Author Topic: A Compendium on Myopia Rehabililation  (Read 66254 times)

Offline CK333

  • Newbie
  • *
  • Posts: 11
Re: A generalized system for myopia reversal
« Reply #15 on: July 19, 2013, 10:58:27 AM »
Thank you Tom, I see your point.  I do admit that I need more distance viewing time/exercise, as I can see just how important it is.   :)

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #16 on: July 20, 2013, 03:41:45 AM »
If you intend to go on not wearing glasses, then since your far point is around 20cm, you shouldn't try to look too too far away. You can't just take off your glasses and expect it to improve (that might work for pseudomyopia, but not axial). You got to work on some active focus-promoting thing like focus pushing or dipping.


Thanks for your reply. I understand focus pushing to be "working at the edge of the blur" to encourage the eyes to focus a little farther out (for myopes). What is dipping?

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #17 on: July 20, 2013, 09:48:50 AM »

Thanks for the lead to your July 14 post. I had not seen it before, and by coincidence this morning I posted something on my thoughts about the Feldenkrais method for working the blur! It's essentially the same thing taking advantage of the same principle that you described in dipping but more at near point.

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #18 on: July 23, 2013, 12:08:08 PM »

Thanks for your continued postings. I want to understand your latest entry and I am tracking through the past postings to find your definition of "far point" and "maximum starting point." Can you point me to the postings? I got the "equilibrium point" definition.

Also, you mention "zonular spasms" and in other postings the zonules being tense. This strikes me as odd, as I have always understood the zonules to be nothing more than suspensory fibers from the ciliary body holding the lens in place. The zonules and the ciliary body are not antagonist pairs, but please correct me if I am wrong.

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #19 on: July 23, 2013, 04:18:49 PM »
I am not sure where this idea comes from that the zonules can become relaxed or tense. They are suspensory fibers whose only function is to hold the lens in place, and also transmit any contraction or release of the ciliary muscles to the lens.

I agree in principle with the theory of accommodation as you describe (I quotebelow), and the relationship between what happens in the ciliary muscles and the lens: when the former contracts, the latter thickens. But the zonules do nothing; they do not relax or thicken, and certainly do not exhibit a counter response to what the ciliary muscle is doing. If you find it counterintuitive that the action-reaction is such (one might think that only when the ciliary muscle relaxes does the lens become thicker), Schachar has a great theory.  I have seen it described elsewhere in this forum, using the Mylar birthday balloon as an analogy.

As with the zonular fibers, no, I think you are exactly right. Regardless which theory of accommodation you are subscribed to, standard textbooks suggest that zonules can not control itself, so cililary and zonules can't be antagonist pair. But what is still true is that when the cililary contracts, zonules relaxes, allowing the lens to thicken. And when cililary relaxes, the inner radius (of the cililary ring) increases, and the zonules (suspensory fibers) are now tense, allowing the lens to get thinner.

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #20 on: July 24, 2013, 12:25:27 AM »

But even Schachar's theory is still crucially similar to Helmholtz's, in the following sense: when cililary contracts, the anterior and posterior zonules become less tense, and when the cililary relaxes, the anterior and posterior zonules become more tense. That's why I said they work in "opposite direction."

In this context, the distinction between equatorial/anterior/posterior zonules becomes crucial, because the equatorial zonule does the exact opposite of what anterior/posterior zonules do. Of course, they are tense all the time, but that doesn't convey this subtlety.

I think the word you want to use to describe the state of the zonules is "taut," rather than "tense." This is because "tense" suggests an active change of state initiated within the zonules, whereas they are merely acted upon by the ciliary muscles. As an analogy in general musculature, a muscle gets "tense" resulting in the tendon connecting it to the bone becoming "taut" (and not "tense").

As to the roles of the equatorial/anterior/posterior zonules, it appears that in fact the anterior and posterior may have different roles and do not work in concert against the equatorial zonule as you suggest. See

"Since the anterior and posterior zonules do not attach to the
lens in exactly the same manner, the respective effect of each
might also be different. The asymmetry in the anchorage points
and orientation of the anterior and posterior zonular fibers
suggest a different mode of action of each."

I think, though, we can probably leave the subtleties of the Zonules of Zinn (my favorite body part name) and continue to focus on the more interesting quest for improving vision. My latest fascination, based on my two weeks in this forum, is the realization that there could be some feedback loop between the tension in the ciliary body and the sclera and choroid layes in the eyeball, that the tension in the former promotes a thinning of the latter two, hence the elongation of the eyeball--in effect, they "speak" to each other into myopia. Talk about subtlety! Of course, through the defocus approach, we are trying for the reverse the signals!

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #21 on: July 28, 2013, 03:13:47 PM »

I like very much your highlighting the increase in the blur that is the effective mechanism to get the eye to improve. This is something worth practicing.

Offline Todd Becker

  • Administrator
  • Sr. Member
  • *****
  • Posts: 442
Re: A generalized system for myopia reversal
« Reply #22 on: July 28, 2013, 03:26:47 PM »
Staying at a slightly blur object is not the thing that helps. It's the incremental increase in blur over time, instead of the incremental blur....The object doesn't need to be close or far - it depends heavily on the ability of the eye to detect the increase in blur, rather than its ability to detect blur.

Tom, I think this is a very interesting idea.  It's a dynamic version of generalized blur-point defocus therapy.  It could be applied to print pushing, with or without plus lenses; or merely focusing around the blur point at various distances.  You may indeed be right that focal-feedback neurology of the eye detects changes in focus/defocus near the blur point better than it detects the absolute degree of defocus. 

Your self experimentation seems to lend to support to this idea.  It would be good to devise some controlled experiments comparing the dynamic defocus method vs. the static defocus method.  Or let's see if others try your method and report their results here.

Good thinking!


Offline Tom

  • Newbie
  • *
  • Posts: 36
    • The Sustainabilitist
A Compendium on Myopia Rehabililation
« Reply #23 on: August 09, 2013, 10:34:06 AM »
Close Work - Making it Beneficial


One of the factors affecting your recovery speed is the way you engage in close work. Regardless of which prescription you are using, you should take close strain seriously.

Lighting for close work

Close work is best done under moderately bright sunlight. If not possible, try to recreate the same environment indoor, with overhead fixture or standalone lamp.

Avoid using poor-quality fluorescent light bulbs. I'm not the only one who suffered from fluorescent light use. See Dr. Alex's post on this here. For more? See Energy-Efficient Light Bulbs.

When reading on a screen (e.g., computer, smartphone), adjust the screen's brightness so that it's on par with the level of background lighting (which should be very bright). Reading under an overly bright foreground, along with a dark background, invites pupil dilation and with light burn.  8)

When done with the adjustment, try to read at the farthest distance possible, while making a conscious effort to relax. The light intensity increases "exponentially" as one moves towards the screen, so it's always a good idea to keep that in mind.

Prescription for close work

The single most myopiagenic activity is to read with a strong minus lens, which has the potential of inducing hyperopic defocus (either due to accommodation lag, or inherently prolate eye shape), or overconvergence (and its associated side effects). One should read either with the weakest minus lenses, or without glasses.

[Edit: The issue of eyeglasses frame got picked up. On the March 11 (2014) blog entry, Dr. Alex recommends frames with minimal border. This is yet another way to free up the peripheral vision. In general, we only want to correct the central vision when using minus lens, so a smaller frame without border is desirable. For those using plus lens, a bigger frame would tend to positivitize peripheral defocus, and hence is preferred for myopia rehabilitators. Personally, I prefer aviator-style frame with peripheral add, because they are stylish and sufficiently large, to the extent that one can't detect the frame border within one's visual field.]

A traditional minus spectacle has an uniform power across all meridians. Consequently, reading at one's far point with these minus lenses might still induce hyperopic defocus in the periphery. One way to minimize that defocus, is by adding positive cylinder value to your prescription (e.g., -3D with cylinder +1D at 0° axis, as a reading prescription of a -5D non-astigmatic myope). The 0° axis is preferable, since reading is usually done from left to right, in the horizontal meridian. Positivizing cylinder value is applicable regardless of the strength of reading prescription (e.g, be it -4D or +1D).

(Until lenses with peripheral design are widely available, it's pretty tough to eliminate peripheral hyperopic defocus at all meridians, while maintaining zero central defocus. However, if you use contact lenses and are resourceful enough, you should be able to obtain concentric-design bifocal contact with peripheral add online)

Several Tricks

To read as far as possible, one needs to find ways to increase the reading distance. This can be done by:
  • Projecting the screen onto a TV
  • Increase the size of the text
  • For higher myopes, read with a pair of pinhole glasses with holes <=1mm
  • For lower myopes, read with no glasses (or a weak plus lens, if possible)
Here is Donald Rehm's recommendations on focusing distance:

The book or other material should be held as far from the eyes as possible. The distance from the elbow to the knuckles of the hand has been suggested as the minimum working distance. If the book can he propped up beyond arm's reach and read in this manner, this is even better. If you own or can afford to buy a projector that can project the pages of a book onto a screen across the room, this is better yet. In fact, this type of projector should be in every schoolroom and used by the teacher as much as possible in preference to asking the students to read from their books. If you ever watch a group of schoolchildren studying or writing, and pay particular attention to the distance between their eyes and their desks, you will note that many of them literally have their noses in their work.

When reading, the child should look up and into the distance momentarily at the end of each paragraph, or at least at the end of each page, to relax the eyes. Ideally, the chair should be placed to enable looking out a window or across the room when looking up.

[For similar ideas, see Dr. Alex's distance-vision tricks]

Ultimate Trick - The Magnifier Hack

My experience with close work is that reading at 1m (or beyond) with naked-eyes, in an open visual surrounding, essentially eliminates all near stress, thus allowing one to read hours upon hours without noticeable side effects.

For myopes of -1D or less, reading at this distance is easily achievable. For higher myopes, this is still doable to a certain extent, with the help of full-screen maginification programs, and fairly mobile keyboard and mouse (e.g., wireless keyboard):

  • For Mac users, there is a built-in magnifier application allowing you to zoom in with COMMAND + OPTION + "+" (or zoom out with COMMAND + OPTION + "-")

  • For Windows users, DesktopZoom is one such program. No installation needed, just unzip and run DesktopZoom and press the START button. You can zoom in with CTRL + Mouse Wheel Up (and zoom out with Mouse Wheel Down)

Computer Work - Font and Color Scheme

The choice of background and foreground color can drastically affect our ability to perceive contrast. Black text under white background provides optimal contrast, without significantly reducing light intensity.

Similarly, An eye-friendly font should have consistent stroke thickness and minimal ornamental features. This would minimize the need to stare at them.

Instead of reading close with a default-size font, one should increase the font size so that reading can be done beyond one's arm length (or preferably, twice the arm length), but perhaps not so big so as to make navigation inconvenient.

A good color-and-font scheme goes a long way in terms of maximizing contrast and minimizing staring tension, convergence. Here is an illustration of a black-under-white, Century Gothic Regular scheme (16pt to 36pt are fine).

How to Engage in Close Work

The first issue of close work is the intensity of near stress. The closer the distance, the more the close strain. To minimize near stress, we need to look rather far away:

Read at a distance beyond 50cm. And think about ways to increase that distance.

On his August 11, 2013 blogpost, Dr. Alex puts: 
Simple fix, is to create a work environment where the most comfortable position is at the very edge of your focusing ability.

A much subtler way to reduce close strain, is to "free up" the periphery:

If you place the screen/book against the wall, consider displacing them in the middle of the room instead - We only want to obstruct the center of our visual field while reading. Engaging close work in a distant peripheral environment substantially reduces unnecessary near stress. Even chicks agree:

Quote from: "Physical Factors in Myopia and Potential Therapies" by Foulds and Luu
It has been shown in chicks with lens induced myopia the viewing of a near target confocal with the retina but on a transparent background so allowing more distant visual information to contribute to the retinal image, that the myopia was reduced or eliminated, but only if accommodation were intact.34 In this situation, with the eye accommodated to the distance of the near target, additional distance visual information would add a proportion of myopic blur to the retinal image. As myopic blur is known to be protective against myopia, the presence of a proportion of myopic blur in the image appears to have been sufficient to overcome the degree of myopia that had previously been induced in these chicks by negative lens wear.

Here's a rule of thumb:

If you are not experiencing a bit of far tension, or you start to feel close strain after a while, your working distance is probably too short.

Reversing close strain

In the worst scenario, you can undo near-stress symptoms via near-stress relaxation, which just means doing the following 3 things all at once:

  • Temporarily wearing a plus lens
  • Gazing into the distance (e.g., 2 m or beyond)
  • Relax convergence by adopting peripheral vision

The duration of near-stress relaxation period should reflect the duration of close work. Personally, if I do x minutes of close work at arm length, I would also need x minutes to completely reverse the near-stress symptoms (for the record, I don't work at arm length unless I have no choice).

In light of the previous remarks, the following suggestions are in order:

Eliminate any close strain before any near work. Eliminate any close strain after any near work. In particular, eliminate any close strain before going to sleeping, as tonic accommodation can prevent near stress from dissipating.
« Last Edit: May 25, 2015, 05:19:34 AM by Tom »
The Sustainabilitist
Stretching Further the Concepts of Sustainability and Resilience
Facebook   Twitter   Google+

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #24 on: August 10, 2013, 02:47:12 PM »
The underlying difficulty perhaps is to show that the myopic person's starting and final prescription is correct - I can easily conceive a scenario where a myope claims to have recover from -3D, while the truth is that he was overcorrected by 1.5 diopters and that all his myopia was cililary.

Ciliary or axial, I would take any reduction I can get!

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #25 on: August 25, 2013, 07:59:19 AM »

As a reply to your post #49, this "blur gazing" you speak of, is this just reading something at the edge of the blur and trying to clear it? I just want to be clear of the terms you are using, as your explorations always seem to produce interesting tangents of new thinking.

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #26 on: September 03, 2013, 06:52:08 PM »
4) Focus at the letter E, 5 minutes with your left eye (both eyes open), 5 minutes right eye, and 5 minutes with binocular vision.

The maximized letter E provides a great quality of contrast, because it's a black letter on a white background with well-defined contour. This creates a great environment that we usually can't take for granted, if the blur-gazing were done in other environment (which I prefer).

When you consciously focus peripherally on the letter E, you might feel that something around your retina, as if something is in your eyes. It's a tingling sensation making your eyes watery and numb.


OK, help me out here: What do you mean by "5 minutes with your left eye (both eyes open)"? Is it with both eyes open or just the left and the the right, and then both?

Are we looking at the E directly, which is what your instructions would suggest, or "peripherally," which is what your ending paragraph is saying? Which is it?

What exactly is it that we are doing when we are "blur gazing"?

Offline Hillyman

  • Jr. Member
  • **
  • Posts: 59
Re: A generalized system for myopia reversal
« Reply #27 on: September 04, 2013, 08:04:47 PM »
Who is the author behind the myopiacure blog? I cannot see a name anywhere.

Offline chris1213

  • Jr. Member
  • **
  • Posts: 76
Re: A generalized system for myopia reversal
« Reply #28 on: September 04, 2013, 10:57:21 PM »
I know that website author's name is Corinne.

Offline Tom

  • Newbie
  • *
  • Posts: 36
    • The Sustainabilitist
A Compendium on Myopia Rehabilitation
« Reply #29 on: September 07, 2013, 09:00:48 AM »
Glossary and Q&A - Part I

If you have any suggestion or question that you think deserve to be here, I'm all ears. I myself have tons of questions to figure out, so I cannot be relied on in terms of addressing specific individual concerns.





        Near Stress

Distance Ranges

An object is said to be:
  • in the near distance range if it's within 0 to 2 meters (equiv., 0 to 6.5 feet) from the observer
  • in the middle distance range if it's within 2 to 4 meters (equiv., 6.5 to 13 feet)
  • in the far distance range if it's beyond 4m (equiv., beyond 13 feet)
Having these terms at hand will help simplify several higher concepts in Far-Stress Method.

Far Point

If you're myopic, objects from far will appear blurry to you (with naked eyes), but if you move closer, and closer, the objects will become clearer, and then clearer. The far point is the farthest distance, such that you can still see objects in perfect focus. However, far point can be altered by wearing a prescription:

1) Wearing plus lenses decreases your far point.
2) Wearing minus lenses increases your far point.

Reading within your far point can increase your myopia, by inducing the so-called hyperopic defocus. The first step towards myopia reduction is to read beyond your far point, and undercorrected lenses can be very useful for that purpose.


Ever notice some images appear clearer than others, despite both being located at the same distance from you? An image is called hypnotic if it's perceived to have:

a) Well-defined contour
b) High contrast (i.e., dbrk under a light background; light under a dark background)
c) preferably, large and has only one color inside the contour

These properties make hypnotic image less effortful to focus on. Consequently, hypnotic images are perceived to be more "pleasant."

Different images vary in terms of hypnoticity. An example of a highly hypnotic image would be a big black circle under a white background.

It's possible to increase hypnoticity of an image, by getting closer to the object, or by increasing the intensity of light.

Who are you?

A fellow human being researching myopia on his own, through:
  • Self Experimentation
  • Cramming on Research Studies/Theses/Books/Other Publications
  • Brainstorming about Theories

What are your intentions behind your myopia advocacy?

I have been diagnosed with myopia and given a prescription probably since I was around 8. I have been becoming more and more myopic since then. By the time I realized the harm full-time wearing of minus prescription has done to me, I was already around -8D.

I have then been trying to find solutions to stop/reverse myopia for almost a decade, and I only got some substantial breakthroughs fairly recently when I realized that myopia is primarily perpetuated by short focusing distance, and compounded by the wearing of minus lens.

Armed with these information, I know that I now have a duty to speak out - as there is the possibility that if I don't, the public might only be informed of our progress on myopia decades later. Since the Web is full of not-so-correct information, I knew that people suffering myopia deserve better - The Compendium on Myopia Rehabilitation is my way of providing accurate and up-to-date information that adheres to my own standard.

Being a person with high myopia, I have seen the profound effects of myopia on my own well-being. I certainly don't want history to repeat itself for millions of other people, and the Compendium represents my contribution in eradicating the myopia epidemic.

Where can I find practical and accessible information about astigmatism (and cylinder lens)?     

What are the pros and cons of pinhole glasses?

A minus reading prescription provides clarity by re-projecting light onto (and around) the retina. The downside of this approach is some bundles of light could be projected behind peripheral retina, thereby inducing peripheral hyperopic defocus.

An alternative way to obtain clear vision, during close work, is through the use of pinhole glasses. Contrary to the mode of action of a minus lens, pinhole glasses ensure that light land on the retina, by filtering out the peripheral beams of light. This peripheral filtering reduces unwanted spherical aberration and retinal defocus, leading to an increase in depth of field (i.e., wider range of clear vision).

Many people notice that holding one's arm immediately above eye level would increase visual acuity. Pinhole glasses essentially operate on the same principle - only in a more sophisticated manner.

For people with -2D of myopia or less, reading can be done at a reasonably far distance. Consequently, using pinhole glasses for close work is not necessary. However, for people with higher myopia, reading distance would be too short without minus lens. In such cases, pinhole glasses can be used instead to read at farther distances. Doing so would eliminate minus-lens-induced-near-stress that would otherwise occur.

Although pinhole glasses provide clarity in a relatively safer way, it is still not without its drawbacks. One of its side effects is that it over-restricts peripheral vision, making it unsuitable for activities requiring attention to the entire visual field.  Another side effect is the dramatic reduction of incoming light, which then needs to be compensated by increasing background light level.

Since peripheral vision and ambient light are both necessary for normal emmetropization, the continued use of pinhole glasses (e.g., more than 2 hours at a time) is not recommended, as it could trigger form deprivation myopia.

(No sweat though. The time course of form deprivation myopia differs from that of lens-induced myopia, in that the former would recover as one reverts back to normal visual environment. Form deprivation myopia is only a concern with substantially longer deprivation period  (e.g., >24h), in which case the eyes might recover only to a limited extent.)

How do I know if I'm feeling near stress?

Here is Kathi talking about her experience:

I do notice when my eyes get tired form reading and feel pressure behind them when my glasses are on that goes away when I take off my glasses.

Kathi noticed that near stress can be triggered either by close work, or by minus lens. Notice that she talked about pressure behind her eyes, This symptom is called posterior ocular pressure. In clinical jargon, this corresponds to an increase in vitreous chamber depth.

Here is Alex_Myopic's experience of near stress:

Something that I forgot to mention is that when I was fully prescribed -2,25D and wore them for hours I had a strong feeling at the end of the day to wear them off because of eye strain. I thought it was due to the heavy metal of the frame but even now I wear the same frame and I don't have this feeling, so maybe it was due to the inner eye strain full correction minus provoked.

Here is Asli Han experiencing near stress, as the result of focusing close for a sustained period of time:

When I use computer without glasses and read-from 25-32cm, usually in half an hour I feel my eyes getting tired

For myopia rehabilitation, should one use bifocal rather than two separate pairs of glasses?

Personally, I can't recommend doing that. While using bifocals (with appropriate prescriptions for both near and far) for far activities is not really harmful for low myopes, using such bifocals for near activities amounts to overprescribing oneself. This is because while engaging in near work, the top portion would then induce hyperopic defocus on one's upper retina.

In other words, just because one have learnt which portion of bifocal to use for which activity, doesn't mean that bifocal won't affect them. In fact, countless peripheral-hyperopic-defocus studies, both on human and other animals, invariably suggest otherwise.

Can higher myopes use prescription that only corrects one eye?

The approach of correcting only one eye is called monovision. Why on earth would someone do that you ask? This is because even though the oculars receive images of different levels of clarity, after the transmission of electric signals to the primary visual cortex, the brain integrates the two images into one. As a result, the subject actually gets clear binocular vision.

Monovision is not a bad idea, as it enables clear vision without compounding near stress in the uncorrected/undercorrected eye (as a sidenote, you may have to deal with the resulting double vision on your own, if the disparity between two eyes becomes large). There are studies on monovision that alternates the corrected eye. In fact, monovision studies provide the definitive evidence of the harmful effect of negativizing prescription. Monovision is also a solution for presbyopes, which allows one eye for far vision, and the other for close vision.

What are the pros and cons of using traditional minus spectacle to do work at the far point?

Using an undercorrected traditional minus spectacle at one's far point is certainly less harmful than using a full correction, in the sense that the former eliminates central hyperopic defocus which would otherwise occur with the latter. It makes no sense to use a stronger minus prescription, when a weaker prescription can achieve the same task, while creating less near stress.

However, since the posterior retina is not a flat plane, using a traditional minus spectacle, even when reading at the far point, will still overcorrect your eyes in the periphery. This phenomenon of light projecting behind the retina in the periphery, also called peripheral hyperopic defocus, has been extensively shown to worsen myopia.

In fact, more is true. It turns out that any overcorrection/undercorrection, in any meridian, can have an effect on the eyeball, and that effect tends to manifest only in the region affected. In other words, defocus is regionally selective.

Therefore, traditional minus spectacle, which is designed simplistically (i.e., imposes defocus uniformly across all meridians), needs to be used with extra caution. One way of mitigating this issue, is by choosing a minus spectacle with extremely small frame, while taking great care to focus beyond one's far point. Smaller frames for minus prescription prevent the periphery from being overcorrected, and so does reading beyond the far point.

Would it be a good idea for higher myopes (e.g., -3D or more) to rehabilitate with plus lens instead and read at a closer distance?

While reading slightly beyond one's far point, either with naked eyes or with plus lens, seemingly induces the same amount of defocus. In reality, there is something more at play.

In December 2013, we toyed precisely with the idea of reading at the edge of blur with plus lens at close (i.e., 10cm). While we acknowledged the resulting increase in blur definition and text magnification (as induced by the plus lens), and the resulting clear flashes after each session, it also wasn't long before we observe a worsening of myopia over time. After some more observation and experimentation, we also realized that the worsening was primarily caused by the substantial increase of near stress. A bit more research then revealed proximal accommodation as the main driver of such near stress.

To be a bit more pedantic, proximal accommodation was originally discovered by measuring refraction of subjects who were asked to read through a tiny pinhole - a practice which would eliminate primary optical defocus. Earlier research found that proximal accommodation increases along with the decrease of reading distance, at a rate of approximately -0.2D per diopter of accommodation load - A finding consistent with our daily experience with near stress, which is hardly relieved by the effects of even stronger plus lens.

To further complicate the matter, the effect of proximal accommodation operates in a regionally-selective manner. This means that reading in a narrow corridor can still induce proximal accommodation in the ocular periphery, and this is even if the corridor measures 6 meters or longer. Without devices to trick us into believing that the objects are coming from far, the only way to relieve proximal accommodation is to read in an environment with a radius of 1 meter or more.

In practice, this means that while a -3D myope might get away reading at 33cm with naked eyes, higher myopes should, in general, consider using the tools at their disposal (e.g., increased text size, magnifier, pinhole glasses) to read at farther distances (e.g.,1m), while taking active steps to reduce the duration of each near work session.

What are the risks of using thick optical lenses?

While optical lenses are designed to be transparent, as the lens thicken, an unintended effect invariably occurs. Namely, the light rays would become significantly diffused by the lens, and non-stop exposure to diffused blur has been shown, both in animals and by us, to induce form deprivation myopia.

In fact, we were able to replicate form deprivation effects on our own, through the prolonged use of strong minus lenses, strong plus lenses and sunglasses. However, we were also able to recover from form deprivation myopia, provided that these lenses are not used for too long.  This is consistent with the findings on the time course of form-deprivation myopia, and the time course of its associated recovery.

In practice, this means that if thick optical lenses are to be used, they should be removed every hour or so to allow the eyes to recover the resulting optical distortions. However, a far more sustainable solution would be to obtain high-index lenses of the same diopter, as the stronger bending power of high-index lenses allows for thinner lenses to be crafted.

For some technical details on form deprivation myopia, see here.
« Last Edit: May 25, 2015, 05:25:04 PM by Tom »
The Sustainabilitist
Stretching Further the Concepts of Sustainability and Resilience
Facebook   Twitter   Google+