Larry Wan, DO, is an Optometrist in San Jose, California, specializing in computer vision syndrome. Here is an excerpt from his interview on the Sharon Kleyne Hour syndicated talk radio show on September 14, 2009 (www.modavox.worldtalkradio.com).
The primary effect of computers is to retard the normal reflexive blink rate. Most people blink around 30 times a minute, or 10,000 times a day. During intense computer use this can drop to as little as five times a minute. Each blink replenishes the moisture in the eye’s tear film and prolonged periods of insufficient blinking can cause the tear film to dehydrate.
Dry states (such as Arizona) are worse than humid states for dry eye caused by computers, and indoor conditions can be even worse on the eyes than outdoor dryness.
One problem with computers is that they are a different distance from the eyes than books, so glasses might need to be changed to accommodate this. Also, a computer image consists of thousands of dots (pixels), to which the eye must constantly adjust to keep the images in focus. In a book, the eyes mostly look at sharp, black and white lines. As a result, when working on a computer, the ciliary muscles in the eye that keeps things in focus are working constantly, which can be very tiring. While reading, they work far less.