Eyeworm is one of the rarest types of worms in chickens. It is usually seen in troplical areas where the Surinam cockroach lives, since that is a host for the worms. There are some bogus videos online where people have claimed to have eyeworm, where it really may be pus in an eye from a respiratory or eye infection. Real eyeworms may be seen in the eye, and are about 1/8 inch long. Many people in Hawaii deal with eyeworms.
Valbazen given orally, and also diluted in the eye, as Coach 723 has said is the usual treatment. Repeat both treatments in 10-14 days. Some vets will also anesthetize a chicken and manually remove eye worms. 5% Cresol, a chemical once found in Lysol, used to be used to treat it.
If your chicken is having any symptoms, such as bubbly eyes, sneezing, crackly breathing or nasal drainage, it may be suffering from a respiratory disease.