Was he in direct sunlight? If so that could be why. If not watch him next time you take him out in daylight hours, if he keeps shutting eyes out in daylight hours it could be an internal medical issue or a vitamin A deficiency. Now I'm not saying anything is wrong with your cham just laying it out there. So just take him out for the next couple days in daylight hours. I'd do it around noon and just watch and see if he closes his eyes and leaves them closed for a long time. If so then it's time to see a vet