Why is Myopia on the Rise?

Babies are born with "short" eyeballs, so shortly after birth they are unable to focus on near objects. During early childhood the eyeball elongates until both near and far images are in proper focus. At that point, eyeball elongation generally stops. However, in some people the eyeball continues to elongate beyond its ideal length. The result is the common condition known as myopia, in which the person now sees distant objects as fuzzy and out of focus. Fortunately, the condition is easily corrected with corrective lenses or Lasix surgery.

The incidence of myopia has doubled among young U.S. adults in the past 50 years. No one knows for sure why, though there are some interesting theories. One is that we spend too much time on our computers, cell phones, video games, etc., looking at screens up-close. Another theory is that we don't spend enough time outside in the sunlight. The second theory is supported by research in animals showing that a neurotransmitter called dopamine controls elongation of the eye; too little dopamine throughout childhood and young adulthood allows elongation to continue, leading to myopia. And, as it turns out, dopamine production is stimulated by sunlight.

The theory that the rise in incidence of myopia might be due to too little time in the sun is interesting, but no one is suggesting just yet that spend more time outside. For starters, we don' have any idea just how much time in the sun might be needed to prevent myopia. And we wouldn't necessarily want to trade myopia for skin cancer when myopia is so easily corrected.