There are a couple of things to address with this question. You can be light sensitive for a ton of different reasons. I can't tell what color your eyes are, but even people that have really light eyes, light hair, and just less pigment overall can be light sensitive. Yes, having corneal staining will make you more light sensitive, but you have to remember that your eye is not a flat surface. So you have your cornea on the front, but there is everything behind that that the light has to go through before it hits the back of your eye. If there is a cataract in there, or anything like that going on, that can also cause light sensitivity. There’s just so many things that can cause it. Corneal staining is one of them, but you did say that your tears evaporate in 4 to 12 seconds, which is pretty quick. 4 seconds definitely, 12 seconds is okay, but if your tears are evaporating at 4 seconds then your eyes are still super dry and the surface of the front of your eye is still not incredibly smooth.
Drs. Travis and Jenna Zigler