General: Entropion is the inward rolling of all or part of the eyelid and can affect anywhere from one to all four of the eyelids. The result of this eyelid inversion is that the hair from the eyelid skin rubs on the corneal and conjunctival surfaces. With mild entropion, in which there is little inversion and contact with the ocular surfaces, there may only be low-grade discomfort and excessive tearing. When the irritation is severe, however, the patient will have chronic pain and serious injury can develop. Self-trauma, due to the irritation, can contribute to the overall damage as well. Entropion is a significant problem because if it remains uncorrected, it will persist as a chronic source of discomfort. Ultimately, sight can be affected because of corneal inflammation, scarring, pigmentation, and/or ulceration.
Most developmental (primary) entropion demonstrates a clear breed predisposition. Although the genetic basis has not yet been clearly defined, the problem is likely the results of genes responsible for overall head and facial conformation. The problem is common in Shar Peis, Chow Chows, Bulldogs, Pugs, Retrievers, and Rottweilers. It is occasionally seen in cats as well, where it is typically a secondary type of entropion.
Most cases of primary entropion will deveop by 6 months of age. Occasionally, spontaneous (primary/developmental) entropion will not appear until after 12 months of age, especially in large breeds of dogs. Entropion is usually a surgical disease. However, entropion in an immature animal may improve spontaneously with growth. Mild cases in young dogs may be managed medically or with temporary eyelid "tacking" sutures until maturity. Surgery might be delayed until the age of 4-6 months, except in severe and complicated cases.
Trauma, chronic inflammation, and painful eye diseases can lead to acquired or secondary entropion. "Spastic entropion", which results from eyelid spasms due to ocular pain, might resolve with placement of temporary tacking sutures and control of the underlying painful eye disease(s). It is more likely to resolve if addressed early and aggressively. Surgical correction might be necessary, but the entropion will recur if the underlying cause goes uncorrected or uncontrolled. The cause, location, and extent of entropion and presence of concurrent problems determine the corrective technique recommended.
Success Rates: The success rates with surgery vary somewhat based on the breed, age, and specifics of the case. In general, surgery is successful about 90-95% of the time. In up to 10% of patients, there are extenuating circumstances (e.g., young animal, recurrence or persistence of underlying causes if secondary entropion, other) that necessitate a second procedure.
Cats: Entropion in cats most commonly results from a severe or chronic herpetic infection of the eye. Unfortunately, by the time it develops it is typically permanent damage and does not resolve with successful treatment of the underlying infection. Surgery is usually required to resolve this type of secondary entropion. This is one case where control of the underlying cause is critical since herpes in cats is commonly a chronic or recurrent problem.
Pugs: It is common for Pugs to have entropion of the inner aspect of the lower eyelid. The result is that the eyelid hairs rub on the cornea. Pug corneas tend to pigment easily with this sort of irritation. In the early stages, the pigment will be confined to the inner aspects of the cornea. If left untreated, the pigment commonly progresses across the cornea. It is not uncommon at all for the cornea to become completely pigmented if the underlying entropion remains. The damage to the cornea is called pigmentary keratitis and is a common cause of blindness in Pugs. It is much easier to prevent the pigment formation that to deal with it once it develops. Pugs with this type of entropion usually respond favorably to a procedure called medial canthoplasty. It involves narrowing of the eyelid opening with partial closure at the inner corner. The cosmetic result is not dramatic (once healed).