Sunday, December 06, 2009

Myopia .

Myopia .

Andre Willers

4 Dec 2009

Synopsis :

Progressive myopia is driven by the peripheral focus being slightly longer than fovea focus . The eyeball elongates to compensate , making the fovea focus myopic .


See important article in NewScientist of 7 Nov 2009 p49 "Generation Specs"

Progressive myopia .

Peripheral vision is the evolutionary driver . It is more important for the organism to have good peripheral focus than good central (fovea) focus . Sheer geometry dictates this . The peripheral vision covers a much larger area than the fovea . It is critical for the organism to notice any small change in this peripheral space . (ie predators) . Fine focus is thus more important in evolutionary terms for the peripheral vision .

While we normally think of the eyeball as static , it actually adapts in length to keep the peripheral vision in focus . This makes the central fovea part blurry . Myopia results . To make matters worse , corrective lenses tend to shift the peripheral focus back . The system then tries to compensate by lengthening the eyeball more . We get progressive myopia . You need stronger and stronger glasses .

Myopia and open-air .

A strong correlation was found between time spent outdoors and myopia .

The study was done on about 1200 Chinese children in Singapore and Australia .


Sydney children : 14 hr/week outdoors led to 3% myopia.

Singapore children : 3 hr/week outdoors led to 30% myopia

The critical factor seems to be time spent outdoors . It is theorized that light intensity (influencing dopamine production , which reduces eyeball–growth) and distance focusing and peripheral vision have the major effects . Excercise seemed to have very little effect .

Optimization :

From the above rather sparse data , a first approximation is

MyopiaRate = k / OutdoorRatePerWeekSunlight

Where k = 0.007857 +- 36%

Rather iffy data , but at least the error rate is below 38% (a critical Reserve Rate See "New Tools" )

This gives an optimal OutdoorRatePerWeek of about 19.88% .

About 17 hours of sunlight per week .

Optimal :

About 2.5 hours of visual exposure per day to sunlight will give you the best return on minimizing myopia . (for children , at least)

If dark glasses are used , they should ideally be darker towards the center and lighter to the periphery . The higher intensity light should be on the peripheral vision receptors .

Cheap and Nasty :

Dip your finger in a clear fat (preferably chickenfat) , but ghee or olive-oil will do . Trace three concentric circles around the center of the glass-lens .

The oily circle-lenses will sharpen focus on the peripheries .

A primitive Fresnel lens .

You can smudge the center of the lens slightly to reduce light intensity .

Note that long-term wearers of glasses always have oily finger-smudges around the rims . I used to think that this was laziness to clean , but now it seems it is an adaptive response to give better vision .Note that the whorls of fingerprints give micro-lens effects .In effect , miniature fresnel-lenses . Personalized , nogal .

An interesting effect:

If the lenses are clear , the person perceives a dizziness as the head is moved side-to-side . If the edges are smudged , this effect disappears . (I have just tried it , and it works)

The Rim-effect .

This brings us to the boundary effect of the edges of glasses . This is a discontinuity . Neural-networks are not good at discontinuities , especially varying ones like moving your head rapidly while wearing small glasses .The peripheral vision and the central vision does not match up , and the sensorium battles to keep up .

Hence the effects of smudged glasses .

A delicious example of stochastic resonance . Increasing randomness increases the quality of information .

We artificially smooth the quality of information around the rim and then rely on hardwired stochastic resonance effects to build a fairly reliable picture in the sensorium .

An obvious application would be in bi- or tri-focal lenses . Smudge the interfaces . Not a phasing of lightspeed , but a randomization (ie smudging) of information around the interface of the lenses . If it is built in , the eye will soon not display the smudge in the sensorium . But the effect will last .

Reversing myopia .

The elongation of the eyeball is a response to an environmental stimulus and should be reversible . Special glasses refocusing the peripheral vision should do the trick .

Glaucoma .

This should be monitored , especially if a quick and dirty method like smudging is used . The glasses should stay smudged . Cleaning them occasionally will lead to glaucoma as the system gets confused as to whether the eyeball should contract or not.

Tubular lenses .

It has long bothered me that the top predator on the planet has such a seemingly inefficient optical system as blood veins in front of the of the optical receptors , like in the human retina .

But it is more efficient in the peripheral view areas . The slightly out-of–focus image is focused by the tubular fluid blood vessel , which is transparent . The resultant data is assembled and stripped of extraneous data (like red-blood corpuscles) , then the resulting composite is more accurate . Note that this relies heavily on off-site computation in the visual brain . Why humans can use it .

Click .

The percussion compression effect of a Click from the mouth travels through the upper-palate to the eyeballs . The pulse is from underneath , and slightly lengthens the eyeball . Myopic individuals can perceive a slight increase in clarity (I have done it) . I would estimate it at about 5% . Not much , but noticeable . The neural networks do notice . The trick is to enhance it into a training regimen . More anon .

Itarin .

I will have to strip it down and rewrite it . It worked fairly well to postpone myopia by about 10 years . But it was built on the supposition that the fovea was the driver . Since the peripheral vision systems seems to be the driver , a rethink is in order .

Here's looking at you .


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