Entropion

TL;DR. Entropion is a common, painful condition where a dog's or cat's eyelids roll inward, causing hair to rub against the eye; while it can lead to severe corneal damage and vision loss if left untreated, it is highly correctable with surgery.

Entropion causes the eyelid margin to roll inward, bringing irritating facial hair into direct contact with the eye.

What is it?

Entropion is a common ophthalmic condition in veterinary medicine where the margins of the eyelid roll inward toward the eyeball. This abnormal positioning causes the eyelashes, or the normal facial hair surrounding the eye, to rub continuously against the sensitive surfaces of the eye—specifically the cornea (the clear front window of the eye) and the conjunctiva (the pink membrane lining the inside of the eyelids).

To understand entropion, it helps to understand basic eyelid anatomy. The opening between the eyelids is called the palpebral fissure. The structural stiffness of the eyelid is maintained by a thin layer of dense connective tissue called the tarsal plate. When there is a mismatch between the length of the eyelid and the size of the eyeball, or if the tarsal plate lacks sufficient stiffness, the eyelid can lose its structural support and roll inward.

Veterinarians classify entropion based on its location and its underlying cause:

• Medial canthal entropion: The inward rolling occurs at the inner corner of the eye, near the nose.
• Lateral canthal entropion: The inward rolling occurs at the outer corner of the eye.
• Upper or lower eyelid entropion: The condition can affect the top lid, the bottom lid, or both.
• Conformational entropion: A structural, often genetic defect in the shape of the face, skull, or eyelids.
• Spastic entropion: A temporary or permanent inward rolling triggered by severe eye pain and squinting.

As noted in a leading veterinary surgical textbook:

"In adult dogs, spastic entropion may be seen in animals that have a painful ocular condition leading to excessive blepharospasm similar to that described for cats. Lower eyelid entropion in dogs is commonly seen in younger dogs (less than one year of age) due to deep-set globes and conformational defects of the eyelids and facial structures. Lower eyelid entropion may also have a spastic component"

This anatomical cross-section of a canine eye illustrates how the rolled-in lid margin allows hair to scrape the cornea.

Causes & risk factors

The primary cause of conformational entropion is genetic. It is highly linked to specific facial structures, such as the flat faces of brachycephalic breeds, the heavy, loose skin of giant breeds, or deep-set eyes. In these animals, the physical relationship between the eyeball (globe) and the surrounding bony socket (orbit) is disproportionate, leaving the eyelid margins without adequate physical support.

In contrast, spastic entropion is caused by an active cycle of pain. When an animal experiences an initial eye injury or irritation (such as a foreign body, scratch, or infection), they squint intensely. This involuntary squinting is called blepharospasm. The constant, forceful contraction of the muscles around the eye pulls the eyelid inward. Once the eyelid rolls inward, the facial hair begins to rub against the eye, causing even more pain and more squinting. This creates a self-perpetuating cycle of irritation and spasm.

Age is also a significant risk factor. Young dogs under one year of age frequently develop lower eyelid entropion as their skull structures grow and change. In older animals, age-related loss of muscle tone around the orbit or loss of fat behind the eye can cause the eyeball to sink slightly backward, secondary to which the eyelids roll inward.

Signs to watch for

The clinical signs of entropion are directly related to the physical trauma of hair rubbing against the delicate structures of the eye. According to a standard veterinary reference:

"The condition is commonly seen in dogs and occasionally in cats resulting in frictional irritation of the conjunctival and corneal surfaces by eyelashes and/or facial hairs of the lid. This frictional irritation is painful and may lead to corneal ulceration, corneal neovascularization and deposition of pigment on the corneal surface (pigmentary keratitis). In severe cases, vision loss from corneal"

You should watch for the following symptoms in your pet:

• Frictional irritation of the conjunctival and corneal surfaces (Cardinal): The constant physical rubbing of hair against the eye, leading to redness and irritation.
• Blepharospasm (Common): Squinting, blinking excessively, or holding the eye tightly shut due to pain.
• Pain (Common): Pawing at the face, rubbing the eye against furniture or carpet, and general sensitivity around the head.
• Corneal ulceration (Common): Scratches or open sores on the clear surface of the eye caused by the abrasive action of the hair.
• Corneal neovascularization (Common): The growth of tiny, red blood vessels across the normally clear cornea as the eye attempts to heal itself.
• Pigmentary keratitis (Common): The deposition of dark brown or black pigment on the corneal surface, which acts like a scar and blocks light.
• Corneal scarring (Occasional): Cloudy, white, or opaque patches on the cornea that persist after active inflammation subsides.
• Vision loss (Rare): Progressive blindness caused by extensive scarring, pigment deposition, or severe ulceration.
• Corneal perforation (Rare): A deep ulcer that wears completely through the cornea, causing the fluid inside the eye to leak out.
• Loss of the globe (Rare): Surgical removal of the eye (enucleation) required if a perforated eye becomes severely infected or collapses.

Squinting (blepharospasm) and excessive tearing are common signs of the pain caused by entropion.

How vets diagnose it

Diagnosing entropion requires a systematic approach by your veterinarian. The first step is a thorough preoperative examination with magnification. Your vet will use specialized magnifying loupes or a slit lamp biomicroscope to closely examine the eyelid margins, the direction of hair growth, and the health of the cornea. This examination must be performed while the animal is fully awake and conscious, as anesthesia or heavy sedation can relax the facial muscles and temporarily mask the abnormal rolling of the eyelids.

A critical diagnostic step is differentiating between permanent conformational entropion and temporary spastic entropion. To do this, your veterinarian will perform a topical anesthetic application test.

Applying a topical anesthetic drop helps veterinarians determine if the entropion has a temporary spastic component.

As detailed in veterinary surgical literature:

"A simple technique to evaluate for spastic entropion is to apply a drop of topical anesthetic (0. 5% proparacaine) to determine if blepharospasm abates. If topical anesthetic use relaxes the blepharospasm and resulting entropion, a temporary everting technique maintained for 7-10 days may result in resolution of the entropion without tissue excision."

By applying a local ophthalmic anesthetic, such as proxymetacaine or proparacaine, your vet temporarily numbs the surface of the eye. If the inward rolling of the eyelid was purely a spastic reaction to pain, the eyelid will return to its normal position once the pain is blocked. If the eyelid remains rolled inward even after the eye is completely numbed, the diagnosis is conformational entropion, which typically requires structural surgical correction.

Additionally, your vet will perform a fluorescein stain test. This involves placing a small amount of green fluorescent dye into the eye to check for corneal ulcers. Any area where the protective outer layer of the cornea has been scraped away by rubbing hairs will glow bright green under a blue light.

Treatment options

The treatment strategy for entropion depends heavily on the animal's age, the underlying cause (conformational vs. spastic), and the severity of the condition.

Medical Management

Medical therapy is primarily used as a supportive measure or temporary fix.

• Local Ophthalmic Anesthetics: Medications like proxymetacaine are used during diagnostic evaluations but are not suitable for long-term home treatment because they delay corneal healing and can be toxic to the cornea with repeated use.
• Anticholinergics / Parasympatholytics: Topical atropine drops or ointment may be prescribed. Atropine dilates the pupil and relaxes the painful spasms of the ciliary muscle inside the eye, providing significant pain relief.
• Lubricants and Antibiotics: Broad-spectrum topical antibiotic ointments are frequently used to treat or prevent secondary bacterial infections in corneal ulcers, while artificial tear ointments provide a physical barrier to reduce friction.

Temporary Surgical Techniques (Tacking)

In young, growing puppies (typically under six months of age), permanent surgical removal of eyelid tissue is avoided because the skull shape is still changing. Instead, your vet will perform a temporary everting suture technique, commonly called "eyelid tacking." Using temporary sutures or surgical staples, the vet rolls the eyelid outward and secures it in a normal position. These sutures are left in place for 7 to 10 days (and sometimes replaced as the puppy grows) to allow the facial structures to mature without the eyelashes damaging the cornea.

Permanent Surgical Correction

For adult animals with conformational entropion, permanent surgery is the gold standard. The primary goal is to return the eyelid margin to its normal anatomical position.

• Hotz-Celsus Technique: This is the most common surgical procedure. The surgeon removes a precise, crescent-shaped strip of skin and muscle from just below (or above) the affected eyelid margin. When the edges of the incision are sutured back together, the tension pulls the rolled-in eyelid outward into a normal alignment.
• Arrowhead Technique: Used primarily for lateral canthal entropion (outer corner), this technique involves removing an arrowhead-shaped piece of skin near the outer corner of the eye to stabilize and pull the eyelid outward.
• Combination Procedures: In giant breeds with complex eyelid deformities, surgeons may combine entropion correction with procedures to shorten excessively long eyelids.

After surgery, your pet must wear an Elizabethan collar (E-collar) at all times to prevent them from rubbing or scratching at the sutures. Your vet will typically remove the sutures 10 to 14 days after the procedure.

A major surgical risk is overcorrection. If the surgeon removes too much skin, the eyelid will roll outward (a condition called ectropion), which can lead to dry eyes and exposure keratitis. Therefore, vets often prefer to perform a conservative correction, knowing they can perform a minor revision later if needed.

Prognosis

The prognosis for pets with entropion is generally excellent, provided they receive timely and appropriate veterinary care. Once surgical correction is successfully performed, the physical irritation stops, corneal ulcers heal, and the pet experiences immediate relief from chronic pain.

However, if the condition is left untreated, the prognosis for maintaining vision is guarded. Chronic friction leads to severe corneal scarring, pigmentary keratitis, and potentially corneal perforation, which can result in permanent blindness or the loss of the eye.

Prevention

Because conformational entropion is an inherited, congenital defect, there are no lifestyle changes or preventative measures that can stop it from developing in an individual animal.

Prevention relies entirely on responsible breeding practices. Animals diagnosed with conformational entropion should not be used for breeding, as they can pass the genetic predisposition for abnormal eyelid and skull structures to their offspring. Early screening of litters by a veterinary ophthalmologist can help identify affected puppies early, allowing for timely intervention before permanent corneal damage occurs.

When to call your vet

Eye conditions can deteriorate rapidly. You should contact your veterinarian immediately if you notice any signs of ocular discomfort.

Seek emergency veterinary care if you observe any of the following red flags:

• Your pet is holding their eye completely closed or squinting severely.
• You notice a cloudy, blue, or white film developing over the clear part of the eye.
• There is thick green or yellow discharge draining from the eye.
• Your pet is actively pawing or rubbing at their eye, which can quickly cause a corneal perforation.
• The eye appears visibly swollen, bloodshot, or bulging.

For specific breeds

Different breeds experience entropion in distinct anatomical patterns due to their unique skull shapes and facial skin folds:

• Brachycephalic Breeds (Pugs, Shih Tzus, Lhasa Apsos, Persians, Himalayans): These flat-faced breeds are highly predisposed to medial canthal entropion. Because of their short noses and prominent eyes, the inner corners of their eyelids roll inward, causing the facial hair near the nose to rub constantly against the cornea.
• Giant and Mastiff-type Breeds (Mastiffs, Bernese Mountain Dogs, Newfoundlands, St. Bernards, Bloodhounds): These breeds often present with a complex combination of eyelid issues. As noted in surgical texts:

"Bernard, mastiffs, Bernese mountain dogs, Newfoundlands, and others) with excessively long palpebral fissures (macropalpebral fissure) and lax tarsal plates, a combination of lateral canthal entropion and lower lid ectropion with an upward "notching" of the upper eyelid margin is seen. Medial canthal entropion is seen primarily in brachycephalic breeds (pugs, Shi Tzus, Lhasa Apsos, and others). Th"

• Breeds with Excessive Skin Folds (Chinese Shar-Peis, Chow Chows, English Bulldogs): These breeds frequently suffer from severe, multi-quadrant entropion affecting both the upper and lower eyelids. The heavy skin folds on their foreheads and faces push the eyelids downward and inward, often requiring complex surgical reconstructions and facelift-style procedures to relieve the pressure on their eyes.

Sources

• Current Techniques in Small Animal Surgery, 5th Edition, pp. 167-168.

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