I take sildenafil (Viagra), which temporarily gives a blue tint to my vision. Recently I was also diagnosed with macular degeneration. Will taking sildenafil worsen that? —Name and address withheld

Probably not, but few studies have looked into it. Sildenafil affects vision by blocking an enzyme that helps the eyes process color. But the limited studies available, mostly funded by drug manufacturers, show that effect is transient and appears to have no long-term effect on eye function. A few small studies of patients with macular degeneration or glaucoma taking sildenafil have shown the drug doesn’t worsen either condition within up to five hours of taking it. 

The only eye condition that’s been associated with sildenafil use is a rare blockage of blood flow to the optic nerve that causes a sudden, permanent decrease in vision in one eye—though it’s not clear what role the drug plays, if any, in the condition. If you experience such an impairment, contact your eye doctor right away.