Is there any medical reason why a person would lose their eyesight after taking and ed drug and how common is that?

See answer below: While vision loss is listed among the most serious adevrse events of therapies used for erectile dysfunction such as Cialis for example, it is not a common side effect.

Remote possibilty: There is a condition called anterior ischemic optic neuropathy (aion). It is generally seen in older patients with pre-existing vascular disease secondary to hypertension, diabetes, and/or hypercholesterolemia. Pde5 inhibitors used to treat ed have been associated with aion. So any symptoms of visual darkening or loss should prompt discontinuation and seeing dr.