Claustrophobia is a problem, but I don't think it would be the biggest problem. The biggest problem would be someone messing with my eyeball.
But do you know it's coming? They'd have to strap my head down to keep me from flinching. I go see my eye Dr. I let him do his job, but I don't like the idea of being present when someone is shaving off parts of my eyeball (or however they do it - they're still messing where I don't want them to).You don't exactly see the needle, and you don't feel a thing. It's totally numb.