I am afraid to take Viagra because I may go blind.!!!?

I have some ed problems I am 27 and this has been going on for many years i attribute it to smoking lack of ual development cause of marijuana and smoke mild nerve damage. I get like 75% s it sucks really messes my life up cause of it i have never had or had a girlfriend. I have total testosterone of 700 ng/dl but i know more test are available because sometimes i do nor desire . I got viagra from doctor and am to afraid to try it i have read that it blocks something called pd5 to your eyes this can cause color changes and weird vision but... I have also read if you have a common eye condition where the nerves behind the eyes are tightly clustered puts you at risk for permanent blindness. This is often seen in normal people with great vision like me I see really good. because the nerves are so tightly clustered complete blood loss and blindness will occur. I don't wanna take that risk you see any advice..