Does a lot of exposure to sunlight lighten or darken your eyes?!

No, all that happens to your eye color with time is that they may lighten and start to look "blurry" in old age as cholesterol is laid down in front of the iris.

The only exception is for some drugs. In the case of the new eyelash-lengthening drug Latisse, the iris can be permanently darkened with a brown tinting.

nope..age will lighten your eyes...and sometimes drugs will change their color..( my mother-in-law had cancer and her cancer meds changed her eye color from brown to blue, but they went back to brown when the drugs were stopped.)