NEW YORK (Reuters Health) - New research supports the theory that hours of complete darkness increases retinal damage from diabetes--and that sleeping with some lights on could help counter the effect.

However, it's too soon to recommend diabetics keep the bedroom lights on every night to cut their risk of the eye damage--known as diabetic retinopathy. For one, chronic exposure to light during sleep could have "some unforeseen effects," the new study's lead author, Dr. Neville Drasdo, told Reuters Health.

Diabetic retinopathy is a common complication of diabetes that can lead to blindness. It is caused by changes in retinal blood vessels.

Drasdo, of Cardiff University in Wales, explained that some researchers believe that oxygen deprivation in the retina during dark hours promotes diabetic retinopathy.

In their study, Drasdo and his colleagues looked at seven adults with type 2 diabetes but no apparent retinopathy, and compared them with eight non-diabetics. They found that activity in tissue near the surface of the retina was reduced after being in the dark, but was bumped up with exposure to oxygen. Healthy individuals showed no such changes.

The findings are published in the June 29th issue of The Lancet.

According to Drasdo's team, all of this suggests that "night-time illumination" during sleep could benefit diabetics. Drasdo said he thinks that keeping some lights on at night is "absolutely" a feasible way to ward off diabetic retinopathy.

However, he added, more research is needed before diabetics start taking on a permanent, "full night-time illumination" regimen.

It is unclear, according to the researcher, whether sleeping with the light on regularly might have negative effects such as sleep pattern disruptions.

Drasdo also noted that sticking with a diabetes management plan aimed at controlling blood sugar levels can help ward off diabetic retinopathy.

SOURCE: The Lancet 2002;359:2251-2253.

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