Pfizer is in discussions with the US Food and Drug Administration (FDA) about altering its safety warnings on Viagra after reports linked the famous impotence treatment with partial blindness in some users.
So far the FDA has received 38 reports of sudden blindness among men who took Viagra, although the agency said it had not yet determined whether the pill was to blame.
The latest concern involves a type of blindness, referred to as non-arteric ischemic optic neuropathy (NAION), which usually affects men over the age of 50. It is caused by an interruption of blood flow to the nerve that links the eye to the brain.
In March, a report in the Journal of Neuro-Ophthalmology for eye specialists described seven cases of permanent blindness linked to Viagra.
Lead author of the report, ophthalmologist Dr Howard Pomeranz, said the drug may alter the circulation of blood to the optic nerve and that patients concerned about the risk could get an eye exam to determine if the optic nerve is already narrow.
