Entropion, in contrast to ectropion discussed Monday, is an in-rolling of the eyelids.
Here, the poster child is the Chinese Shar pei, a breed of dog in which the condition is so rampant that virtually every puppy needs a temporary technique for all four lids when young, and definitive surgical correction as a young adult. Among cats, the Persian (and other flat-faced breeds) have the greatest incidence of congenital entropion.
Entropion is a problem because the haired skin of the face/eyelid is turned inward, coming into direct contact with the cornea, the clear part of the eye. The result is similar to rubbing one’s eye with a shoebrush. While your eyelids are open.
Immediately the globe (eyeball) begins to react with increased tear flow in a vain attempt to wash out the irritant. Simultaneously blood flow is increased to outer structures of the globe, sending an increased number of healing and cleaning cells, along with protective antibodies.
If entropion is allowed to persist, the cornea becomes cloudy, as in the photo, interfering with vision.
With ongoing irritation the body begins to instill protective black pigment into the formerly-clear cornea. When the entire cornea is blacked over, the patient is blind.
Like ectropion, there are multiple possible causes for entropion.
Congenital entropion exists from or soon after birth. Usually it is an inherited condition common in the breed, such as Shar pei, Chow-Chow, Rottweiler, various mastiffs, Great Dane, St. Bernard and Cocker Spaniel.
Acquired entropion occurs secondary to another condition, usually one that causes blepharospasm. Blepharospasm is any condition that causes irregular muscle contraction in the eyelids, from the Greek prefix blephara, meaning “eyelids” (singular is blepharon) plus “spasm.” Any inflammatory process that causes pain in the eye can lead to spasmodic contraction of eyelid muscles which, in turn, can roll the outer aspect of the eyelids into the globe.
Cicatricial entropion occurs when scarring of the lids results in an in-rolling. Such scarring might result from a wound in which one dog bites another in the face.
Iatrogenic entropion is usually a result of a surgical procedure called blepharoplasty. “Iatrogenic” refers to damage caused by a doctor. For example, if a veterinarian is seeking to repair the condition known as ectropion, which is an out-rolling of the eyelids, he could perform certain techniques that would over-correct and roll the eyelids inward.
If your pet is diagnosed with entropion, just imagine yourself living with that shoebrush rubbing your cornea every time you blink. Do that, and you’ll have a pretty good idea of what your dog or cat is going through and why your pet’s doctor is so strongly encouraging you to have his eyelid(s) surgically repaired.
When performing entropion surgery it is not unusual for veterinarians to over-correct slightly, even producing a mild ectropion. Sometimes a patient may even require a second surgery. This occurs when we perform a correction conservatively and find that additional tissue removal is required to accurately place the lid margin in contact with the globe.