January 03, 2006

Pirenzepine ophthalmic gel, a product of Valley Forge Pharmaceuticals, is currently being investigated as a potential pharmaceutical treatment to reduce the severity of developing myopia by slowing the growth of the axial length of the eye, with results thus far suggesting a 50% reduction in the progression of myopia in children. The product is likely to be available for market in two or three years, with the usual regional variations due to differences in regional regulation.

There is a market. Myopia among teenagers in western cultures has increased dramatically in the past few decades, frequently to as high as 80%. Eyeglasses are no longer the exception in a given population, but the norm.

Children are most likely to become myopic between the ages of eight and twelve. Researchers have noticed that the time period for the most drastic jumps in myopia during this age bracket -- and chronic glaucoma, loosely linked with myopia later in life -- have come simultaneously with the introduction of western-style education (the more study-focussed, the higher the incidence) and the sudden general pervasiveness of computers into all aspects of life (and especially personal entertainment); and have found a strong link between the incidence/degree of myopia during adolescence and extensive computer time. Links were also found between the incidence of myopia and amount of close reading/other near work, as well as an inverse corellation to time playing sports. (In animals, exposure to natural light seems to protect against myopia, but this link has not yet been verified in humans.) It is believed that to compensate for the intensity and duration of close focus needed, the eyeball actually changes shape to ease the effort on the eye. The result is an increasing loss of distance vision: myopia.

A bit of a positive feedback cycle here: if, as I suspect, those who wear glasses are additionally even less likely to participate in sports due to the sores and general unpleasantness that can result from sweat, concentrated at the point where the frames touch the skin.

If the science suggesting the root mechanism of altered eye shape holds true, the incidence of chronic glaucoma can be expected to increase, as the now permanently elongated eyeball blocks off the existing meshwork from siphoning off excess fluid, with a consequent increase in eye pressure. Currently only 2% of western populations over 40 develop chronic glaucoma ... but visual-screen computers have only been a prevalent part of our home, school, and office environment for two decades. If this theory is valid, over the next decade we can expect to see these numbers explode.

Another environmental effect which have been linked with myopia is diet: foods rich in sugar and refined starches have been linked both with increased myopia and with chronic glaucoma. The root mechanism may be heightened levels of insulin, which are matched by reduced levels of a chemical-binding protein believed linked to growth of eyeball and lens. Again we see the potential for another positive feedback cycle, where diet and genetics combine to evoke type II diabetes, which itself causes myopia and other eye complications due to insulin imbalance. Once damage has been caused, alterations in diet can only act to prevent further damage, not restore the eye to its previous condition.

There do also exist genetic components to myopia -- at least one gene has already been identified by Christopher Hammond (St. Thomas' Hospital, London UK) -- but for the most part genetics seems not be a causal so much as a protective factor against negative environmental influences.

To date the evidence, although fairly strong, remains almost entirely circumstantial; yet it would seem to be the path of wisdom to respect the potential indicated by such potentially potent links and take marginal precautions: limit time spent by children on a computer, encourage children to participate in outdoor sports, maintain a healthy diet.

Against such simple, basic lifestyle preventative measures, why wouldn't we seek a pharmaceutical solution first?

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