Of the untreated eyes with progressive disease, 43 percent got worse, usually to legal blindness, researchers said.
Without treatment, 50 percent of retinopathy cases improve to better than legal blindness, or 20-200 vision.
If untreated, vision can become severely impaired to the point of legal blindness.
The treatment also reduced the risk of progression to legal blindness.
New York State defines legal blindness as having corrected vision of 20/200 or worse.
It afflicts one person in four older than 75 and is the leading cause of legal blindness in Americans over 55.
With virtually no help from elected officials and most national veterans groups, it took me until 1998 to receive benefits for Vietnam war-related legal blindness.
Kuwait is one of many nations that share the 6/60 criteria for legal blindness.
In 1994-1995, 1.3 million Americans reported legal blindness.
It affects 15 million Americans and is the biggest single cause of legal blindness among the elderly.