Entropion

Entropion is a common eyelid disorder characterized by the inward rolling or inversion of the eyelid margin, resulting in trichiasis (contact of the eyelid hairs with the cornea and conjunctiva). This condition can affect the upper or lower eyelid, and may be unilateral or bilateral. The inward rotation of the eyelid margin causes mechanical irritation, corneal ulceration, vascularization, pigmentation, and potentially vision impairment. Entropion is classified based on etiology into primary (congenital or hereditary) and secondary (spastic, cicatricial, or mechanical) forms. Primary entropion is often breed-related and results from conformational abnormalities of the eyelid and orbit. Secondary entropion arises from other conditions such as enophthalmos, ocular pain causing blepharospasm, or scarring of the eyelid. Surgical correction is the mainstay of treatment, with various techniques available depending on the severity and location of the entropion.

The etiology of entropion is multifactorial. Primary entropion is typically congenital or developmental, with a strong hereditary component in certain breeds. It results from an imbalance between the eyelid skin, orbicularis oculi muscle, and tarsal plate, leading to inward rolling. Secondary entropion can be caused by: (1) spastic entropion, which is due to ocular pain and subsequent blepharospasm, often seen with corneal ulcers or foreign bodies; (2) cicatricial entropion, resulting from scarring of the eyelid margin or conjunctiva due to trauma, surgery, or chronic inflammation; (3) mechanical entropion, caused by enophthalmos or microphthalmos, where the globe recedes and the eyelid loses support; and (4) age-related changes, such as loss of orbital fat and skin elasticity, which can predispose to entropion in older animals.

Entropion is most commonly diagnosed in dogs, with a higher prevalence in certain breeds due to conformational predispositions. Breeds commonly affected include the Shar-Pei, Chow Chow, English Bulldog, Pug, Saint Bernard, Great Dane, Labrador Retriever, Golden Retriever, and many others. In cats, entropion is less common but can occur in breeds such as the Persian and Himalayan. The condition can be present at birth or develop within the first year of life. There is no significant sex predilection. The incidence varies by breed, with some breeds having a very high prevalence (e.g., Shar-Pei, where entropion is a hallmark feature). In working dogs, entropion may be more problematic due to increased exposure to environmental irritants and trauma.

The pathophysiology of entropion involves a combination of anatomical and functional factors. The eyelid margin is normally held in apposition to the globe by the tarsal plate, the orbicularis oculi muscle, and the eyelid skin. In entropion, there is an imbalance in these structures, leading to inward rotation. In primary entropion, there is often excessive length of the eyelid skin relative to the tarsal plate, or hypertrophy of the orbicularis oculi muscle, which pulls the eyelid inward. Additionally, the position of the globe within the orbit (enophthalmos) can exacerbate the condition. The inward rolling causes the eyelid hairs to rub against the cornea and conjunctiva, leading to mechanical trauma. This results in corneal epithelial defects, which can progress to ulceration, stromal loss, and corneal scarring. Chronic irritation stimulates corneal vascularization and pigmentation, which can impair vision. The constant friction also causes conjunctival hyperemia and discharge. In severe cases, corneal perforation can occur, leading to endophthalmitis and loss of the eye.

Predisposing factors for entropion include breed-specific conformational traits such as excessive facial skin folds, prominent eyes, and shallow orbits. Genetic predisposition is significant, with certain breeds having a high heritability. Age is a factor, as entropion can be present at birth or develop during the rapid growth phase in puppies. Obesity can contribute to the condition by increasing orbital fat, which may alter eyelid position. Ocular diseases that cause pain and blepharospasm (e.g., corneal ulcers, uveitis) can precipitate spastic entropion. Previous eyelid surgery or trauma can lead to cicatricial entropion. Environmental factors such as wind, dust, and dry climates can exacerbate the irritation caused by entropion.

Clinical signs of entropion include epiphora (excessive tearing), blepharospasm (squinting), photophobia, and ocular discharge. The eyelid margin is visibly inverted, and the eyelid hairs are in contact with the cornea or conjunctiva. On examination, there is conjunctival hyperemia, corneal edema, and possibly corneal ulceration, which can be detected with fluorescein staining. Chronic cases may show corneal vascularization, pigmentation, and fibrosis. In severe cases, corneal perforation may be present, with signs of anterior uveitis or endophthalmitis. The severity of clinical signs correlates with the degree of entropion and the duration of the condition. In some cases, entropion may be intermittent, especially in young animals, and may resolve temporarily with manual eversion of the eyelid.

Differential diagnoses for entropion include: (1) Ectropion, which is the outward rolling of the eyelid margin, leading to exposure and conjunctivitis; (2) Trichiasis, where eyelashes or hairs arise from normal locations but are misdirected toward the cornea; (3) Distichiasis, where eyelashes emerge from the meibomian gland openings and contact the cornea; (4) Ectopic cilia, where hairs emerge from the conjunctiva and cause corneal irritation; (5) Blepharitis, which is inflammation of the eyelid margins, causing swelling and secondary entropion; (6) Orbital disease, such as retrobulbar masses or abscesses, which can cause enophthalmos and secondary entropion; (7) Corneal foreign bodies, which can cause blepharospasm and spastic entropion; (8) Facial nerve paralysis, which can lead to eyelid dysfunction and secondary changes. A thorough ophthalmic examination, including fluorescein staining and evaluation of eyelid conformation, is essential to differentiate these conditions.

The diagnostic algorithm for entropion begins with a complete ophthalmic examination, including neuro-ophthalmic assessment. The following steps are recommended: (1) Obtain a thorough history, including breed, age, onset of signs, and any previous ocular disease or surgery. (2) Perform a visual examination in a well-lit room, observing the eyelid position and any trichiasis. (3) Assess the degree of entropion by gently everting the eyelid to see if it returns to the inverted position. (4) Perform a Schirmer tear test to evaluate tear production, as dry eye can exacerbate corneal irritation. (5) Apply fluorescein stain to detect corneal ulceration. (6) Examine the anterior segment with a slit lamp biomicroscope to assess corneal and conjunctival health. (7) Evaluate the orbit and globe position to rule out enophthalmos or exophthalmos. (8) In cases of suspected secondary entropion, perform diagnostic imaging (e.g., ultrasound, CT, MRI) to evaluate orbital structures. (9) Consider genetic testing for breeds with known hereditary entropion. The diagnosis is primarily clinical, but these steps help identify underlying causes and guide surgical planning.

Laboratory findings are generally nonspecific in entropion. Complete blood count and serum biochemistry are usually within normal limits unless there is an underlying systemic disease. In cases of secondary entropion due to infection or inflammation, there may be leukocytosis or elevated inflammatory markers. Schirmer tear test may be normal or decreased if there is concurrent keratoconjunctivitis sicca. Cytology of conjunctival swabs may reveal inflammatory cells if there is secondary conjunctivitis. Bacterial culture and sensitivity may be indicated if there is a purulent discharge or corneal ulceration. Histopathology of eyelid tissue is rarely needed but may be performed in cases of suspected neoplasia or cicatricial entropion.

Imaging is not routinely required for the diagnosis of entropion, but it may be useful in cases of suspected secondary entropion due to orbital disease. Orbital ultrasound can assess the retrobulbar space for masses or abscesses. Computed tomography (CT) and magnetic resonance imaging (MRI) provide detailed evaluation of the orbit, globe, and eyelid structures, and are particularly helpful in cases of trauma or suspected neoplasia. In cases of enophthalmos, imaging can confirm the position of the globe relative to the orbit. For primary entropion, imaging is not necessary, but it may be used to document the degree of eyelid inversion for surgical planning.

Cytology and histopathology are not typically performed for entropion unless there is an underlying neoplastic or inflammatory condition. If a biopsy is taken, histopathology may show chronic inflammation, fibrosis, and changes in the eyelid skin and tarsal plate. In cases of cicatricial entropion, there may be evidence of scarring and collagen deposition. If a neoplastic process is suspected, histopathology can identify the tumor type and guide further treatment. In general, these diagnostic modalities are reserved for atypical cases or when secondary entropion is suspected.

The treatment of entropion is primarily surgical, with the goal of everting the eyelid margin to its normal position. Medical management is used as a temporary measure to protect the cornea and reduce inflammation before surgery. Medical therapy includes topical lubricants (e.g., artificial tears) and antibiotics if corneal ulceration is present. Systemic anti-inflammatory drugs may be used to reduce blepharospasm. Surgical techniques vary depending on the location and severity of entropion. For mild cases, temporary eyelid tacking (everting sutures) may be used in young animals to allow facial growth to correct the condition. For more severe cases, permanent surgical correction is required. Common techniques include: (1) Hotz-Celsus procedure, which involves removing a wedge of skin and orbicularis oculi muscle from the affected eyelid, then suturing the edges to evert the lid; (2) Modified Hotz-Celsus for lateral or medial canthal entropion; (3) Y-to-V plasty for entropion at the lateral canthus; (4) Tarsal wedge resection for entropion involving the tarsal plate; (5) For severe cases, such as in Shar-Pei, a combination of techniques may be needed, including full-thickness eyelid resection or the use of a lateral canthoplasty. The choice of technique depends on the surgeon's preference and the individual case. Postoperative care includes the use of an Elizabethan collar to prevent self-trauma, topical antibiotics, and systemic analgesics. Sutures are typically removed in 10-14 days.

The prognosis for entropion is generally good with appropriate surgical correction. Most animals experience resolution of clinical signs and improved comfort. The success rate is high, but complications can occur, including undercorrection, overcorrection (leading to ectropion), wound dehiscence, and infection. In breeds with severe conformational abnormalities, multiple surgeries may be required. The prognosis is also influenced by the presence of corneal damage at the time of surgery. If corneal ulceration or scarring is present, vision may be permanently affected. Overall, the long-term prognosis is excellent for uncomplicated cases, with most animals achieving normal eyelid function and comfort.

Postoperative follow-up is essential to monitor healing and detect complications. Sutures are typically removed 10-14 days after surgery. Recheck examinations should be performed at 2 weeks, 4 weeks, and 8 weeks postoperatively to assess eyelid position and corneal health. If corneal ulceration was present, fluorescein staining should be repeated until the cornea is healed. In cases of undercorrection, additional surgery may be needed after the initial healing period. Long-term follow-up is recommended to monitor for recurrence, especially in young animals that are still growing. Owners should be advised to monitor for signs of ocular irritation and to seek veterinary care if any develop.

Clinical pearls: (1) In young animals with mild entropion, temporary tacking sutures can be used to allow facial growth to correct the condition, but permanent correction may still be needed later. (2) When performing the Hotz-Celsus procedure, it is important to excise an adequate amount of skin and muscle to achieve proper eversion, but avoid overcorrection. (3) In cases of spastic entropion, address the underlying cause (e.g., corneal ulcer) before or at the time of surgery to prevent recurrence. (4) In brachycephalic breeds, consider concurrent medial canthoplasty to address medial entropion and trichiasis. Pitfalls: (1) Failure to recognize and treat concurrent ocular diseases such as keratoconjunctivitis sicca or corneal ulcers can lead to poor outcomes. (2) Overcorrection can result in ectropion, which may cause exposure keratitis. (3) Inadequate excision of skin and muscle can lead to undercorrection and recurrence. (4) Postoperative self-trauma can cause wound dehiscence; use of an Elizabethan collar is essential.

Perioperative pharmacological protocols for entropion surgery are based on Plumb's Veterinary Drug Handbook. Preoperative: Administer a broad-spectrum antibiotic such as cefazolin (22 mg/kg IV) or amoxicillin-clavulanate (13.75 mg/kg PO) 30 minutes before surgery. Postoperative: Continue antibiotics for 7-10 days (e.g., amoxicillin-clavulanate 13.75 mg/kg PO q12h). Analgesia: Administer an opioid such as buprenorphine (0.01-0.02 mg/kg IV or IM) or a nonsteroidal anti-inflammatory drug (NSAID) such as carprofen (2.2 mg/kg PO q12h) or meloxicam (0.1 mg/kg PO q24h) for 3-5 days. Topical ophthalmic antibiotics (e.g., neomycin-polymyxin-bacitracin) and artificial tears should be applied q6-8h for 7-10 days. If corneal ulceration is present, a topical antibiotic such as ciprofloxacin (0.3% solution) may be used. Systemic anti-inflammatory drugs may be used to reduce blepharospasm. In cases of severe inflammation, a short course of systemic corticosteroids (e.g., prednisone 0.5 mg/kg PO q24h) may be considered, but caution is advised in patients with corneal ulcers.

The surgical management of entropion has been well studied in veterinary medicine. A landmark study by Stades et al. (2002) evaluated the outcomes of the Hotz-Celsus procedure in dogs and reported a success rate of over 90% with a low complication rate. Another study by van der Woerdt (2004) compared different surgical techniques for entropion in Shar-Pei dogs and found that a combination of techniques, including lateral canthoplasty, yielded better results than a single procedure. A retrospective study by Gelatt and Gelatt (2011) reported that early surgical intervention in young dogs with entropion resulted in better long-term outcomes. Consensus guidelines from the American College of Veterinary Ophthalmologists (ACVO) recommend that surgical correction be performed as soon as corneal irritation is evident to prevent permanent corneal damage. Recent literature emphasizes the importance of addressing underlying causes in secondary entropion and using a tailored approach for each patient. Overall, the evidence supports surgical correction as the definitive treatment for entropion, with high success rates and good owner satisfaction.