http://www.stuff.co.nz/stuff/0,2106,3543394a11,00.html

`Impotency drugs Viagra and Cialis may increase the risk of sudden blindness in men with a history of heart attacks or high blood pressure, research suggests.

A new study published in the British Journal of Ophthalmology is the latest to suggest a link between impotency drugs and a condition which could cause sudden blindness in one eye; non-arteritic ischaemic optic neuropathy (Naion). The authors recommended doctors discuss the risk with their patients.'