Ophthalmology Feline Conditions

Feline herpesvirus (FHV) associated diseases

Conjuntivitis due to FHV

Feline herpesvirus (FHV) is one of the most common ophthalmic diseases of the cat. The clinical signs vary and range from mild conjunctivitis to severe corneal ulceration with perforation and loss of the eye. Signs of upper respiratory tract infection (sneezing, runny nose) may or may not accompany the ophthalmic problem. The virus is transmitted easily from cat to cat, but does not affect humans. The virus does not stimulate good immunity following infection. Persistent latent infections often occur, with the virus becoming reactivated following periods of stress. Cats may carry the virus for life, with periodic shedding of the virus and reoccurrence of ocular disease.

Symptoms
The most common form of FHV is acute conjunctivitis with discharge, redness and some degree of discomfort. In the initial infection, signs of upper respiratory tract infection usually occur, with remission in 10-14 days. Sometimes signs persist in the form of chronic conjunctivitis or keratitis (inflammation of the cornea). Occasionally dryness of the eyes or corneal sequestrum may occur. Kittens are usually more severely affected.

Treatment
Treatment depends on the type of clinical signs present. Antibiotics may be used to prevent secondary bacterial infection, especially if an upper respiratory tract infection is present. Antibiotics however, have no effect on viruses. These medications can be expensive and time consuming, with the possibility of allergic reactions. Antiviral drugs are usually used when the cornea is affected and may also cause chronic conjunctivitis. Many cats are also treated with a dietary supplement of an amino acid called L-Lysine to help decrease reoccurrence.

Corneal Sequestrum

Note the brown-black
plaque near the center
of the eye

Corneal sequestrum is an unusual and unique disorder affecting the cornea of cats. A brown-black plaque forms in the corneal tissue, often causing significant discomfort. The cause of the problem is not known. Persian and Himalayan breeds are affected most frequently, but any breed can develop this problem. In over 50% of cases, a corneal ulcer or abrasion has preceded the formation of the sequestrum. There are sometimes other predisposing factors, especially feline herpes virus.

Symptoms
A brown-black plaque forms in the corneal tissue, often causing significant discomfort. The eye may be squinting, tearing, and appear red.

Treatment
There are two treatment options for corneal sequestrum. The first option is to medicate the eye with topical antibiotics and lubricants to prevent infection while waiting for the sequestrum to slough (fall off). The average time to heal is three months. This can be a painful process, and occasionally results in a very deep defect and possible corneal rupture. Because of this, surgical removal of the sequestrum is usually recommended. Surgery is performed under general anesthesia and the average healing time is three to four weeks. Surgery is performed under general anesthesia. The cat is usually required to wear an Elizabethan collar to protect the eye until it heals. With either treatment, there is a 12% reoccurrence rate of sequestrum formation.

Eosinophilic Keratitis

Note the pink plaque

Eosinophilic keratitis is a unique, chronic inflammatory disease of the feline cornea. Eosinophils, a type of white blood cell, can invade the cornea causing a vascular appearing mass to arise. Signs of discomfort (squinting, tearing, and rubbing at the face) are inconsistent. The typical appearance of eosinophilic keratitis is a white-pink plaque-like lesion that often has a gritty texture. These lesions can migrate across your pet’s cornea and may gradually impair vision. It is not currently known why this disease occurs, but it has been associated with feline herpes virus.

Symptoms
Signs of discomfort (squinting, tearing, and rubbing at the face) are inconsistent. The typical appearance of eosinophilic keratitis is a white-pink plaque-like lesion that often has a gritty texture. These lesions can migrate

Note the white plaque

across your pet’s cornea and may gradually impair vision.

Treatment
Treatment generally utilizes topical corticosteroids and other options are available in certain situations. Initially, medication is given at a frequency of 3-4 times daily. After several weeks this frequency may be reduced to 1-2 times daily or even 1-2 times weekly to maintain control. It is unusual to have treatment stopped completely.

Corneal Ulcers

An advanced corneal
ulcer

A corneal ulcer is a scratch or abrasion on the outside clear part of the eye and is usually caused by trauma. This clear portion of the eye, called the cornea, is composed of many layers. When the cornea is scratched, cells are lost leaving a defect, which is known as an ulcer. Ulcers usually heal rapidly without complications. However, an ulcer may become worse if neglected, treated improperly, or if normal healing is interfered with. In severe cases, an ulcer can lead to loss of the eye.

Symptoms
Common signs that a corneal ulcer is present include: squinting (due to pain), a “red eye”, excessive tearing, rubbing or pawing at the face, and often an ocular discharge.

A mild corneal ulcer
Treatment
Preventing infection and controlling pain are the two most important features of treatment. Topical antibiotics will be used to prevent infection and topical atropine may be used to help control pain. If a condition exists that interferes with normal healing, it may also require treatment. It is extremely important to follow all medication instructions.

Your pet may want to rub or scratch at its eyes or face, especially after applying the medications. If the problem occurs for a few minutes after the eye medication has been used, distract your pet by playing with or petting him/her. If the problem continues or if severe rubbing occurs, please contact us or your regular veterinarian to obtain an Elizabethan collar.