"Inhibition of the renin-angiotensin system reduced the advancement of retinal changes by 60 to 70 percent as compared with placebo, mostly likely independent of blood-pressure reduction," a group of doctors led by Dr. Bruce Perkins of the University of Toronto wrote in a commentary.

Mauer said more research is needed before the drugs could be routinely given to diabetics who show no signs of kidney or eye problems, especially since they may cause birth defects if given to pregnant women.

"But there are some people whose blood sugars are very difficult to control, who are developing early eye changes. It might be quite reasonable, given what we know, to institute this kind of treatment," he said.