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To my dismay, viagra is regarded by most users as a "lifestyle" drug. It is often taken like candy without first taking medical advice. There may be some people taking it recreationally who are aware that mixing it with some heart drugs can be harmful, but that sort of awareness is uncommon.
More worryingly, I have been hearing warnings about blindness due to viagra use since 1998, when Dr Howard Pomeranz first alerted the eye community about it. Despite the serious nature of this side-effect, it has not yet (June 2005) been given a mention in the patient inserts for the drug, let alone spread into general awareness amongst physicians.
(Incidentally, this blindness is not to be confused with the "blueness of vision" effect on the retina, which is a reported side-effect in patient inserts. The side-effect we are now talking about is not a temporary blueness, but a blindness called non-arteritic anterior ischemic optic neuropathy (NAION)).
Only recently has this blindness hit the mainstream news, and the US Food and Drug Administration (FDA) is now investigating the issue.
The consensus at present (June 2005) by Pfizer and the FDA is that the number of reported NAION cases is very low considering the widespread use of the drug - 38 cases out of perhaps 23 million users, so that it is not a big issue.
NAION has been described as a sort of stroke of the eye. My worry is that taking a viagra pill may cause the eye-equivalent of mini-strokes, where each incident is not really noticed, but where the cumulative damage adds up over time. Perhaps NAION mini-strokes could be a called "silent killer of vision" in the same way that glaucoma is.
Another way of putting it: the vision damage done by viagra was noticed in the 38 users by the users themselves, and obviously linked with the use of the drug because they had just taken it within the last 36 hours. The noticed vision loss was sudden and dramatic, which was why they brought it to the attention of their doctors. But in a far greater number of people, vision damage may simply not be noticed or linked to viagra use. The vision loss may be "sputtering along" and only be caught at a late stage, just like is often the case with glaucoma.
While at this stage no one knows if NAION mini-strokes exist, my advice would be that anyone using viagra should at the very least have his eyes checked regularly by an ophthalmologist. In particular they should be made aware if their optic nerve cup/disc ratio is small. Pomeranz has identified a small cup/disc ratio as a major risk factor for NAION in his 2005 paper.
The bottom line is that further study is certainly needed, because it could be a very big issue.
