Problems affecting the eyelids may be congenital (present at birth) or may occur as a result of injury, infection, or exposure to various types of irritants.
Entropion is the turning in of the edges of the eyelid so that the eyelashes rub against the eye surface. It occurs in foals as a congenital defect. It may also be acquired in older horses as a result of chronic eye irritation or eyelid scarring or spasms. The turning in of eyelashes or facial hairs causes discomfort and irritation of the conjunctiva and cornea. If untreated, the condition can cause scarring, abnormal coloring, and possibly the formation of slow-healing sores or ulcers on the cornea.
Early spasms of entropion may be reversed if the cause is removed or if pain is lessened. Turning the lid hairs back away from the eye with stitches in the lid, injections of medication into the lid close to the area where the lid is turning in, or using anesthetics to block the nerves in the eyelids are some of the methods that have been used to lessen the pain. Established entropion may require surgery to correct the defect.
Eyelid lacerations (rips or tears in the eyelid) are common in horses. They must be repaired quickly to avoid infection, reduce swelling, and prevent further damage to the eye. In many cases, your veterinarian will clean the wound and use stitches to repair it so that minimal scarring occurs. A hard eye cup may also be necessary to protect the wound so the horse does not injure it further. In some cases, the eyelids are temporarily sewn together to protect the cornea. Your veterinarian may also recommend topical and oral medications to treat infections and reduce pain and inflammation.
Inflammation of the eyelids can result from the spreading of a generalized inflammation of the skin (dermatitis), conjunctivitis (inflammation of the conjunctiva), local glandular infections, or irritants such as plant oils or sunlight. Infection with certain fungi or bacteria can also lead to inflammation of the eyelids; however, this is uncommon in horses. To treat blepharitis, your veterinarian may recommend both oral and eye medications. Frequently cleansing the eyes with a warm washcloth may also be necessary. Closely follow your veterinarian's recommendations. For example, some topical medications that are applied to the eyelid may not be safe for use in the eye.
Parasites, such as eyeworms and the larvae of stomach worms (Habronema species), are a common cause of blepharitis in horses, particularly during warm-weather months. Treatment is targeted toward removing the parasites by the use of appropriate antiparasitic drugs, although eyeworms can sometimes be removed directly from the surface of the conjunctiva using forceps. If needed, topical ointments to reduce swelling may be prescribed.
Also see professional content regarding disorders of the eyelids in animals.