U.S. health officials are investigating rare reports of vision loss among men using the impotence drugs Viagra, Cialis and Levitra.
But, health experts caution, this type of vision loss also is linked to the same illnesses -- such as diabetes and heart disease -- that can lead to impotence.
The U.S. Food and Drug Administration said Friday that it had 43 reports of varying degrees of vision loss -- including blindness -- among 38 users of Viagra, four users of Cialis, and one user of Levitra, the Associated Press reported.
The vision problems seem to be linked to a condition called nonarteritic anterior ischemic optic neuropathy, or NAION, which causes sudden vision loss when blood flow to the optic nerve is blocked.
For that reason, it may be impossible for the FDA to determine whether the impotence drugs contribute to vision loss, the AP said.
Five patients had permanent vision loss in one eye and the other patient lost sight in both eyes.
All of these men had high blood pressure, diabetes, or high cholesterol -- again, risk factors for vision loss.
"It's potentially a serious issue," said Dr. Robert Cykiert, an ophthalmologist at New York University Medical Center and a clinical associate professor at New York University School of Medicine.
Viagra can cause blood pressure to drop, which may cause insufficient blood flow to the optic nerve, resulting in vision loss, he explained.
Bar Chama noted that the potential vision problems cited on the labels of these drugs refer to temporary blurred vision or a temporary blue haze, not the permanent effects the FDA is investigating.
He said that men who take Viagra often have high blood pressure and high cholesterol, which are also associated with the conditions that can cause blindness.