Danny McDougall got a brand new computer last year when he turned 13. After getting
caught visiting some 'adult' websites, he's been banned from all computer use
after 11pm when he should be in bed. Danny isn't taking this lying down: "I need
my computer — I'm on there 24/7," he argues. "Besides, it wasn't anything
hard core," he adds sheepishly. "Mom told me it makes you go blind — but
everyone knows that isn't true. Is it?" While there's pretty much no truth to
this, heavy computer use, on the other hand, may be linked to the development
of glaucoma, according to a large Japanese study in the December Journal of
Epidemiology and Community Health. "Every second patient is bringing this
study into my office this week," laments Dr Yvonne Buys, a Toronto glaucoma specialist.
COMPUTER
SCREEN-ING
The study involved 10,202 workers with an average age of
43, randomly selected during routine staff medical exams at four large Japanese
companies. The employees completed questionnaires about their computer use, both
at home and at work, and any history of eye disease. Computer use was assessed
according to how long the desk jockeys had worked with computers, measured in
five-year blocks, as well as the average amount of time spent staring at the screen
per session. Risk factors generally associated with glaucoma like high blood pressure,
age, smoking, refractive errors and family history of the disease were also recorded.
Finally, the researchers screened patients for visual field abnormalities.
The test revealed that 522 employees had visual field abnormalities. An in-depth
eye test revealed that about a third of these workers had suspected glaucoma.
There was a highly significant link between these visual field abnormalities and
heavy computer use among workers who were short-sighted, and a less significant
link among those who were far-sighted. In fact, all
of the apparent risk of glaucoma associated with computer use was concentrated
in the subjects who needed corrective lenses of one sort or another — heavy
computer users without refractive errors were actually slightly less likely to
show evidence of glaucoma. They also had a low incidence of other ocular diseases
such as cataract and diabetic retinopathy. The researchers attributed this, not
to a protective effect of computers, but to a "healthy worker effect," since these
subjects happened to be affluent and highly educated. COMING
UP SHORT
The authors speculate that the optic nerve in short-sighted
eyes might be more vulnerable to computer stress. But they acknowledge weaknesses
in their study, particularly the fact that it was cross-sectional in design. Additionally,
subjects in this study had generally used computers for many years, but the screens
of 15 years ago are beasts compared to the ones available today. It may be that
this study is picking up a harmful effect that's no longer there. Dr
Buys is also skeptical of the study methods. "There are many problems: it was
a cross-sectional study, there was no control arm, and their diagnosis of glaucoma,
based on one visual field error, is not what we would use here," she argues.
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