Aetiology of corneal ulcers assume FHV-1 unless proven otherwise

Abstract

Overview: Feline ulcerative keratitis is a common presenting complaint and is frequently a sequela of feline herpesvirus 1 (FHV-1) infection; so much so, in fact, that it is fair to assume an FHV-1 aetiology until proven otherwise. Other potential causes of ulceration are trauma or underlying eyelid abnormalities (entropion, ectropion, agenesis, dermoids, neoplasia), lash abnormalities (ectopic cilia, trichiasis), tear film abnormalities or neurological deficiencies (trigeminal nerve paralysis, facial nerve paralysis).

Clinical challenges: The management of corneal ulceration in cats is frequently challenging, and treatment needs to be tailored carefully to the individual cat, its temperament, and the disease process present.

Evidence base: The scientific literature on feline ulcerative keratitis is extensive, particularly that related to FHV-1 infection. The aim of this article is to review the aetiology and diagnosis of corneal ulceration in cats with particular reference to the evidence base available.

Patient group: All age groups and breeds can suffer with ulcerative keratitis. Breed predispositions are present for some forms of corneal ulceration, and these are discussed.

Histopathology of the feline cornea

Fig 1.

Stromal ulcer

Morphological Types of Ulcer

Fig 2.

Diffuse oedema of the ventral cornea associated with keratic precipitate deposition, leading to endothelial dysfunction

Fig 3.

Symblepharon formation; in this case, there is an adhesion from the dorsal conjunctiva and third eyelid to the cornea

Fig 4.

Dendritic corneal ulcer — a pathognomonic feature of FHV-1 infection

Fig 5.

FHV-1 geographical ulcer. Note the faint corneal pigmentation, which represents early sequestrum formation

Fig 6.

Geographical superficial corneal ulcer with anterior uveitis

Fig 7.

Stromal keratitis. Note the vascularisation and hazy infiltrate at the leading edge of the vascularisation

Fig 8.

Histopathology of corneal sequestrum. Courtesy of Dick Dubielzig, COPLOW

Fig 9.

Central corneal sequestrum (plaque of corneal necrosis) in a Burmese cat. Note also the darkly pigmented dried discharge on the eyelids. The pigmentation is likely to be melanin

Fig 10.

Stromal keratitis and sequestrum formation in a Persian. This cat had been treated with a grid keratotomy; the grid lines are visible within the sequestrum

Ocular Sequelae Attributed to FHV-1

Fig 11.

Eosinophilic keratoconjunctivitis in a Maine Coon

Fig 12.

Scleral and corneal lacerations in a domestic shorthair cat

Fig 13.

Full thickness corneal perforation with prolapsed iris. Note the dyscoria due to iris entrapment in the corneal wound

Fig 14.

Corneal foreign body. Fluorescein has been applied to assess for aqueous leakage (Seidel's test)

Fig 15.

Lower lid entropion in an Abyssinian cat secondary to chronic ulcerative keratitis

Fig 16.

One-year-old domestic shorthair cat with unilateral eyelid agenesis. The left eye was microphthalmic with a micropalpebral fissure

Fig 17.

Three-month-old Birman kitten with epibulbar dermoid. Note the long hairs across the cornea

Fig 18.

(a) Domestic shorthair cat with left-sided trigeminal nerve paralysis secondary to an RTA. Note the severe central corneal exposure with stromal ulceration (tropicamide [Mydriacyl; Alcon Laboratories] had been applied to both eyes for retinal examination). (b) Close-up image of the left eye demonstrating severe stromal ulceration, deep corneal vascularisation, sequestrum formation and inflammatory cell infiltrate