Public Citizen petitioned the
Food and Drug Administration Thursday to add black-box warnings to the labels of Viagra, Cialis and Levitra, as well as the hypertension drug Revatio, which is similar to Viagra.

A small number of people taking the impotence drugs have developed NAION, or non-arteritic ischemic optic neuropathy, a loss of vision that is frequently irreversible.

So it's now clear, mastubation doesn't cause blindness but Viagra can.