February 23rd
2010

Eye Physiology  ⁄  Less Area of Active Vision Means Better Eyesight

Myopia or nearsightedness is a refractive defect of the eye. Those with myopia can see clearly at a close distance, but far away objects appear blurred.

There are two important questions related to nearsightedness,

“Why do nearsighted people try to see things close to their eyes?”

“Why do they have mental strain when gazing at an object?”

I am sure your answer in both cases is, “Because their far-distance eyesight is not sharp”. Yes, this is the most popular answer, but I do not accept it because of my empirical observations. I examined normal-sighted children with a habit of seeing close. Also they were gazing with mental strain. In preschool, they had 20/20 visual acuity, but subsequently in grade school, myopia developed as a consequence of wrong habits. Undoubtedly, the wrong visual behavior is the cause, and progression of myopia is the effect.


In this article, I will explain how my theory answers the pair of questions. But first there are a few mathematical calculations.

The normal eyeball is a sphere with a 24mm diameter. The formula to calculate circumference is C=πD, so the circumference of the normal eyeball is 3.14*24mm≈75mm. As you know, the  circumference includes 360 degrees. Let’s calculate angular sizes of some areas in the central retina.

Foveola 0.35mm*360°/75mm=1 2/3°=1° 40´

Fovea 1.5mm*360°/75mm=7 1/5°=7° 12´

Parafovea 0.5mm*360°/75mm=2 2/5°=2° 24´

Perifovea 1.5mm*360°/75mm=7 1/5°=7° 12´

central_retina_degrees

Thus, the area of the central retina is about 26°. The picture below shows the visual field of the right eye with areas of color vision. The area of blue color vision is the largest, and the area of green color vision is the smallest. The area of the central retina is demarcated in yellow. The grey area at the right side of the yellow circle is the blind spot (the projection of the optic disc). The purple dot in the center is the area of foveolar vision and the area inside the smallest black ring around the purple dot is approximately the area of foveal vision. The 1-2º large area of foveolar vision is about the size of a thumbnail at arm’s length. The fovea is represented by a disproportionately large area – up over 50% – on the visual cortex in the brain.

color_vision

The rods and cones are found in the receptor layer of the retina. The receptors are connected to the bipolar cells, which are in turn connected to cells in the innermost layer, the ganglion cells. The axons of the ganglion cells are the fibers that eventually come together to form the optic nerve. The picture below shows the cellular organization of the foveal (right) and nonfoveal (left) retinas. Notice the higher density of cones, their one-to-one connection with bipolar cells, and the absence of ganglion and other cells in the foveal area. Rods, located only outside the fovea, converge in large numbers onto bipolar cells. Cones in the fovea are also smaller and more closely packed than in the nonfoveal retina.

receptor_organization1

This structure of the retina defines high visual acuity at the central retina and a low level of sharpness on the peripheral retina. The measurement of visual acuity is the minimum angle between two points, which are clearly seen as separate points. Humans with normal acuity 1,0 or 20/20 can distinguish two points separated by an angle of one minute of arc. This sharpest eyesight is observed in the foveola. In the inner annular zone of the parafovea, the visual acuity is 0,5 or 20/40 (an angle of two minutes of arc). Visual acuity of the peripheral retina is from 0,2 or 20/100 (an angle of five minutes of arc) within 13° of the foveola to 0.1 or 20/200 (an angle of ten minutes of arc) within 30° of the foveola, and to 0.025 or 20/800 for the edge of the peripheral retina.

vis_acuityThus, each eye has the sharpest vision in the foveolar area. Thanks to the effect of synergy, binocular vision creates better visual acuity than monocular vision.

ou-va

Each area of the retina is represented by an appropriate area in the primary visual cortex (V1), with its distinctive cell architecture, also corresponds to area 17 described by the anatomist Brodmann in the early 20th century. The primary visual cortex sends a large proportion of its connections to the secondary visual cortex (V2), which consists of Brodmann’s areas 18 and 19. Though most of the neurons in the secondary visual cortex have properties similar to those of the neurons in the primary visual cortex, many others have the distinctive trait of responding to far more complex shapes.

v1_v2

In a calm state, the visual cortex has minimal activity or passive vision. When gazing to examine an object carefully, a human generates an area of maximal activity in the visual cortex. I name the appropriate area of the visual field an area of active vision. Speaking metaphorically, eyes illuminate the object of examination. As we know, the sharpest vision is in the foveola. When a normal-sighted person is gazing at an object, the visual ray is narrow and the area of active vision is about 1-2°. But a lot of children use a wide-angle active vision anytime and anywhere. It’s similar to chewing with one’s mouth full, and the food is the visual information. Later the pernicious habit of permanent overloading the visual analyzer leads to nearsightedness.

The typical sign of wide viewing is the tendency to bring the object closer to the eyes, explaining the desire to see the object better. Imagine a dark room with a tennis ball you are looking for. Your eyes are a lantern whose beam is the width of a visual ray. While you are looking for the ball, the right action is to use a wide beam with ordinary light power to illuminate more area. As you see, in this case the visual ray looks like a cone with wide angle at the top and with a large area  in the base (Figure 1). When you find the ball using the wide ray, your next action is  to examine the ball and this action requires increased activity of the visual cortex. You can do it two ways:

1. You reduce the angle of the lantern beam, which increases light power to catch the object with the small area of active vision (Figure 2). This way, you will increase the light intensity and will be able to see it better at a far distance.

2. Saving the wide angle of the lantern beam, you come close and the ball fully occupies the area of active vision (Figure 3). In that case, you will also be able to see the ball better at a close distance.

less_area_means_better_vision

Thus, trying to see the object better, each child or adult makes a choice:

1. Decrease the wide-angle active vision, save the distance, and increase visual acuity, using the narrow-angle active vision (Figure 2). This action requires the proper visual skills and maintains better sight.

2. Save the wide-angle active vision, decrease the distance, and look at the object, using the large area of active vision (Figure 3). This action is comfortable and doesn’t require the proper visual skills, but leads to myopia.

This is my theory that answers the question, “Why do nearsighted people try to see things close to their eyes?”

The second question is, “Why do nearsighted people have mental strain when gazing at an object?” And my answer is, “Because they always use the wide-angle active vision”. As you see, at Figure 3 the person gazing at the tennis ball. The angle of the visual ray is wide and the area of the activity in the retina is large too. It means that a large area of activity exists in the visual cortex and the additional load on the brain creates mental strain.

One more difference between the narrow-angle active vision and the wide-angle active vision is saccadic eye movement. When normal-sighted children gaze at a big object using the small area of active vision, they make accurate and regular saccades to examine all the object, part by part. On the contrary, using the large area of active vision, children goggle at a big object with sporadic saccades. This is an authentic feature of a permanent wide-angle active vision. Usually this children have or will have a myopic refraction.

Improve your eyesight naturally.

Dr. Arkadiy Davydov

5 Responses

  1. mat:

    22.03.2010 at 21:34 #

    Tip of the top, crème de la crème Doctor!

    Having gone thru your latest theoretical material and looking back I can see that, with me, my visual trouble started out with resistance to what was there and unwillingness to see things as they were..

    The physiological “solution” I found back then on how to avoid life is in total agreement with your theory (or the other way around):

    Using wide range active vision made my distant vision worse and made me tired from overloading the visual analyzer, exactly what I needed: less analysis. But when I couldn’t see the tennisballs well enough anymore, a friendly eyedoctor came to my rescue with a nice pair of glasses, which I could even choose myself! Then I tried a little harder not to see differences, because these bloody lenses were in the way!. I succeeded again in seeing worse (and avoiding things in general), until another eyedocter came to my rescue and offered better “help”, if I could tolerate lenses. Happy with this new challenge (I wasn’t ugly anymore,) I got really bussy to build up a higher resistance to life (almost became a monk) and to make my wide angle vision more fixed. To help my poor sight I turned down on the sensitity of my tactile (by kickboxing and watching Van Damme movies). My sense of smell had given up all by itself over the years and my ears got obstructed with more and more and more wax.

    And as a crown on my labour I am now a nervous wreck.

    Incidentally, some weeks ago, one morning after doing my self-invented facial workout, I noticed something falling on the floor: it was a ballee of earwax. Another one was still laying in the other earshell. Hadn’t even noticed, cuase I am still far away from this awful thing called life, but I took a quick look…)

    So many respectful thankees Doc, for my increase in understanding of what the heck is going on here!

    PS: Until I read about the choices we can make to see something, I hadn’t realized that in my current efforts to reactivate natural eyefunction, I was forgetting to first do the wide angle part, lock on the object, and only then narrow down on it and start shifting.

    In the same reading I also came to think of the people I didn’t like for “searching” me all over in a conversation or so. I would surely never be so nervous and intrusive as they were!

    Mat

  2. Aglaya:

    14.09.2013 at 03:01 #

    Hello doc,
    found your website by accident, and so glad i did.
    Just to add to your theory. With my myopia of now (decreased) – 5,5 left and – 5 right eyes, and me normally not wearing glasses except for working on the computer and driving, (I had -8,5 and -6 respectively 5 years ago) – I ALWAYS find the smallest things I drop.
    I played golf for a few years refusing to wear glasses and was not bad at all! My close friends started to understand and all tried to better their vision as well. All of them gave up though. “too much work” I also play darts without glasses and score not bad either.
    To summarize and support your theory, given an interesting challenge – objective – we – myopes can re-find the way to the narrow angle active vision, to that narrow light beam (as it has to be for playing golf!). As it probably works in reading a super small print.
    Thank you very much for your encouragements and belief, as you can see, this is possible, and I will re-start my exercises again.

    Keep up the good work, hope you will come on the blog soon as i do have some questions as well.

    cheers

  3. Doc:

    24.09.2013 at 01:00 #

    Aglaya, good luck and let me know if you have any questions.

  4. Aglaya:

    24.09.2013 at 02:23 #

    Hello again, and thank you for your reply.

    My questions:
    a) my orthoptist never heard of Bates and will do the conversion exercises with me. She wears her near vision glasses at all times also. (No comments necessary) What do you think of this profession/occupation/any use? For me, you are doing this kind of training on your website and I will be recommending it to her, if you are ok with that.
    b) white glare after the exercises in my left eye, always comes after (wether i do one eye patching, sunning, or Gypsy Tables (have you heard of this – Medtafeln – meditation practice?, or conversion/diversion Gottlieb Presbyopia chart). It is my left eye that is lazying out, but i do manage to use both of them well.
    c) ears and eyes connection – too obvious, could it be sort of used, do you think?
    d) dyslexia – one of the reasons for myopia? I think I was one when I was very little BUT it was not an option to be a underachiever kid, so I was trained to use all I could to excel including glasses, right handed way of handling things (now I have some feelings I was very very left handed, but can’t remember), memorizing the lesson to know the right answer rather then think for myself, etc.
    and finally,
    last question:
    e) memory – loss, or blocks, so obvious, I do not remember so much, I hardly remember any of my childhood, and some blocks of my life as well. My city, where I lived for dozens of years, couldn’t remember the names of the streets of my neighborhood, when last visited. What is that about? And how it is connected to the eyes?

    I thank you in advance,
    cordially

    PS not need to say, when on my velo bike, without glasses of course, I see better, I actually see, because I am looking.

  5. Ionela:

    22.03.2014 at 15:10 #

    Aglaya, so happy to find somebody who can share same ideas with, yes it happens with me as well about remembering things from childhood also I was forced to memorize every single word from the lessons rather than using my own words (old european system) and right handed but even now I can fully write with my left.. thanks

Leave a Reply





Categories

Recent Posts

Subscribe

Enter your email:

Delivered by FeedBurner

Statistics