The risk of blindness in your glaucoma patients may be higher than you think, even though you’re treating the disease.

Researchers at the Mayo Clinic reviewed the medical histories of nearly 300 open-angle glaucoma patients from 1965 to 1980. They found that 20 years after diagnosis and initiation of treatment, the probability for glaucoma-related blindness in at least one eye was about 27% — 9% for both eyes. Risk was especially high among patients whose glaucoma went undetected until nerve head damage had already occurred. The "classic glaucoma" patient had a 54% probability of blindness in at least one eye and a 22% probability in both eyes.

These findings contradict the results of other studies saying glaucoma rarely leads to blindness. The Mayo Clinic authors point out, however, that some of the most effective treatments only entered practice in the 1980s, so future risk estimates of blindness may be lower than these findings.