Maybe he has cataracts or photo-sensitivity.
The story ZD mentioned reminded me of the story of a rebbie who had invited a talmid for Friday night dinner. The talmid watched as the rebbie ate exactly seven spoonsful of soup. So the talmid did the same, even though much of his soup was left over in the bowl. After dinner he approached the rebbie and asked, “Rebbie, excuse me, but may I ask you the significance of your taking exactly seven sips of soup? You seemed to finish, but when I did the same thing, I still had much leftover soup.” The rebbie replied, “I used a bigger spoon.”