Apparently there is an issue with Viagra causing blindness in some users.
The FDA is investigating a number of these cases. If you go to
https://www.lawyersandsettlements.com/case/viagra_blindness_class_action
there is more information on this problem, some interesting articles, as
well as what you can do about it. There is also a free case evaluation
provided for those who might have been affected by this. I hope this may be
of some help.

kr0