If there is any squinting and/or watering in that eye, you could have a corneal ulcer. If there's no discomfort associated with the spot, you can probably wait and watch it. Check with your vet when you can.
The 2 more common things are: corneal ulcer that is healing or corneal dystrophy also known as cholesterol deposits.
ulcers are painful and the dog would be blinking and in distress. Take him to the vet! Dystrophy is a breeders' choice and in Labs in link to diet on genetically predisposed dogs. Fish oil tends to contribute to the fat deposits.
