RoundwormRoundworm—Thelazia: Thelaziasis is caused from Thelazia species of roundworms. This one likes the eyes. Flies feed on lacrimal secretions and inadvertently act as vectors in transferring the larvae into the eye.
Thalazea worms in an eyelid
Symptoms include conjunctivitis (pinkeye) photophobia (sun sensitivity) and tearing. Corneal scarring can happen with chronic infection. You can actually see the worm move across the visual field.
Treatment is by removing the worm surgically and controlling flies.