Light at Night Protects Diabetics' Eyes

Sleeping With the Lights On Could Prevent Retinopathy

From the WebMD Archives

June 27, 2002 -- An illuminating theory may lead to a simple way to prevent a common cause of blindness among diabetics. Researchers from the U.K. suggest that a condition known as diabetic retinopathy might be avoided by sleeping with the lights on. But they add that more studies are needed to prove that their bright idea can actually save sight.

Some 17 million Americans have diabetes, and roughly a quarter are believed to have some degree of diabetic retinopathy. The condition occurs when tiny blood vessels in the retina -- in the back of the eye -- rupture, but the exact cause of these ruptures is not clearly understood.

In a study published in the June 29 issue of The Lancet, Cardiff University professor Neville Drasdo and colleagues offer direct evidence that diabetic retinopathy is caused by a lack of oxygen, occurring within the inner layers of the retina during darkness. Previous research has shown that oxygen levels in the retina of diabetics fall as the eyes adapt to dark.

The researchers tested the effect of breathing in 100% oxygen -- normal air is 21% oxygen -- on the eyes of seven people with type 2 diabetes and eight people without diabetes. The diabetics had the disease for an average of about seven years. None of the patients had been diagnosed with retinopathy, but they all had evidence of too little oxygen within the retina during darkness.

With high oxygen treatment, the eyes of the diabetic patients returned to normal.

Drasdo tells WebMD that the findings expand on earlier research indicating a link between a lack of oxygen and diabetic retinopathy. He also suggests that it's likely that the lack of oxygen is what is causing the increase in blood vessels in the eye -- thus the retinopathy.

The researchers suggest that sleeping with the lights on could prevent retinopathy in diabetics because light through closed eyelids suppresses the eyes' ability to adapt to the dark. Drasdo says the nighttime light therapy would have to be permanent because it takes up to two decades for retinopathy to develop in diabetics. And he adds that the long-term consequences of this preventive treatment are not known.

"We believe that those consequences, if they exist, will be far outweighed by the benefits, but we don't know that for certain," he says. "So we can't actually recommend that people try this just yet."

While calling the new research "fascinating," retinopathy expert William F. Mieler, MD, of Houston's Baylor College of Medicine, agrees that it is too soon for diabetics to turn on their nightlights. Mieler is a spokesman for the American Academy of Ophthalmology.

"This is just one study with a very small number of patients," he says. "It is possible that (a lack of oxygen) is just one of many factors that trigger the development of retinopathy."