Entropion is the inward rolling of the eyelids. This results in direct contact between haired eyelid skin and the eye surface, which is irritating and uncomfortable. Entropion can involve one lid, or as many as all four eyelids. Some patients are mildly affected, demonstrating increased tearing and conjunctival redness. More severely affected patients will have chronic pain and vision threatening consequences including corneal inflammation (keratitis), scarring, pigmentation, and / or ulceration.
Primary (developmental) entropion
Primary (developmental) entropionis seen with higher prevalence is certain dog breeds, including English Bulldogs, Shar-Peis, Pugs, Golden and Labrador Retrievers, Chow Chows, and Rottweilers. Entropion is also occasionally seen in cats, most often secondary to chronic conjunctivitis or keratitis.
Primary entropion will typically develop in dogs by 18 – 24 months of age. Entropion that develops after 12 months of age, will most often require permanent surgical correction. When the condition develops in puppies or immature dogs, temporary correction with sutures (“eyelid tacking”) is recommended, as lid inversion may improve spontaneously with growth. If the entropion persists after the dog is fully grown, then surgery is needed for permanent correction. There are numerous surgical techniques to correct entropion, each tailored specifically to the cause, location and severity of the lid malformation.
Acquired (secondary) entropion
Acquired (secondary) entropion can develop is eyes following injury, chronic inflammation, and painful eye diseases. Eyelid spasms associated with eye pain results in “spastic entropion”. This form of entropion may also resolve with placement of temporary tacking sutures and medical management of the underlying painful eye disease(s). Surgical correction might be necessary, but the entropion will recur if the underlying cause goes untreated or uncontrolled. The success rates following entropion 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 that necessitate a second procedure, such as severe entropion with heavy facial skin and wrinkling, young patient, persistence or recurrence of underlying causes inciting the entropion.
Pugs commonly have entropion at the inner aspect of the lower eyelid (medial canthus). The haired skin at the medial canthus rub on the cornea, and Pug corneas tend to pigment easily with this type of irritation. If untreated, the pigment commonly progresses across the cornea and results in visual impairment. Complete corneal pigmentation, referred to as pigmentary keratitis, it is a common outcome when the underlying entropion remains. Pigmentary keratitis and is a common cause of blindness in Pugs. The condition is much easier to prevent, as much of the corneal pigment that is deposited in the cornea is permanent. 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 outcome is also good once the tissues have fully healed from surgery.
Entropion in cats most commonly results from a severe or chronic herpetic 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.