A Compendium on Myopia Rehabililation

[Tom]

Hypnoticity Revisited

The basic idea about hypnotic images is this:

Focusing on hypnotic blurs facilitates ciliary relaxation and retinal remodelling. This is especially true to an image composed of multiple, spatially-distributed hypnotic images (e.g., a bunch of white flowers in the grass, under moderately-bright sunlight).

OK. Time to invoke some guests again!

Tom> Here's Todd describing using sharp line to clear his vision

Todd> After days of working on pushing my range, I would look, for example, at electrical power lines and see a double sharp-blurry image. The sharpness and darkness of the power lines increased over several weeks. Now I see them sharply.

Tom> Todd then applies this to other objects.

Todd> It is especially useful to focus on sharp lines, such as overhead electrical transmission lines, and houses or trees with sharp edges.

Todd> I found it most helpful to choose objects with crisply defined dark lines or borders, such as telephone poles and power lines or edges of buildings. You’ll soon notice that blurry or “double” images will begin to resolve. I remember becoming excited when I started to see crisp power lines, and billboard signs, and could eventually start to read signs at a distance. 

Tom> Here Alex comes, talking about the benefit of printed letters, in today's blog.

Alex> Most of the eye charts you will see, share this trait.  It is usually letters, and if not letters, than shapes that mimic the concept of the written word.  Clear straight lines, predictable recurring angles, occasionally perhaps circles.  When you are actively working on recognizing an object at the edge of your focusing ability, having a known shape is of great help in achieving active focus.

Tom> Alex on the benefit of contrast.

Alex> It is rather more difficult to pull into focus leaves, blades of grass, or other patterns that may a) be in motion or b) not have a specific, singularly defining, predictable geometry.  Contrast further improves our ability to focus, so for many the black test on white background further increases the odds of pulling the writing out of the blur, into sharp relief.

Tom> Some thought on what to do outdoor

Alex> So when you are outdoors in particular, and the world just seems a bit blurry, find some writing.  License plates are my favorite, as they have very clear fonts, and occur at most any distance you might want to use.  Once you find a few of those, work on the focus there, you may find that the rest of your surroundings begins to resolve into greater clarity.

Tom> Instead of single letter, Alex recommends a letter string.

Alex> There are other factors contributing to this, which is why writing is also better than using simple geometric shapes.  You may notice that you can just read one or two letters – but once you do, the others begin to emerge.  The aspect of reading multiple strings of letters, resolving each, can help further focus your eye.  This is especially true once you are working more with double vision, rather than just blur

Tom> A bonus from Alex, referring to the so-called Placebo Effect

Alex> Your brain plays a sizable role in this.  We see this most clearly in children, that focusing just stops happening, when the child believes that the image is blurred.  The same is true for us adults.  Much as other aspects of our physiology cooperate when we believe that the feat is possible, providing a recognizable shape for the mind to process often jumps starts the process of the eyes focusing.

[Tom]

The short-term effect of overcorrection and undercorrection on axial length, while watching TV!

Studies on animals invading studies on human? Read on!

Gist of the study

Here's how this study goes: 14 emmetropes and 14 myopes undergo an experiment, in which every one of them has (only) their right eye's lenses undergo all 4 experimental conditions:

a) right eye with full prescription
b) right eye with 3 diopters of overprescription
c) right eye with 3 diopters of underprescription
d) right eye with a translucent diffuser, on the top of their full prescription

Immediately prior to the experiment, the subjects watches TV, located at 6m away from them (this is to relax their ciliary). They were then fitted with a lens on their right eye, and continue to watch TV for 60 minutes (so they are always focusing 6m away) For each subject, the experiment is conducted over 4 days, with one experimental condition (order randomized) each day, during a specific time frame (to avoid confounding other factors).

(by the way, reading through the paper, I can't help but think how well this experiment abides by the ethical guideline on human research )

Then what happened? Those with 3 diopters overcorrection had their axial length increased kind of (p=0.03). Those with 3 diopters undercorrection had their axial length decreased, for sure (p=0.0001). Those with diffuser also increases slightly (this is called form-deprivation myopia).

The reason behind the "kind of", and the "for sure," is that myopic defocus tends to be around many times stronger than hyperopic defocus. This means that the magnitude of axial length decrease, induced by underprescription, will be more than the magnitude of axial length increase, induced by overprescription of the same diopter.

My Conclusion

We all know what will happen if we are overprescribed. But now, the short-term effect of underprescription, an effect replicated in previous animal studies, is confirmed in human study too.

Notice that the change of axial length does not happen due to staying at the edge of blur. A 3D undercorrection puts one's far point at 33cm, so when a subject undercorrected this way is made to focus at 600 cm, he is exposed to accommodative stimuli of around - 1/6 - (-3) = + 2.833 D. Simply put, the myopic defocus in this case is just not minimal.

A plausible explanation of this experiment's result, is that looking far with more positive prescription substantially reduces ciliary tension. The change in axial length, which possibly affect the entire eyeball from cornea to sclera, could very well be accounted by the crystalline lens thinning triggered by ciliary relaxation.

You can read the study on your own here:

http://www.iovs.org/content/51/12/6262.full?sid=dbdaf664-6184-42eb-a8d7-e94008536dce

[Hillyman]

Hi Tom Lu,

You are a bright person - and can 'figure out' a lot of these issues.  But here a case where these people LOOK AT THE FACTS, and, "can't figure it out".  They are "searching for a *solution*....".

http://www.youtube.com/watch?v=xH_H4BRJMLk

I know how difficult it is to conduct, "just prevention" with a plus.  But these "research methods" do NOT include your use of your own "math skills" and scientific perception.

I gave up "asking" these people for any "solution" a long time ago.

Otis

Otis

I wouldn't be too harsh on the direction of this work. it looks like they are at least exploring the path of defocus as a factor in retarding the progression of myopia.  From the video, it seems the challenge is to provide this defocus effect while allowing the wearer of the DISC lens to have distance vision. It does seem that the idea of simply wearing a plus lens for near work and then just taking that off for distance work may be "too simple"!

I suspect also that including some level of technology--hey, it's a new type of lens--should also make the research more palatable to the optometry field as it validates the research being conducted, while introducing, if one were cynical, a new commercial product to sell to the public.

Nevertheless, I think we should be encouraged by this research, because it begins to introduce into the mainstream optometry thinking the defocus effect as a factor in myopia, instead of attributing the axial length growth in myopia as genetics. By and by, it may open the door for other approaches such as plus-lens and hormesis to be included in the picture.

[Tom]

Light and Myopia - An Incredible Connection

Intro

While walking outside, we sometimes get hit by a drastic increase of sunlight intensity, and then, whatever that was previously blurry, becomes crystal clear followed by a perceived increase in 3-dimensionality. What's going on?

Precursor: Outdoor Activities

One of the breakthroughs in eye research (most notably in the last decades) is the myopia-inhibiting effect of outdoor activities. It all started with epidemiological studies:

Study 1) Myopic children tends to engage in less outdoor activities. In fact, the amount outdoor activities seem to have more influence on myopia development than near work (there is no paradox here, we also know that near work can be done in ways that does not invite myopia development, this explains why in certain studies there are no significant association between near work and myopia)

Study 2) A longitudinal study also shows that children engaging in less sport and outdoor activities tend to become more myopic.

Study 3) Which one is it? Sport or outdoor activities? In 12-year-old children, the higher amount of outdoor activities is associated with less myopia, and not the sport being practiced --- It's the total amount of time outdoor that counts.

Study 4) Apparently, the environment plays the leading role in myopia development. When 6 and 7-year-old children of Chinese ethnicity of Sydney are compared with their Singapore counterpart, the Sydney group has substantially much less prevalence of myopia (3.3% vs. 29.1%). The total hours of outdoor activities per week (13.75h vs. 3.05h) was found to be the strongest factor associated with the difference in myopia prevalence (granted, the data are collected from the questionnaires, but the statistical and clinical significance is there).

These fairly-recent studies sparked a new momentum towards figuring out what makes outdoor activities so beneficial. One other study, showing that myopia progresses faster in winter than in summer, points to the possible link between light and myopia. Other researchers suspect Vitamin D, relaxed accommodation and sunlight-induced increase in retinal dopamine level.

Sequel: Lens-Induced / Form-deprived Myopia vs. Light intensity

The ensuing research split into different directions, occasionally leading to equivocal conclusions. But here are a few from the animal research:

Study 1) To test whether the intensity of lighting could have an effect on myopia. Rhesus monkeys are form-deprived under 2 conditions: normal lighting condition (up to 630 lux) and high ambient lighting condition (25000 lux). Both eyes of the ambient group become more hyperopic than those of the normal group.

Study 2) In chicks, exposure to either bright laboratory light or sunlight, even for just 15 minutes a day, substantially retards diffuser-induced form deprivation myopia. What’s more, the diffuser-wearing chicks who were exposed to only 15 minutes of sunlight a day are still more hyperopic than the non-form-deprived chicks under low laboratory light setting.

Study 3) This is a study with an unusual twist. Chicks under constant light, day and night, exhibit more hyperopia. However, if the chicks wear eye cover or have a hood above them to cover the light, for 12 hours a day, then it would protect them against hyperopia. For chicks, emmetropization is maintained by a regular diurnal light-dark rhythm.

Study 4) Young tree shrews who are form-deprived by living in darkness end up developing axial myopia. Refractive status is maintained partially through regular exposure to light.

Study 5 - Ashby and Schaeffel) This is the most interesting find so far. Chicks wearing -7D lenses were put into 2 conditions: low lighting (500 lux) and high lighting (15000 lux). The chicks under high lighting compensate fully for -7D at a much slower rate than their low lighting counterpart. What now? Other chicks wearing +7D lenses were also put into the same 2 categories, and the chicks from the high lighting group compensate fully for the +7D lenses at a much faster rate then their low lighting counterpart. Light inhibits lens-induced myopia and accelerates lens-induced hyperopia.

What's more, when chicks got injected with spiperone (a dopamine antagonist), exposing to high illumination no longer spare the chicks from form deprivation myopia. On the other hand, when the chicks got injected with a placebo solution, exposing to high illumination would show its form-deprivation-myopia-inhibiting effect again.

What to extrapolate from these?

In light of these studies, we speculate that:

In terms of image quality, the more intense the light, the smaller the pupil, which results in an increase of depth of focus. As the pupil constricts, the light rays that normally would scatter around the periphery (a.k.a., "optical noises") no longer make their way into your eyes. Consequently, aberration decreases and an increase in depth of focus and perceived clarity ensues (i.e., sharper image with increased contrast). Light provides clarity in a safe way, while reducing unnecessary staring tension at the same time - A brightly-lit image is clearer and more easily focusable.

Although the change in light intensity can be mistaken as clear flashes, distance gazing, under moderately bright sunlight, greatly promote double vision and clear flashes, possibly also in part through a significant reduction in accommodation and convergence.

There is a catch though. Sunlight alone is not the solution to myopia. The human folks in the studies only witness a slower myopia progression (i.e., not a improvement in dioptric terms), as they are still being overprescribed. Animal research suggests that light only reduces the speed of compensation to minus lens, and does not change the target refractive status the eye is compensating for.

Actually, we haven't even talk about the key finding. The Ashby and Schaeffel study did provide us with some clues as to how sunlight inhibits myopia. In that study, a dopamine antagonist essentially disabled the protective effect of sunlight - As the retinal dopamine (a neuromodulator) level decreases, elongation also fails to stop.

This strongly suggests that the process of elongation is in part modulated by....some chemicals in your retina! The biochemical component of axial length regulation could very well look like this:

Level of sunlight => Different levels of retinal dopamine/melatonin => Different rate of proteoglycan synthesis => Different choroidal thickness => Different level of resistance to axial stretching.

Oh. And here comes Dr. Alex:

Over the past 40 years between my father's practice and my own, regions with less sunlight, more rain, longer winters, etc, tend to bring us higher degree of myopia clients. Of course there are various other possible explanations we wouldn't discount ... however, the client with the desk job in the south of France almost always has a half diopter or even a full diopter less of a prescription than a very similar case in the north of the country.

[Note: On Dr. Alex's Oct. 29 blogpost, the relationship between ambient lighting and refractive status is explored.]

[Update: On March 18, 2015, Nature publlished an article titled "The Myopia Boom", essentially covering in less detail what you just read.]

[Tom]

Glycemic Index and its Potential Effect on Accommodation

It's good to know that several people brought up the issue of diet, and independently so.

Todd discovered that his vison is not so good with sugar intake. Dr. Alex also makes similar suggestions. Are they just instinctive hunches? For one, there isn’t lots of medical attention on diet, but then not every eye professional disregards it either. Here’s one that is in line with functional medicine, published in 2013.

Viewpoint: Sugar Stress: How Our Diet Impacts Vision and Development

Basic Ideas

Naturally-occurring food tends to have low Glycemic Index (GI). However, that changes when we start to manipulate food through industrialization and mass production. Food with high-glycemic-load are now everywhere.

When our body consumes such food, it leads to an abnormally high amount of sugar in our blood. In an attempt to maintain glucose level in our body, the hormone insulin is then secreted throughout the body. This dramatic increase in insulin, or hyperinsulinemia, activates our stress metabolism, which in turn change our normal behavior to a fight-or-flee response. In short, overabundance leads to hyperactivity - the regular consumption of high GI food, in high quantities, leads to the so-called adrenal burnout.

(the chronic excess in insulin also renders the body resistant to the effect of insulin (a.k.a, insulin resistance), which in turn destabilizes blood sugar regulation and facilitate the storage of body fat. For an introductory video, see Dr. Sarah Hallberg's Ted Talk on obesity and type II diabetes)

How does that affect vision? The stress response, induced by the high-glycemic-index food consumption, shifts our default focus to far, rendering some of us incapable of accommodating well, when engaged in reading task.This could, if not well managed, leads to extraocular strain, and then perhaps some vergence or suppression issues. The same stress can also exacerbate near stress and potentially increase the progression of myopia (in many cases, however, people simply develop a dislike towards reading, which could also spare them from becoming myopic).

Yet another slippery slope?

I would be reluctant to claim that in the absence of mechanical processes, high GI food would create a myopia epidemic as the one we are having today, but that is different from saying that high carb could interfere with the accommodation system, the same way that alcohol would do. Of course, We could have also argue certain individuals are simply less susceptible to "glucose overdose" and the ensuing hyperinsulinemia, but the fact remains that high GI food is extremely prevalent these days. They are the norm in Standard American Diet (SAD), and some other popular diets alike.

For the record, adrenal burnout is associated with a feeling of discomfort, dizziness, increased heartbeat, hyperactivity and mental fatigue! So this is definitely something one can test, should one decide to do it (for, say, 1 month).
Food and Eating Suggestions

If you are in the mood of reducing your blood sugar level (and the resulting insulin spike and adrenal burnout), you can use the following suggestions as your starting point:

• Maximize the intake of whole, minimally-processed food, which includes:
  
  
  • Real whole grain (e.g.,wild rice, non-contaminated brown rice,stone-ground bread made of sourdough, opt for non-conventional-wheat grains such as rye, spelt, buckwheat, Kamut and Khorasan).
    
    (Surprising, sourdough-made bread even goes well with people suffering Celiac's disease. How is that possible? It's because it turns out that integral breads are naturally low in gluten anyway! We'll continue in my blog, but here is a relevant paper)
    
    
  • Nuts - Although not for all people, nuts plays the crucial role of supplying proteins for people not on meats, eggs or milks.
    
    (if you have allergy to certain kind of nut, you should be thinking hard about why you get that in the first place. Is it because the nuts are contaminated? denatured? or is it because your immune system is compromised? More info here)
    
    
  • Real Dairy - Food derived from milk that is non/miniimally-pasteurized, non-homogenized, and does not contain harmful pathogen, antibiotics or growth hormone. When raw milk is inaccessible, opt for organic kefir or raw cheese. It turns out that real dairy products are naturally low in lactose!
    
    (Note: If food sanitation standard cannot be guaranteed, consuming the above food can lead to serious health hazard)
    
    
  • Vegetables and fruits - Avoid pesticide, herbicide, insecticide, which disrupts the endocrine system. upsets the sex hormones, causes infertility and sexual abnormality in animals, and kills the bees! (sometimes thought to be responsible for pollinating a third of our food) Avoid genetically modified food. Research extensively about the food manufacturing process before buying and wash the food throughly (especially the leafy vegetables) before eating.
  
  Whole-and-minimally-processed food does not include:
  
  
  • Most flour-based food (e.g., industrial bread, denatured-wheat, pasta, biscuit, pretzel)
    
    
  • Refined sugar and their derivatives (e.g., sorbitol, white sugar, ice cream, chocolate, snackers, cake)
    
    
  • Denatured food (e.g., white rice, white flour, white bread, enriched flour, food enriched with synthetic gluten, pearled barley, bread made with yeast). Learn more about denatured food by going to supermarkets
  
  
• Eat only when experiencing significant hunger responses, and only stop eating when experiencing significant satiety responses. The former trains the body to absorb nutrients more efficiently, while the latter provides the body with a reserve to efficiently handle metabolic stress.
  
  (calorie restriction was found to increase the lifespan for rats. Really, reducing food intake is a no-brainer, sustainable solution to health, as long as one doesn't starve oneself to death)
  
  
• Some eye-friendly food include carrot (beta-carotene) and unpolluted fish (high omega3-to-omega6 ratio) - Grandma was right all along

Here is Dr. Alex sharing a bit of clinical experience.

A good 30% of the success in vision rehabilitation comes from reducing the body's exposure to sugars / simple carbohydrates. The impact of eliminating sugar from the diet on vision is nothing short of astonishing, especially when paired with a good rehabilitative program.

The effects of diet would easily cover the span of a lengthy book. There are a number of vision related supplements, but I haven't been able to correlate actual improvements in vision from any of them. The largest immediately observable impact in diet is the relation of insulin spike to reduced response to refractive change in the eye. In the most basic terms, eating simple carbs triggers a reduced ability to focus clearly.

Individuals wearing glasses, functioning in familiar environments will not notice this change. But if you're actively working to maintain or improve your vision, those insulin spikes create a noticeable and frustrating setback during the "edge of focus" exercises.

Incidentally, Jake did some experimentation and found that intermittent fasting (which dramatically reduces one's insulin level), for as little as 16-24 hours once per week, is associated with increased visual acuity.

One the days after my intermittent fasts, I would get clear flashes to 20/40, where before I would only get double vision on that line.

I didn't put the fasting and the clear flashes together, for the better part of six months.  It wasn't till winter came, and I quit the fasting, that the progress stopped.

At first I blamed winter.  But then one day a blizzard snowed everything in, and I was forced to do a day of fasting, lest I wanted to brave deep snow and hope to find an errant open store.  The next day, I had the clear flashes again, which had been absent for several months.

That's when I started experimenting specifically with the fasting, and found that I could create clear flashes by doing the fast.

Additional Resources

Since we like to promote healthy diet regardless whether we are myopic or not. Here are some paper/presentation on how diet could possibly affect myopia (and trigger other health conditions):

• Garry Kappel's presentation on "Myopia and Nutrition" - Kappel takes a more integrated approach on diet and extends the topic beyond high GI food. To illustrate, he elaborates a bit on blood-sugar-controlling nutrients, some cornea/crystalline lens friendly nutrients, other nutrients for regulating intraocular pressure, and yet others for the connective tissues. These recommendations tend to be in line with Paleolithic diet and functional medicine, and more corroborating details can be found in the nutritional component of Myopia Manual. For the record, the Cordain studies refer to the readings below.
  
  
• Sorry. This should have been called the Cordain powerpoint instead. Loren Cordain is considered as one of the founding fathers of Paleolithic Diet, so don't be surprise if the contents appeal to many paleolithic concepts (e.g., hunter-gatherers, African tribes, Weston Price, unprocessed food). In this presentation, Cordain elaborates on the lack of myopia in rural environment, and hunter-gather societies. Instead of focusing on near work, Cordain chose to focus on high GI food and the impact hyperinsulinemia has on the body, and on the eyes. This will prepare us for the next readings.
  
  (Check out the chart on glycemic load (i.e., a metric that take into account both glycemic index and food portion). Technically, it's the glycemic load that we want to avoid, not high GI)
  
  
• Hyperinsulinemic diseases of civilization: more than just Syndrome X - High GI Food, plus susceptible genes, triggers a cascade of chemical processes that lead to unregulated growth of ocular tissues. This study attempts to claim that high level of carbohydrates could also trigger male vertex baldness, or certain skin diseases (e.g., acne, hyperpigmentation, skin lesion), or other more! (e.g., polycystic ovary syndrome, breast cancer, prostate cancer, colon cancer, increased stature).
  
  Most of us don't have a biochemical background, but the diagram on the top of page 102 worths checking out. As always, causal mechanism based on diet take tremendous amount of data to substantiate, so do at least appreciate their effort.
  
  
• Cordain et al. - An evolutionary analysis of the aetiology and pathogenesis of juvenile-onset myopia - Same old stuffs. I should mention that hyperglycemia was found here to increase hyperopia slightly, contrary to what Cordain and his colleagues claimed. There are many theories as to how this happened. Some speculated that an episode of glucose overdose triggers a slight change in the refractive index of crystalline lens, others think that it's due to the accumulation of polyol metabolites. In either case, they point to the possible link between high GI food, type II diabete and cataract.
  

[mailliam]

Hey TomLu, just had a read through some of your updated posts. They have been really useful.

Some questions:

You mentioned that myopic defocus tends to be around 5 times stronger than hyperopic defocus, can you explain why? (this is for my curiosity rather than for any practical use in vision improvement).

Regarding your conclusion in post #36, you said, "In a sense, this is problematic for IRDT, because underprescribing by 3 diopters put your far point at 33cm. Focusing at 600 cm, while your far point is at 33cm, can be hardly considered an incremental (myopic) defocus." I think because the defocus was applied to only one eye, the increment isn't as large as you describe here. I just tried holding up a +6 lens to my right eye only and I can still easily read.

Perhaps an alternative treatment for myopia could be glasses with a myopic defocus in one lens and a full prescription lens in the other. And two pairs of glasses prescribed to patients to wear on alternate days so that both eyes are given equal amounts of myopic defocus.

[Myoctim]

Hey TomLu, just had a read through some of your updated posts. They have been really useful.

Some questions:

You mentioned that myopic defocus tends to be around 5 times stronger than hyperopic defocus, can you explain why? (this is for my curiosity rather than for any practical use in vision improvement).

Updated the culinary rocking post. Enjoy,

Liam, the reason why researches conclude that myopic defocus is much stronger than hyperopic defocus, is because that's what they have determined experimentally. To figure out the causal mechanism would probably take decades or so. The effect of hyperopic and myopic defocus just doesn't add up linearly. You could overprescribe an animal by -5D all day all night and the animal's eye will compensate for that (i.e., end up getting -5D with a +- 1.5D offset), but if you let that same animal to look far without glasses, even for one hour every day, he'll probably only get -1D.

So 2 hours outdoor activity should compensate for 2*5h = 10 h nearwork?
But what if that ratio is decreased by genetic variation? Wouldn't such a person be predisposed for myopia?

Also it would be interesting at which pathway the cililary spasm triggers axial elongation. Does the cililary itself release myopic growth signaling molecules?

[Myoctim]

By the way, outdoor activities does not provide myopic defocus by itself. Actually, myopic defocus might not even be the main underlying cause of the myopia-inhibiting effect of outdoor activities.


As for the cause of axial myopia, it's not even clear if cililary tension is necessary to increase vitreous chamber volume.

But imagine going outdoors after an 8 h near working day and just having some ciliary spasm. There should be a high contrast myopic defocus counteracting axial elongation.

Concerning me I never understood why me getting myopic as a child of emmetropic parents and grandparents.
I guess my ancestors simply did spend much more time outdoors.

Looking at axial myopia, I did a lot of reading and AFAIK it is said myopes tend to underaccommodate e.g. reading with some hyperopic defocus. Is there any new research about that?

[Tom]

A Primer on Form Deprivation Myopia

At the time I posted the first form-deprivation-myopia draft, I struggled a bit with its relevance to myopia rehabilitation. As it turns out, form-deprivation myopia proved indeed to be, to some degree, relevant to myopia reversal, as the latter requires eliminating all major causes of myopia, which includes the regular exposure to an abnormal visual environment.

Form-Deprivation Myopia - Introduction

An old way to induce myopia in animals is through form-deprivation. Sometimes by suturing an animal's eyelid, and sometimes by forcing the animals to wear a diffuser, which would make images blurry.

The myopiagenic effect of form deprivation doesn't come instantly - it takes at least 72 hours of chronic deprivation for the effect to kick in. Form-deprivation myopia can be generated in human too, and this is apparent to patients suffering from ptosis (i.e., close eyelid) and cataract (i.e., intraocular lens clouded by protein deposits). Wearing a diffuser or living in darkness all day long is a good way to generate deprivation myopia.

In general, the longer the deprivation period, the higher the axial length. Somehow the lack of stimuli reduces the retinal dopamine level, without any ciliary involvement. The deprivation, or the lack of it, essentially controls the production rate of retinal neuromodulators, ultimately leading to choroidal thinning and vitreous chamber elongation.

However, if form-deprivation-myopic animals were exposed to light, then something miraculous happens - their myopia would be reversed, sometimes completely within days of exposure. Form deprivation myopia is modulated by light intensity and can be controlled fairly easily.

[In a very real sense, this shows that form-deprivation myopia is different from defocus-induced myopia, in that the latter has a more permanent effect. To be more specific, form-deprivation myopia differs from defocus-induced myopia in terms of time course and the effect of lighting (see http://www.iovs.org/content/42/3/575.full?sid=b0d00dcc-d543-4540-990a-cf58733fc201), so the use of form-deprivation myopia, as the main paradigm for the study of human myopia, risks of being way off the target.]

Form-Deprivation Myopia - More Details

We can still learn something from deprivation myopia though. For example:

a) Deprivation myopia is a type of axial myopia, albeit different from defocus-induced axial myopia. It raises the possibility that accommodation might not even be a causal component in the development of a typical human myopia (although that is not to say that accommodation can't be a symptom associated with myopia). In fact, we once thought that since atropine greatly reduces the progression of myopia and that it paralyzes the ciliary, so it must have been that accommodation plays a key role in myopia development. It turns out that atropine also greatly reduces form deprivation myopia (although defocus theory of myopia development might still work without accommodation).

b) There are some similarity between deprivation and defocus-induced myopia. Here are some key findings from deprivation studies:

Study 1: When monkeys wear a diffuser occluding their nasal field, they only become myopic in the nasal region. Deprivation myopia works in a regionally-selective manner.

http://www.iovs.org/content/50/11/5057.full?sid=8c773ab2-0e01-4e90-a1ca-66a22ac85846

Study 2: It's not a matter about just periphery or central field. When only the central field is occluded, chicks still get myopic, and the degree of myopia increases as we widen the occlusion range. We have to look at the eye as a whole.

http://abstracts.iovs.org//cgi/content/abstract/54/6/4040?sid=cd774c6a-12b8-4c67-9dfb-debb3cab5433

Study 3: Rhesus monkey can, in the not-so-severe cases, recovery from deprivation myopia too. Light plays a role in modulating ocular growth.

http://www.iovs.org/content/53/1/421.full?sid=39ce3f6b-3f4d-48a2-9815-df5935d710a2

Study 4: The eyes of rhesus monkeys become more prolate as they are deprived of visual stimulus. Visual stimulus modulates the shape of eyeball.

http://www.iovs.org/content/50/9/4033.full?sid=a19eebb8-6eda-42fb-b9bb-cf8d03b908f1

Incidentally, these four key points also summarize defocus-induced myopia pretty well.

[Myoctim]

(here is something I didn't want to talk about: it is possible that the reduction in axial length is not due to reduction in vitreous chamber volume, but only due to intraocular lens thinning, in which case the finding is not so useful, since we already know about how underprescription can relax the cililary)

Hi Tom Lu,
what's the problem with lens thinning?
AFAIK emmetropization is using lens thinning to compensate for axial elongation by stretching the lens in
emmetropic kids while in myopic kids it was found that process having ceased for some unknown reason.

BTW I always wondered about why frauenfeld success clients being less affected by presbyopia when getting older.
I think a shortened eye ball by retinal shaping won't be an explanation but a more flexible lens due to lens thinning
pretty much would.
But of course lens thinning wouldn't reduce the risk for retinal detachment

[Patrea]

I have been dipping into this and other myopia-related posts - for years, it seems! - could you post a summary of recommended actions .
I have made some progress, but it is keeping up the +lens exercises in a busy day that is tricky

[Hillyman]

As for your remark on presbyopia, I can say that this is not a resolved issue even among the eye professional community (almost nothing relevant to myopia rehabilitation is resolved, actually ).

The two dominant theories on presbyopia are that they are either due to age-related lens stiffing, or age-related loss in cililary flexibility. It could very well be a combination of both, or any other controversial theory, of course.

The Frauenfeld participants are almost uniformly myopes or former myopes, as a consequence most of them have been subjected to overaccommodation over a long period of time, so your sample is biased to start with, as myopes tend to develop more efficient accommodation system as a side benefit of "self-induced overcorrection." That's not to say that myopes will not suffer presbyopia - just that the presbyopic myopes are much better off than presbyopic hyperopes.

If I were to speculate, some presbyopia-related advice by Dr. Alex would be outdoor activities and focusing within far point for a brief period of time. Actually, I would be interested in digging up the incidence rates of presbyopia in hunter-gather societies, although this topic is about myopia only

Tom and Myoctim

Myopes have presbyopia at probably no different a rate than the non-myope population.  I've worn minus glasses all my adult life (-5.5), and starting at about my mid-40s needed a bifocals with a plus prescription in the lower part of the lens so that I could accommodate to the normal reading distance of 20 inches or so.  My plus add is 2.25. Most people who can afford them wear bifocal prescriptions as progressives, with each lens providing an incremental progression of plus-lens effect as one looks down; no bifocal line is visible in the lens.

I was also curious about Dr Frauenfeld's comment that the patients he has followed over time do not seem to encounter presbyopia as they get older.  And then I came across this:

http://www.i-see.org/gottlieb/presbyopia_chart.pdf

This is an exercise for reversing presbyopia. It was developed by an OD and involves overconverging the eyes so that one sees three dots from the two on the chart. He markets this separately on the Internet and he has some anecdotes of its efficacy.

What piqued my interest is that this is the same exercise in principle as the "three cups" exercise that was recommended by John Bershak, who was one of the earliest proponents of reshaping the eyeball for myopia reduction that I had come across. So the question is: is there some common ground in reversing presbyopia and reducing myopia--and thus the situation that we hear about regarding Dr. Frauenfeld's eye patients? It certainly would bring some interesting threads in vision rehabilitation together!

As a side note: I have tried the over convergence chart above. There seems to be some effect in that reading material seems clear at a reduced plus add.

[Hillyman]

Scharchar was thinking about reducing the distance between the lens and cililary (surgically?). It's the same story of mistaking symptoms as causes and treating the symptoms instead of the causes. We now know that presbyopia is just a normal part of aging (much as Alzheimer's), but we also know that some risk factors make people age faster, so why can't the eye professionals think along this line?

I remember reading Schachar on presbyopia. His theory was that the lens in the eye is one of the parts that keep growing through life, like the ear lobe, or the nose. So at some point (at 40+ years of age), the lens' diameter is big enough that the zonules become slack. The ciliary function still works, but part of its pull is used just to take up the slack in the zonules, so the lens has a reduced pull on it for it to "plump up" for near-focus accommodation. He had some experimental surgery to take up the slack by inserting very small inserts outside the eye around where the ciliary ring would be to stretch the ciliary ring itself. At least, this is what I remember about his approach--the idea borders on the scary, if you ask me. I can't seem to find any more reference to it in the internet, though.

There are older people who do not have presbyopia, and who continue to have full accommodation range into old age. That would be explained that the lens in their eyes grow much, much slower.  After all, there are old people with normal looking noses!

Schachar's theory that the ciliary pulls on the lens to make it plump up for near focus goes counter to the usual theory by Helmholtz that the ciliary relaxes for the same effect. I like his reasoning as to why this would make sense: biological systems do not function by relaxing in order to pay attention to something in the environment (such as near work).

[Tom]

Energy-Efficient Light Bulbs

Our increasingly-sedentary lifestyle leads to less exposure to sunlight, and more exposure to indoor lighting.

Not all light bulbs are created equal. Fluorescent light bulb, especially the poor-quality, yellow-colored ones, blurs your vision and might hurt your eyes. The blurring caused by these light bulbs is unlike the one caused by minus lenses, and induces a headache-like sensation that goes away hours after the exposure.

The best way to figure this out is to try it on your own. Light up your house with only incandescent / halogen light bulbs, and then change the bulbs to some cheap fluorescent ones. You should notice that with fluorescent lighting, everything appears blurrier. Not just that, even the fluorescent light bulbs themselves appear blurry when you look at them (as opposed to looking at other light bulbs).

Why is that so? Hard to say. Some speculate that the human eye has evolved to see under light generated by a incandescent source. The color spectrum generated by sunlight, or incandescent light bulbs, are very smooth across different wavelengths. The fluorescent lighting, on the other hand, has a distinctively spiky colour spectrum which unnaturally emphasizes some shades of green, for instance. In addition, it has also been said that fluorescent lighting produces ambiguous shadow, which is an important cue for human's perception of depth. This failure to produce shadow might be the precursor of eye strain and other ophthalmologic concerns.

Let's bring someone else into the conversation instead. Here is Adrienne Piggot talking about her experience with fluorescent light bulbs:

The fluorescent light bulb will often give me a headache, or in the worst case actually cause a migraine, in which case I’m in big trouble and I need all kinds of medication. [...]I have really debilitating migraines. The light from incandescents doesn’t affect my head.

[To be fair, she probably has some neurological issues. For most people, fluorescent light induces only a tingling sensation.]

Fluorescent light bulb does not exactly represent a sustainable source of light energy either. All fluorescent light bulbs contain a tiny trace of mercury. As such, they should not be disposed of carelessly, because mercury flows through the air if light bulbs break (which will most likely happen if it goes to the landfill). In addition, fluorescent light bulbs tend to emit an abnormal level of UVA and UVB, which can adversely affect the retina - the same way that overexposure to sunlight can affect our vision in the long run.

Is there any high-quality fluorescent bulb that doesn't blur vision? I personally haven't find one - not even those marketed as "full-spectrum". Plus, those with color temperature beyond 5000K tend to overstimulate our vision and possibly disrupt our circadian rhythm.

Before we jump into LED, there is actually one Madrid study subsequently picked up by media, showing the adverse effects of LED on the retina. Another subtle disaster in the making? 


Alternatives?

Dr. Alex prefers neodymium light bulbs. However, there is great diversity in terms of quality even among these! For example, the second-generation neodymium light bulb GE Reveal is meant for the mass consumption:

1) They are made of materials of rather poor quality.
2) The lighting tend to be less intense, requiring you to buy more.
3) They last, on average, 1000 hours.

[To be fair, it's not that they are terrible, but they are below the threshold of satisfaction  ]

Verilux, Chromalux, PureLite are some companies claiming to produce neodymiums of higher quality, although it's unclear whether their higher price is well justified. The one I have is Chromalux A21 Frosted 150W, but whichever one you like, the light bulb you choose should fit the regular E26 socket. This means that all you need is really a change of choice, which is not hard to do.

UPDATE: One of my Chromalux burnt out fairly quickly, due to its high wattage and constant, daily use. The others are still working fine. Apart from the wasted heat generated by the these light bulbs, they are really only inferior to sunlight.

No Easy Solution

The world has gone far to be able to un-modernize itself. Opt for sunlight when it's available. When background lighting is insufficiently low, turn down the screen brightness to minimize the staring-at-a-bright-light-source effect (avoid that awkward level of brightness). A brightly-lit room (with eye-friendly light bulbs) goes a long way to relieving eyestrain!

[OtisBrown]

When and how to move to a lower prescription:

http://frauenfeldclinic.com/prescription-reduction-timing/

Thanks!