Canine Eyelid Diseases—Entropion

Entropion, the inward turning of the eyelid margin, is a common canine ophthalmic condition causing significant discomfort and potential vision impairment. This condition involves the partial or complete inversion of the eyelid edge, resulting in the irritating contact of eyelashes and hairs against the conjunctiva and cornea. While aesthetically unappealing, the consequences of untreated entropion can be severe, leading to chronic inflammation, corneal ulceration, and even vision loss. Understanding the causes, symptoms, and treatment options is crucial for responsible pet ownership.

I. Etiology of Canine Entropion:

The causes of entropion are multifaceted, broadly categorized into developmental, spasmodic, and acquired forms.

1. Developmental Entropion: This is frequently linked to breed predisposition and inherited genetic defects influencing facial and ocular structure. Certain breeds exhibit a higher incidence, notably Shar-Peis, Chow Chows, Saint Bernards, Labrador Retrievers, Great Danes, and small breeds like toy Poodles. The degree of eyelid inversion varies; in some cases, the entire eyelid may be affected (often seen in Shar-Peis), while others present with only medial lower eyelid entropion (more common in smaller breeds). The underlying genetic mechanisms remain incompletely understood, though a simple dominant inheritance pattern is suspected, making accurate prediction challenging. The depth and size of the eye socket also play a role; for instance, Great Danes, with their large, deep sockets, may lack sufficient support for the eyelids, contributing to entropion.

2. Spasmodic Entropion: This secondary form arises from irritation and inflammation stimulating eyelid muscle spasm. Underlying conditions like conjunctivitis, keratoconjunctivitis sicca (dry eye), corneal ulcers, foreign bodies, distichiasis (double row of eyelashes), or trichiasis (misdirected eyelashes) can trigger this type of entropion. The irritation leads to blepharospasm (involuntary eyelid closure), which, over time, can contribute to and exacerbate the inward turning. This form often affects only one eye and can occur at any age. Pain and discomfort are common symptoms alongside the inward turning of the eyelid.

3. Acquired Entropion: This form develops later in life, often due to progressive changes in the underlying tissues. Loss of orbital fat, muscle atrophy (particularly the malar muscle), or decreased skin elasticity associated with aging can cause the eyelid to lose its normal support and turn inward. This is more common in older dogs.

II. Clinical Presentation:

The clinical signs of entropion vary with the severity. Mild cases may only show slight irritation, excessive tearing (epiphora), and occasional mild discomfort as the eyelashes gently brush against the ocular surface. However, more severe cases present with significant symptoms:

Unilateral or bilateral eyelid inversion: Entropion can affect one or both eyes, and either the upper or lower eyelids (or both).

Ocular irritation: Constant rubbing of the eyelashes and hairs on the cornea and conjunctiva causes significant irritation, leading to redness (conjunctival hyperemia), discomfort, and excessive tearing.

Squinting (blepharospasm): The dog may try to protect its eyes by squinting or partially closing them.

Pain: Severe cases can be painful, causing the dog to show signs of discomfort or avoid bright light (photophobia).

Conjunctivitis and Keratitis: Chronic irritation can lead to secondary infections, including conjunctivitis (inflammation of the conjunctiva) and keratitis (inflammation of the cornea). These conditions manifest as redness, swelling, discharge, and potentially corneal ulceration or clouding. In advanced cases, corneal scarring and vision loss can result.

III. Treatment Modalities:

Treatment approaches for entropion depend on the cause and severity of the condition:

1. Developmental Entropion: Surgical correction is typically the most effective treatment. However, timing is crucial; waiting until the dog is 4-6 months old, or when facial features have fully matured, allows for a more predictable outcome. For breeds like Shar-Peis, temporary eyelid sutures may be performed as early as 3 weeks of age to prevent severe corneal damage before definitive surgical correction.

2. Spasmodic Entropion: Addressing the underlying cause is paramount. Treating conjunctivitis, removing foreign bodies, or managing dry eye can resolve the spasm and the entropion. In the interim, temporary measures like soft contact lenses or temporary eyelid sutures can provide relief from the irritation. If these conservative methods fail, surgical correction (entropion repair) becomes necessary.

3. Acquired Entropion: Surgical procedures, such as lateral canthoplasty (a procedure that tightens the lateral canthus, the outer corner of the eye), are often employed to reduce the palpebral fissure (eyelid opening) and correct the inward turning. This may involve creating and repositioning skin flaps in the lateral eyelid region.

IV. Surgical Techniques:

Several surgical techniques exist for entropion correction, each tailored to the specific anatomy and severity of the case. These include wedge resection, full-thickness resection, and lateral canthoplasty, among others. The choice of technique depends on the surgeon’s experience and the individual needs of the patient. Post-operative care typically includes the use of an Elizabethan collar (cone) to prevent the dog from scratching or rubbing the eyes, and topical antibiotic and anti-inflammatory medications to minimize infection and discomfort. Regular follow-up veterinary examinations are essential to monitor healing and address any complications.

V. Prognosis:

With appropriate and timely intervention, the prognosis for most cases of entropion is generally good. Surgical correction is often successful in restoring normal eyelid position and alleviating symptoms. However, the long-term outcome depends on the severity of the underlying condition, the dog’s overall health, and adherence to post-operative care instructions. Early detection and treatment are key to minimizing the risk of complications and preserving the dog’s vision. Regular veterinary check-ups, especially for breeds predisposed to entropion, are highly recommended.