I think we all know about the “risk” of nonarteritic ischemic optic neuropathy (NAION) and Viagra, but it hasn’t come up yet in my practice. I had one patient who became impotent from Timoptic!  Anyway, no one is really impressed with a cause-effect relationship- I think it’s pretty clear that the same risk factors that predipose to small vessel disease leading to ED are the same as in NAION, and that Viagra therefore doesn’t place the patient at risk. But for medicolegal reasons, I would probably tell the patient that it’s rare but possible, and make a note in the chart.