Entropion – An Overview

Introduction (what is entropion?)

Entropion is a common, multifactorial eye condition in both dogs and cats. Entropion occurs when the eyelid rolls inward, causing the eyelashes or hair of the lid to rub against the surface of the eye (the cornea). The opposite of entropion is ectropion which causes the eyelid margin to fall or droop away from the cornea [FIG 2]. Entropion can result in irritation, discomfort, and potential damage to the cornea. Typically, entropion is classified as primary, secondary, spastic, or cicatricial.

Most commonly the lower lid, and especially the lower outer portion of the lid, is affected. This is called lower lateral entropion [FIG 3]. In contrast, entropion of the lower eyelid closest to the nose is called medial canthal entropion [FIG 4]. Medial canthal entropion (especially of the inside corner of the lower lid) is a common cause of excessive tearing in brachycephalic dogs, such as Pugs, and Shih Tzus, and also cats, such as Burmese, Himalayan, and Persian, and also in canine breeds with “tight” eyelid confirmation (e.g. Toy and Miniature Poodles, Bichon Frise, and Maltese).

Entropion in this location is often subtle and frequently overlooked as a cause of tearing and/or corneal pigmentation. Many brachycephalic breeds also have excessive nasal folds, which can exacerbate the amount of entropion in this location. Longer eyelid length or eyelid opening (macroblepharon) has also been identified as a risk factor for primary entropion in both dogs and cats. In giant breeds with severe macroblepharon, such as the St. Bernard and Mastiff, a combination of entropion and ectropion (rolling out of the eyelid margin) is commonly seen and is colloquially referred to as “diamond eye” or “pagoda lids” because of the diamond-shaped appearance of the eyelids [FIG 5].

Causes of entropion

Typically, entropion is classified as primary, secondary, spastic, or cicatricial.

1. Primary entropion is most commonly caused by anatomic or developmental abnormalities of the eyelid and may be seen at birth or up to several months of age as bones of the head and face and associated facial skin gain their adult conformation. This is especially true for breeds with a large amount of skin around their eyes, or giant breeds who may not mature until they are older than 1 year of age.

Breeds such as Chow Chows, Bulldogs, Rottweilers, Shar-pei, Labrador retrievers, and brachycephalic breeds (short-nosed breeds) such as Pugs are most susceptible to entropion due to facial structure and genetic predisposition. A genetic component has been suggested but not definitely established. The condition is likely to be inherited as a polygenic trait (i.e. multiple genes interplay to result in entropion) such that it is strongly recommended that affected animals are not bred.

Primary entropion is uncommon in cats and is most commonly reported in the Persian and Maine Coon breeds. In general, primary entropion is more common in dogs than in cats.

2. Secondary entropion, like primary entropion, occurs from conformational changes, however secondary entropion occurs due to a change in the position and/or size of the globe (the eye), rather than to lid or skin development. The eyelids naturally rest on the surface of the eye.

If the eye is recessed, that is, the eye sits deeper within the bony socket of the skull, for whatever reason, the eyelids lose their support and fall inwards, closer to the eye. Globe recession can be changed by age-related loss of the normally plump orbital fat pad present behind the globe, retraction of the globe into the bony socket (enophthalmia) as in neurologic disturbance (eg Horner’s syndrome), or shrinkage of the globe (phthisis bulbi).

In general, secondary entropion in cats most commonly occurs in the lower lid whereas in dogs, secondary entropion more commonly occurs in the upper eyelid and is also associated with upper eyelid laxity (ptosis).

2. Spastic entropion is caused by squinting (blepharospasm) that occurs in response to any painful condition affecting the eye. Irritation is almost always to the cornea and is most commonly caused by abnormal hairs, keratitis, uveitis, and dry eye which can all result in painful corneal ulcers.
Primary entropion and spastic entropion can be difficult to differentiate clinically and quite often the spastic component will worsen the primary component.

The spastic component of entropion can be identified by the change in eyelid position noted following application of a topical anaesthetic to the cornea: any degree of entropion that persists after the pain sensation has been removed by the anaesthetic can be concluded to be the primary component.

A tricky conundrum can be raised….just as pain causes squinting and subsequent entropion, so too can primary entropion cause corneal pain and subsequent squinting. We are left asking which came first? While not always clear cut, examination of the history for clues of the presence of entropion before becoming painful, underlying corneal changes consistent with a painful process, or the presence of physical abnormalities such as extra eyelashes that can cause corneal irritation, can help to unravel this mystery.

When a purely spastic entropion is identified (that is, all the entropion is resolved following application of a cornea anesthetic), surgery to correct the entropion is not recommended. Instead, placement of tacking sutures [FIG 6] to temporarily roll out the offending lid(s) and correction of the underlying irritant (corneal ulceration, keratitis, removal of abnormal hairs, etc) is recommended.

3. Cicatricial entropion is entropion caused by contracted scar tissue in the eyelid; it is uncommon and is caused by poor healing of eyelid injury (such as laceration), poor outcome of eyelid surgery, or chronic inflammation and subsequent scarring and contraction of eyelid tissue. In cats, it has been hypothesized that cicatricial entropion may eventually develop after long-term spastic entropion.

How do I know if my pet has entropion?

The signs of entropion in both dogs and cats include tearing, squinting, and visible rolling inward of the eyelid. The signs can be obvious and constant, or subtle and intermittent. If left untreated, entropion can lead to corneal ulcers, infections, and permanent vision loss. Animals are often noted to be rubbing at the affected eye, and this in turn can cause additional problems such as corneal ulceration. There are no genetic tests available for entropion.

How is entropion diagnosed?

Your veterinarian might be able to diagnose entropion from the history of changes noted by you, but also by physically examining the eyelids. However, sometimes referral to a veterinary ophthalmologist is needed for correct diagnosis, especially in patients with subtle and intermittent signs. After completing a thorough eye examination to rule out any underlying conditions that might also cause the changes you have noticed, your veterinarian will examine the eyelids more closely using magnification.

The lids will be examined for the presence of abnormal hairs, presence of scarring or other signs of disease, and then manipulated to determine the shape, tightness, and laxity of the lids, and degree of rolling-in of the eyelid margin. After determining the type of entropion that is present, a plan to resolve the changes noted will be tailored for your pet. There is no one-size-fits-all plan for entropion as the requirements of one dog will differ from another.

Treatment for entropion

When entropion occurs in a young animal [i.e. prior to mature facial conformation], or in cases of spastic entropion, temporary “tacking sutures” can be placed to evert the eyelid margins [FIG 6]. Several temporary stitches, known as vertical mattress sutures, are carefully placed approximately 3 millimetres from the eyelid margin and opposed to the skin overlying the bony orbital margin.

Placement of tacking sutures often eliminates the need for, or reduces the extent of, surgical correction (i.e. plastic surgery, or blepharoplasty) later in life. Tissue adhesives and skin staples have also been used to tack eyelids. Some puppies require multiple tacking procedures, typically every 2-4 weeks, until they are old enough for surgical correction. Once mature facial conformation is attained, surgical correction is required if entropion persists after the tacking sutures are removed.

It should be noted that some puppies with extreme entropion (for example Shar Pei’s), require surgical correction before they are fully grown and that additional correction may be needed when full growth has been achieved.
If surgery is required and until surgery can be performed, application of a thick corneal lubricant is recommended to provide a barrier between the sensitive cornea and the hair of the rolled in eyelids. Ointments are best, rather than gels as they are thicker to provide more protection. This will help to reduce the potential for corneal damage and scarring.

When a patient is fully grown (or very nearly fully grown), entropion surgery for permanent correction of entropion can be performed. Surgical correction has been reported as the only definitive treatment for entropion. There are many surgical techniques available to correct entropion, and your veterinarian or veterinary ophthalmologist will choose the best procedure for your pet based on the cause, size, and location of the entropion. Plastic surgery is an art form, and no two patients are alike in how their lids will be reconstructed. It is critical to understand that more than one surgery may be needed to adequately correct the problem.

Use of an E-collar following surgery is mandatory as stitches can become itchy and are often scratched out before healing has been completed. In this event, surgery is often required again but the cosmetic outcome is never as good as it would have been with proper healing the first time.

In some cases of secondary entropion or small areas of cicatricial entropion, subdermal filler can be injected into the eyelid margin to plump and roll-out the lid margin. While not permanent, this technique has been used most commonly in elderly cats with entropion caused by loss of orbital fat behind the eye, and in cats born without an upper outer eyelid margin (eyelid agenesis).

Prevention of entropion

Prevention of entropion in pets involves careful breeding practices to reduce the incidence of genetic factors that contribute to the condition. Regular veterinary check-ups can also help detect entropion early before it becomes severe.