2.16 Diseases of the Eyelids and Conjunctiva

What are the main functions of the eyelid?

Protect the eye, produce and distribute tears, aid tear drainage, help control light entering the eye.

What are congenital disorders of the eyelids?

• Entropion

• Ankyloplephron

• Dermoid

• Agenesis

• Coloboma

What is entropion?

Inward rolling of the eyelid margin, commonly seen in foals.

What causes entropion in foals and adults?

In foals, due to dehydration or congenital disorders; in adults, after trauma.

What is the pathology of entropion?

The turning of the eyelid edge causes eyelashes to rub against the eye, irritating the conjunctiva and cornea.

What are the long-term effects of untreated entropion?

Scarring, abnormal coloring, and slow-healing sores.

What are the clinical signs of entropion?

Epiphora (excessive tearing), blepharospasm (blinking), conjunctivitis, and keratitis.

How is entropion treated?

Temporary repair with vertical mattress suture, subconjunctival injections, or surgery if necessary in adulthood (blepharoplasty).

What is ankyloblephron?

The failure of eyelids to open after birth.

What is a dermoid?

Focal congenital mass of displaced skin and tissue, sometimes including hair, that may need surgical removal if irritating.

What is coloboma?

Full thickness absence of portions of the normal eyelid, requiring reconstructive blepharoplasty if ocular disease is present.

What is agenesis of the eyelid?

Complete absence of the eyelid, requiring reconstructive blepharoplasty if ocular disease is present.

What are acquired eyelid disorders?

• Trauma/lacerations

• Ectropion

• Blepharitis

• Neoplasia

• Distichiasis

• Trichiasis

• Prominence of the nictating membrane

What should be done for eyelid trauma or lacerations?

Treat immediately to avoid further eye damage with conservative or surgical methods.

How is trauma to the eyelids treated?

• Conservative: topical compress, topical ATB, systemic NSAIDS.

• Surgical: temporary tarsorrhaphy, re-apposition of eyelid margin. NEVER RESECT/ CUT OFF eyelid laceration!

What is ectropion?

Eversion of the eyelid margin, often due to complications from eyelid trauma.

What is the pathology of ectropion?

The exposed conjunctiva is vulnerable to irritants and bacterial infections, leading to recurrent conjunctivitis and scarring.

What is the treatment for ectropion?

V and Y blepharoplasty.

What is blepharitis?

Inflammation of the eyelids caused by infections or non-infectious conditions.

What are common causes of blepharitis?

• Infectious causes include bacteria (Moraxella equi) and parasites (oncocerciasis, habronemiasis);

• Non-infectious causes include dermatological conditions, photosensitization, and neoplasia.

What are the clinical signs of blepharitis?

Blepharospasm (blinking), hyperaemia, swelling, exudation, alopecia, pruritus, epiphora (tears).

How is blepharitis diagnosed?

History, clinical signs.

How is blepharitis treated?

Depends on aetiology and condition.

What are the most common eyelid neoplasias in horses?

Squamous cell carcinoma, sarcoid, melanoma.

What are the aetiology of neoplasia of the eyelids?

Depends on age, breed, lack of ocular pigmentation, genetics, UV radiation, infectious agents and chronic irritants.

How is eyelid neoplasia diagnosed?

Histopathological examination, biopsy.

How are eyelid neoplasia treated?

• BCG (Bacillus Calmette Guerin) – used to dissolve sarcoid (injection).

• Gamma-radiation (best). Resection could destroy eyelid margin.

What is distichiasis?

A double set of eyelashes: extra hair or cilia grow from the meibomian glands.

What is the treatment for distichiasis?

Surgical electrolysis.

What is trichiasis?

The inward direction of eyelashes, causing irritation through contact with the cornea.

What are common causes of prominence of the third eyelid?

Altered globe position or size, inflammation, neoplasia, tetanus, Horner's syndrome, prolapse of the orbital fat pad, or conjunctival amyloidosis.

What is the diagnosis of prominent nictating membranes?

Clinical signs, biopsy, cytology.

What is the treatment of prominent nictating membranes?

Depends on the underlying cause. Surgical or antitoxin.

What is conjunctivitis?

Inflammation of the conjunctiva, common in foals due to reduced tear production and low corneal sensitivity.

What is a primary cause of conjunctivitis?

• Irritants (environment, allergic, chemical).

• Foreign bodies.

• Infectious (Moraxella equi).

• Parasitic: Thelazia, Habronema musca, Onchocerca cervicalis.

What is a secondary cause of conjunctivitis?

Keratitis, disorders of tear production, trauma, systemic diseases, respiratory viral infections, or neoplasia.

What are the clinical signs of conjunctivitis?

Swelling, oedema, epiphora, discharge, and hyperaemia.

How is conjunctivitis diagnosed?

Physical exam, scraping and culture, Schirmer tear test, occasionally biopsy.

What is the treatment for conjunctivitis?

Depends on the cause but can include flushing, ophthalmic ATBs, and removal of parasites.

Which infectious disease causes a flag tail and prolapse of the third eyelid in horses?

Tetanus.

What organ, other than lacrimal glands, is related to overproduction of tears?

Nasolacrimal duct.

How is an obstruction of the nasolacrimal duct diagnosed?

Flushing, fluorescein stain, x-ray.

Where is the nasolacrimal duct opening located in the nose and the eye?

Nasal puncta on the ventral floor of the nasal vestibule; medial canthus of the eye.

What is the diagnostic method for dry eyes?

Schirmer’s tear test.

How can dry eyes be treated?

Artificial tears, synthetic mucins, topical cyclosporin A, eye catheter.

Where is an eye catheter inserted?

Through the eyelid (usually medial ⅓ of lower [avoids meibomian glands], but can use middle of upper with the tip resting in the conjunctival sac, secured with sutures.

What drug is contraindicated for eye ulcers?

Corticosteroids.

How are eye ulcers diagnosed?

Fluorescein stain.