Guinea pigs have a paurangiotic retina: blood vessels in the retina are visible only near the optic disk, which makes the retina appear avascular on examination.2,3 Their eyelids are open from birth, and they have small third eyelids.2,3 Compared with other mammals, guinea pigs produce very small amounts of tears, which can predispose them to conditions that can affect corneal health (eg, ulcerative keratoconjunctivitis).2-4
Corneal ulceration can be attributed to trauma associated with bedding, hay, caging, a companion, hair impingement on the cornea (trichiasis), decreased tear production, or infection.1,4,5 Because of their naturally low tear production, some breeds may be predisposed to ulcerative keratoconjunctivitis (ulceration and corresponding inflammation of the cornea or conjunctiva).1,2 Another potential cause of corneal lesions in guinea pigs is neoplasia, specifically lymphosarcoma,2,6,7 which reportedly can infiltrate the cornea.1,2,6,7