My dog has a clear subtance over his eye?

For quite a long time now, my dog has had a clear goopy circular lens type substance on his cornea. It tends to move around his eye from time to time and sometimes it's not even present. It's also slightly shriveled in the middle. My dog responds to it by blinking and his eye gets watery at times. I've read online that this issue could be due to poor malnutrition and my dog eats both human and dog food--could this be the problem? I'd like to get answers from either experienced dog owners or vets. Thank you.

what you read online, if written by vets or highly experienced dog owners, is most likely true. But it also depends on what human food you feed him. Dogs shouldn't eat the following: anything to do with peanuts, bread, citrus fruit (oranges, lemons, etc.), berries, chocolate, grapes/raisins, avocados, tomatoes, (they really shouldn't have any sugary treats), salty foods(don't give them too many chips/popcorn), or chicken bones.It could be mucus or from dust but that's least likely