How long does it take for naphcon-a to work?

Another question?: Naphcon a shrinks blood vessels and makes the eye appear less red. However, the more important question is why your eye is red to begin with. Redness is a sign that something is not right with the eye. Masking it with naphcon a can sometimes lead to problems. There are some serious conditions, such as an infection, that need specific treatments. You should see an eye md for evaluation.

A few minutes: It should work pretty quickly.