January 24th
2010

Eye Anatomy  ⁄  Retina, Macula, Fovea, Foveola

As I told you, the Dynamic Fixation Method contains three difficulty levels. Last year we finished level one for beginners. Now we start intermediate study with level two. I will tell you various techniques for better eyesight. But first, here is some information about eye anatomy for understanding the visual techniques.

The retina is the inner layer of the eyeball, located between the choroid and the vitreous membrane. The retina contains photoreceptor cells, the rods and cones that transform light energy into a neural signal. Rods are more active in dim illumination, and cones are active in well-lit conditions.

Rods are extremely sensitive in poorly-lit conditions (scotopic vision), when cones are least responsive. In scotopic vision, the light-sensitive retina allows detection of objects at low levels of illumination. Its ability to recognize fine detail is poor, however, and color vision is absent; objects are seen in shades of gray.

Cone activity dominates in photopic vision, when the retina is responsive to a broader range of light wavelengths. Bright illumination is necessary for the sharp visual acuity and color discrimination of photopic vision. Cones are designated, depending on the wave-length that they absorb, as red (588nm), green (531nm), or blue (420nm).


cones_rod

The retina includes the macula, the area at the posterior pole, which is used for sharpest acuity and color vision. The term macula refers to the area of darker coloration that is approximately the same size as the optic disc. This is the retina as seen through an ophthalmoscope.

retina_macula_disc4

The retina is often described as consisting of two regions, central and peripheral. The central area is specialized for visual acuity, and the peripheral retina is designated for detecting large objects and motion. The central retina is rich in cones, and in the peripheral retina the rods dominate. This diagram shows rod and cone densities along the horizontal meridian.

rods_cones

The macula lutea is approximately 5.5mm in diameter; its center is approximately 3.5mm lateral to the edge of the optic disc and approximately 1mm inferior to the center of the optic disc. The shallow depression in the center of the macula is the fovea. This depression is formed because the retinal cells are displaced, leaving only photoreceptors in the center. The fovea has a horizontal diameter of approximately 1.5mm. The fovea has the highest concentration of cones in the retina; estimates vary from 199 000 to 300 000 cones per square millimeter. The curved wall of the depression gradually slopes to the floor, the foveola. The diameter of the foveola is approximately 0.35mm. The annular zone surrounding the fovea can be divided into an inner parafoveal area and an outer perifoveal area. The width of the parafoveal area is 0.5mm and of the perifoveal area is 1.5mm.

central_retina2

Love… respect… care…

Dr. Arkadiy Davydov

11 Responses

  1. Fiona McKechnie:

    06.12.2010 at 22:13 #

    hello Dr

    I read your article with interest.
    I am female, 45 and as far as I know was born with a ‘lazy eye’. My left eye has very poor visual acuity, with good peripheral vision. My right eye has perfect vision. What is this and what caused it? Is there anything that can be done?

    with regards Fiona

  2. Doc:

    10.12.2010 at 10:34 #

    Fiona, you should read my articles Myopia and Binocular Vision Development, parts 1-2-3-4. Generally speaking, the treatment of lazy eye should be started with easy exercises when infants begin to follow moving objects with their eyes at around three months of age. I named this program ‘the vaccination against weak eyesight’. I’ll try to upload some videos with similar exercises soon.

  3. Agnieszka Kubicka-Trząska:

    10.05.2011 at 11:51 #

    Dear Doctor
    I am an ophthalmologist. I have read your interesting article about the prevention of myopia. I am working on my MD thesis about the AMD. I am interested in one of your pictures I found in your article -The anatomy of the macula. I would appreciate if you are so kind and give me a permission to copy it.
    Sincerely yours
    Agnieszka Kubicka-Trząska

  4. Doc:

    10.05.2011 at 23:06 #

    Dear Agnieszka,
    of course you can use any picture from my blog for your MD.
    Good luck!

  5. Thought exercise regarding number of RPE cells injected, rats vs. humans:

    19.05.2011 at 02:59 #

    […] Country:

    I love thought experiments!

    The macula is about 5.5mm in diameter Retina, macula, fovea, foveola | ForBestVision.com
    The radius of the macula is 2.75 mm
    The area of the macula is 23.7 square mm.

    If 200 k cells cover 34.64 square mm, then the entire macular area could be covered by this dose to one layer, plus some left over.

    If the entire macula is not yet damaged, then fewer cells would do the job in one layer, or same number of cells for several layers.

    Looks pretty good for seeing some possible visual improvement even with initial 50k cell dose.

    My brain feels stronger already! […]

  6. mike:

    16.08.2011 at 02:01 #

    I’ve had a Toric lens and lasik almost 2 years ago in my right eye. My mid and distant vision were okay but over the last 6 months it is more blurred. I was told that my fovea has flattened out. This right eye is my main vision eye as I had amblyopia as a child and the vision in my left eye has never been good and I suppress vision there. Is there anything that I can do to correct the fovea problem or would it be to dangerous with this being my main vision eye?

  7. Doc:

    16.08.2011 at 09:39 #

    mike, have you been seen by retinal specialists? What was the cause that your fovea has flattened out?

  8. liluam patricia revheim:

    16.06.2013 at 23:01 #

    Dear Doctor.
    For the last 18 months in my life (I am 55) I have suffered a loss of vision on my left eye. It started when I took on video-editting trips aboard, spending 48 to 72 hours in front of a PC. I kept a week break in between videos, about 50 of them, but the last 2 were 72 hours work and I only kept 3 days apart… My eyes cried day and night for a month, then daytime for a year, when I went to seek medical help. I have not been diagnosed, but DMV has given me 48 days to get driving glasses, I had 2 that didn’t pass, before I didn’t need glasses…My Eye-doctor has told me they can’t help my eye (the left eye is worse than the right eye, I got 6.75 S x 3.75 D prescription but the left eye couldn’t do the distance reading. I read and write without any aid. How can I improve my prescription in order to pass the DMV test?

  9. Doc:

    19.06.2013 at 22:54 #

    Patricia, unfortunately I have no ideas how you can improve your prescription in order to pass the DMV test.

  10. Willie:

    06.11.2013 at 09:55 #

    Hi Doc
    I have been wearing glasses for quit some time now but lately my eyes are getting worse. I’m a 70 year old minister and om the computer all day sometimes and the print has gone from 12pts(times Romans)font to a 24 (arial)font. I also put some honey, and vinegar drops in my eye. I thought it was helping but all of a sudden vision started getting worse.

    I have been diagnosed with type 2 diabetes and have had a stroke that affect my eyes. I’m also on several medications for diabetes, high-blood and cholesterol. I am taking the following medication daily:
    *Metforman, doses taken over a period of time 1000 MG, 850 MG, 400 MG (Was taking , but not currently taking)
    *mettoprolol 50 MG,
    *glipizide 10 MG
    *clonidine 0.1MG,
    *lisinopril 40 MG,
    *B12-1000mg,
    *hyrochlorothiazide 25 MG,
    * Pioglitazone 45 MG
    * Simuastatin 40 MG
    *Cyanocobalamin 1000 MCG (Once A Month)

    Please advise.

  11. Doc:

    07.11.2013 at 12:32 #

    Willie, probably it’s cataracts or age-related macular degeneration (AMD). Please visit your ophthalmologist.

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