Entropion

What it is

Entropion is the inversion of all or part of the eyelid margin toward the eye. The hairs of the eyelid skin then rub on the cornea and conjunctiva (trichiasis), causing pain, chronic irritation and corneal damage. Three forms are recognised:

• Conformational (developmental): inherited and related to the shape of the skull, the size of the palpebral fissure, the depth of the orbit and excess facial skin. The most common form in the dog.
• Spastic: caused by blepharospasm secondary to another painful eye disease, which pulls the lid inward; it can then perpetuate itself.
• Cicatricial: caused by scarring of the eyelid after trauma or surgery.

Who it affects

Conformational entropion appears in puppies and young dogs of predisposed breeds: shar-pei (in which it may appear in the first weeks of life), chow chow, English bulldog, Rottweiler, Saint Bernard, mastiffs, Labrador and golden retriever, spaniels, and others. Giant breeds with large palpebral fissures may have combined entropion and ectropion ("diamond eye").

Anatomy involved

Each eyelid (palpebra) is a fold of skin lined inside by palpebral conjunctiva. It contains the orbicularis oculi muscle, a weak fibrous tarsus and the tarsal glands, which open at the margin and supply the lipid layer of the tear film. In the dog only the upper lid carries true eyelashes (cilia). Entropion most often affects the lateral part of the lower lid; in breeds with heavy facial folds, such as the shar-pei and chow chow, the upper lid is frequently involved too.

Clinical signs

Epiphora, blepharospasm, ocular discharge, conjunctival hyperaemia and rubbing of the eye. Chronic cases show keratitis with corneal vascularisation and pigmentation; corneal ulcers are common. The rolled-in lid margin is often visible, with the hairs touching the eye.

Diagnosis

• Examination of the eyelids in the awake dog, before sedation or topical anaesthesia, which change lid position.
• Application of a topical anaesthetic: if the entropion disappears, a spastic component is present.
• Fluorescein to look for corneal ulcers, and examination for other causes of pain (distichiasis, ectopic cilia, keratoconjunctivitis sicca).

Treatment

In puppies, temporary eyelid tacking sutures evert the lid until the head grows, and may avoid definitive surgery. In adults, or when tacking fails, a Hotz-Celsus procedure or one of its modifications removes a strip of skin and orbicularis muscle parallel to the margin to evert it; in giant breeds, shortening of the palpebral fissure may also be needed. Overcorrection must be avoided because it produces ectropion. Spastic entropion is treated by removing the cause of pain. Because the conformational form is heritable, affected dogs should not be used for breeding.

In the cat

Entropion is less common in the cat than in the dog. Several situations are recognised:

• Brachycephalic breeds (Persian, Exotic, Himalayan): entropion of the medial canthus of the lower lid, often combined with nasal folds touching the cornea.
• Young cats of some breeds, such as the Maine Coon: entropion of the lateral lower lid.
• Spastic entropion secondary to painful corneal disease, frequently feline herpesvirus keratitis; blepharospasm keeps the lid rolled in and the rubbing hair perpetuates the corneal damage.
• Older cats: enophthalmos from loss of orbital fat or weight loss leaves the lid unsupported and encourages it to roll in.

Besides correcting the lid (Hotz-Celsus procedure or its variants, canthoplasties in brachycephalic cats), the underlying eye disease must be treated; cats with chronic entropion are at risk of corneal sequestrum.

Key studies in the cat

• Williams and Kim (2009), 50 cats with entropion at a referral clinic. Sixteen were young (mean 4.1 years) with prior irritative surface disease such as conjunctivitis, ulcers or sequestrum; 26 were older (mean 11.3 years) with involutional entropion with or without enophthalmos; 5 were Persians and 3 young intact male Maine Coons. One Hotz-Celsus procedure cured most cats, although more eyelid tissue had to be removed than in the dog.
• White et al. (2012), 124 cats (200 eyes) operated on for lower eyelid entropion. A single procedure corrected 96% of eyes, and Hotz-Celsus combined with lateral canthal closure succeeded in 99.2%. In geriatric cats, 37% had a corneal sequestrum at the same time, and 17% of cats with unilateral entropion developed it later in the other eye if that eye was not operated on prophylactically.
• Anagrius et al. (2021), examination of 64 Persian and 12 Exotic Shorthair show cats compared with 20 non-pedigree cats. Entropion was found in 32% of the Persians and Exotics, together with stenotic nares (86%) and epiphora (83%); these findings were not common in the non-pedigree cats.
• Frejlich and Payen (2026), 392 cats with ulcerative keratitis or corneal sequestrum. Entropion of the lateral lower lid accompanied these lesions more often in non-brachycephalic cats: 38 of 286 of their eyes needed entropion surgery, compared with 3 of 128 eyes of brachycephalic cats.