It's never about the light, it's your eyes. Somehow, your eyes can be referred to as slow in dilating or contracting your pupils depending to your needs. this is why you get the tunneling effect whenever you close and open your eyes, your eyes can't bend the light properly enough before it gets to your optic nerves.

Or, the muscles there are not strong enough to maintain itself to be focused on the specific angle it's trying to view an image from.

If you're really uncomfortable with it, you should consult an opthalmologist. But you can go around it if you exercise it a bit from time to time.

It's your mind feeling the fear, not your eyes.