transducer is the implant on the optic nerve and the encoder is worn as glasses. I’m interested in how the modulated pulses were correlated. I have a hunch how I would try to crack that. Thanks.

            Harry ListerJanuary 2, 2012 @ 5:50 pm
          • Yes, I am familiar with Dr. Nirenburg’s work and while impressive, my eyebrows are raised at some of the claims… That and she’s got some fundamental concepts of retinal degeneration wrong.

  16. Do you have any pictures of patients with FEVR (Familial Exudative Vitreo Retinopathy). My wife and daughter both have this condition. I have some images taken of my wife’s eyes, at Riley Hospital. However, I do not have the expertise to look at them and identify the various parts. Can you Help?

    • I do not have any imagery of FEVR, though the clinic may have some imagery. I will say however, that the anatomy of the eye should not change substantially. What will be different is varying levels of bleeding from the vessels of the eye. I’d suggest sitting down with your ophthalmologist and have him go over your particular imagery.

  17. Do you have a picture that maps two things onto a fundus image:

    1) the angle from fixation point (presumably fovea) at which an object appears on the retina. In other words, if I’m fixated centrally, where on the retina would I expect an object that is, say 5 degrees from that fixation point to be placed on the retina. I can imagine this as concentric rings like a topographical map.

    2) similarly, has anyone ever attempted to map visual acuity onto those concentric rings?

    Thanks!

    Rob HilkesJanuary 6, 2012 @ 2:57 pmReply
    • Rob,

      I do not currently have an image such as this, but I am absolutely certain that someone has generated it at some point. Unfortunately, I am traveling and on a very restricted bandwidth, otherwise I’d do some searching for you right now.

      Good luck.

  18. A query: There is a lot of mention of inner/outer plexiform layers and inner/outer nuclear layers of the retina.

    But where exactly is the border between the inner and outer retina that is also often mentioned in journal articles? One article states that the bipolar cells carry signals between inner and outer retina. But then, does that make the bipolar cells ‘middle retina’ or no-man’s land?

    I am having trouble seeing a morphological or landmark demarcating inner/outer retina. Can someone please clarify?

    Thanks

    Barbara Junghans

    Barbara JunghansJanuary 18, 2012 @ 3:44 amReply
  19. Hey Barbara,

    Good question. The inner retina is generally considered to be the inner nuclear layer on down to the fiber cell layer. Though the reality is that at some point in the middle of the outer plexiform layer the retina makes the transition as that is the connectivity layer between the photoreceptors and horizontal and bipolar cells.

  20. All
    What amazes me about the paper is the knowledge that blood flow is so important towards a healthy eye. This has apparently been known for years. A glaucoma patient like myself never knew for six years that there were means to measure blood flow until a few months ago. Meanwhile, lots of research ongoing about new eye drops to lower pressures in the eye. The better research in my mind would be to find ways to improve on blood flow with medications and injections, than to let a patient go to their visual demise with eye drops and ineffective SLT and trabecular surgeries. Twenty years after Dr. Alon Harris invented a way to measure blood flow, it is still not being pursued aggressively so that treatments could be used and tested by blood flow tests as to efficacy. Sad, sad indictment of the medical community.

    russell j. rutkeJanuary 30, 2012 @ 12:10 pmReply
  21. I suffer from POHS and I have lots of scarring. I have some distorted/grey areas on my Amsler Grid testing. These spots are very close, but not directly in my central vision. My retinal specialist doesn’t off much information – he’s extremely busy. When part of my vision is distorted (similar to macular degeneration), is this usually from choroidal neovascularization or just damage to the retina?

    • Dear Laura,

      We have a standard policy here on Webvision: information on Webvision should be considered as research appropriate and not be construed as clinically relevant, or medical advice. Information provided here is informational only. Medically related questions should be addressed with your health care providers.

      I am sorry that we cannot address any individual medical health care related question, but it is simply too difficult and inappropriate for us to address patient care concerns over the Internet. If you do not feel that your health care provider is delivering appropriate care, then I’d suggest shopping around for another ophthalmologist who specializes in retina. Also, make sure that you get the information from your health care provider that you are entitled to. Does not matter if he is busy. If he is not meeting your needs, then you should look for someone else.

  22. Can somebody explain to me the differences between a intraretinal haemorrhage and a subretinal one? Also where does exactly a flame shaped haemorrhage takes place in the retina and why does it take the shape of a flame?
    Thanks

    Luke GarrettMay 9, 2012 @ 2:22 pmReply
  23. People my age (around 55+) who were diagnosed myopic (nearsighted) in our pre-teens (usually around 10-11) seem to have never had normal distance eyesight, but we didn’t realize it until we got the lenses. However people younger than that, especially those in their 20’s, seem to remember having had clear distance eyesight which became uncontrollably blurry in middle or high school. Have any studies been done on this?

    John CookMay 22, 2012 @ 1:41 pmReply
  24. could you tell me more on the functions of all the layers of retina. and also the problems associated with these when they are destroyed.

  25. Numbering of the different chapters are wrong: number 7 is repeated and the name of number 6 is wrong:

    6. Blood supply to the retina.

    7. Blood supply to the retina.

    7. Degenerative diseases of the human retina.

    7. References.

    galimatiasSeptember 7, 2012 @ 10:43 amReply
  26. You have built a wonderful site. I would like some more information/resources on central serous choroidopathy. There’s not much out there, but I don’t know where to look, except google.

    Lauren HansonOctober 2, 2012 @ 6:55 pmReply
  27. Thank you for this interesting website. Who would I contact about using your nice opthalmoscope picture, and perhaps a few others?

    Abby Hafer
    Science Cepartment
    Curry College
    Milton, MA

    Abby HaferMarch 2, 2013 @ 2:27 pmReply
  28. Hello,

    Sorry, I am looking for some values for weeks and I cannot find anything clear. I appreciate it if you could help me.
    I am looking for the size of the nucleus for normal cell (eukaryote) and rod cell. I read that for normal cell the size of the nucleus is around 5-8 micrometer, but could not find anything about rod cell.
    Besides that, any information on the volume fraction of the chromatin inside the nucleus is really helpful. By volume fraction I mean the ratio of the volume of the chromatin in nucleus to the total volume of the nucleus.
    Thank you,
    Arash

    • Arash,

      Quickly looking at some TEM data, I am seeing mouse rod cell bodies at about 4-5 microns in diameter. The nucleus is around 1.5-3.3 microns depending upon extent of chromatin. The nucleolus is around 400-500nm. As to the volume ratio of chromatin, I have no numbers for that.

  29. There’s a broken link in section 8, near beginning, “a website made by eye pathologist Dr. Nick Mamalis, Moran Eye Center. Click here, ”

    Thanks to all for this excellent website.
    Regards,
    Bill

    Bill BarnsNovember 18, 2014 @ 8:27 pmReply



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Continuing the Discussion

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