The upper and lower eyelids have many functions. They protect the cornea [clear portion out front of the eye] and the eye itself from drying out, from insults and trauma from the outside environment. They spread the tears (tear film) across the cornea. The eyelids produce portions of the tear film from the meibomian glands along the eyelid margin and from cells in the folds of the eyelids. Finally, they assist in the draining of excess tears out through the tear ducts.
The eyelids of dogs and cats usually open between 10 and 14 days of age with no incidence. However, we can observe a congenital defect most frequent in the feline called eyelid agenesis. This defect presents at birth and demonstrates a lack of eyelid formation. The upper eyelid (lateral 1/3 to 2/3) fails to develop resulting in a full or partial malformation. Absence of eyelids can result in secondary trichiasis and exposure keratoconjunctivitis. Trichiasis is periocular hair that rubs on the cornea. In the case of eyelid agenesis, where a portion of the eyelid rim is absent, the cornea has no protection from the surrounding hair, therefore making contact directly to the cornea, which can result in corneal irritation, pigmentation, as well as corneal ulcers.
Exposure keratoconjunctivitis is the insult to the cornea and conjunctiva from constant exposure from the environment. If not treated, eyelid agenesis symptoms can be painful and uncomfortable. Most untreated patients develop scarring, pigmentation, ulcers, on the cornea. Surgery (blepharoplasty, cryotherapy) is necessary to correct this condition. Please contact your ophthalmologist if you notice this problem in your pet.