I sympathize with you and getting thoughts like that out of your head is really hard. Maybe you can wear glasses or sunglasses whenever you are outside to reduce your fear and protect your eyes from any stray objects. Also, it is extremely unlikely that you would get anything in your eye while just walking around. Unless you are in a construction site which you can completely avoid. Whenever something you don't like pops in your head try and think of something positive or that makes you laugh.