I'm no doctor, but there are two points that even I can make:
1) 38 reports out of 24,000,000 users is less than 0.0002 percent. Very small number. But who's to say that number won't grow after several years? Which brings me to my next point...
2) Apparently there were many reports of distorted vision when users first began taking v****. The reports included colors changing, not just blurriness. This implies an association between the drug's effects and vision. Since there are no reports of such vision distortion with propecia, I don't think propecia will ever affect our sight.
Man, do I feel bad about those guys who really rely on v**** to get it up, though. Even though the percentage is incredibly small, v**** hasn't been out THAT long, so I'm guessing there will be more reports of blindness. Also, small chances or not, risking eye sight is a huge deal.