Corneal Inflammation in Cats

The cornea is a clear layer over the eye that is important in directing light to the retina at the back of the eye. Corneal inflammation most commonly results in keratitis where the cornea becomes secondarily infected due to bacteria or viruses in the body. Ulcers or lesions in the eye may or may not be present. Keratitis can also be initially caused by traumatic injury which resulted in lacerations on the eye. Because it is infection-based, keratitis is very contagious from cat to cat and seems to affect mainly those cats who live at higher altitudes (due to a higher level of UV rays) as well as Persian, Himalayan, and Siamese cats. Initial infection may occur at birth and come from the mother.

Corneal inflammation occurs due either to effusion or edema stemming usually from a systemic infectious disease, but can also be due to trauma. The resulting condition can be keratitis (with or without ulcers), uveitis, or conjunctivitis. Each condition has similar symptoms, but treatments are slightly different. One very strong commonality, though, is that any issues having to do with ocular health must be treated quickly and aggressively before severe consequences occur such as blindness, removal of the eye, or death.

Symptoms of corneal inflammation often include:

• Red or swollen membranes in or around the eye
• Slow-healing sores on the eye
• Excessive tearing
• Squinting
• Yellow, milky white, green, blue, or red opacity (any that is not your cat’s normal eye color) 
• Raised white, pink, or gray corneal plaque with a rough surface
• Irregular or asymmetric pupils
• Pus-like or watery discharge
• Sneezing and nasal discharge (especially in younger cats)
• Pain and discomfort
• Dark brown or black discolored areas of the cornea

Types

Conjunctivitis

An inflammation of the pink membrane that covers part of the sclera (the white part of the eye) and the conjunctiva (inner eyelid). Can occur as a secondary response to an upper respiratory infection. 

Keratitis

Inflammation can be superficial or inside the cornea (interstitial), or be due to ulcers or lesions on top of the cornea. Inflammation can also be due to an immune system concern usually from a systemic infection. Keratitis can often be found in association with conjunctivitis (keratoconjunctivitis). 

• Eosinophilic Keratitis: Lesion(s) on the eye may be evident due to an intrusion of a type of granular white blood cell called eosinophils into the anterior chamber of the eye. 
• Ulcerative Keratitis: Slow-healing sores may be found in or on the cornea. It is usually caused by the feline herpesvirus-1. 

Both types of keratitis- ulcerative and eosinophilic- can affect any breed of cat. 

Uveitis

An inflammation of the uvea which includes the iris, ciliary body, choroid, and the retina. Blood cells that accumulate within the anterior portion of the eye creates a condition called hypopyon. Vision can be affected long-term by the development of cataract, glaucoma, or blindness.

All three types of corneal inflammation can be the result of, but not limited to, a feline herpesvirus-1 infection. It is rare for a cat to become completely blinded. However, your cat may experience long-term pain and discomfort if the condition is not properly treated. Causes of inflammation include:

• Feline immunodeficiency virus (FIV)
• Feline herpesvirus-1 (FeHV-1)
• Toxoplasmosis (a parasite that can be found in undercooked meat)
• Feline leukemia virus (FeLV)
• Feline infectious peritonitis (abdominal infection, FIP)
• General fungal or bacterial infection
• Feline chlamydia
• Feline mycoplasma
• Hypertension
• Traumatic injury
• Excessive levels of lipids or calcium deposits in the tissue underneath the cornea (the stroma)
• Corneal laceration
• Cancer

Taking your cat’s medical history and observing clinical signs during physical and ocular examinations may be enough for your veterinarian to make a diagnosis. If the cause is not readily apparent, however, laboratory testing may be ordered. Identifying which infectious organism is causing the inflammation will direct the manner of treatment since it is primary in protecting your cat’s vision.

Cytology

Your veterinarian may want to collect a few conjunctiva or corneal cells for closer inspection by microscope (cytology). The discovery of white blood cells indicates that a foreign organism is present and further testing is needed to differentiate between an immune related cause and an infectious disease. 

Schirmer’s Tear Test

If mucous and the appearance of conjunctivitis is present, a Schirmer’s Tear Test will be performed to assess if your cat normally has adequate tear production since it can be a contributing factor.

Polymerase Chain Reaction Test (PCR)

This test may be conducted since it is the most sensitive diagnostic test available today for ocular diseases. The test involves performing a biopsy on the affected area and sending it to a laboratory for DNA evaluation for the presence of a virus. Repeated samples submitted for testing may be necessary. 

Blood Tests

Additional tests for underlying systemic conditions will be conducted through blood tests since corneal inflammation is mainly associated with an unknown pathogen or disease. A complete blood count, serum chemistry profile, and tests for feline leukemia, feline immunodeficiency virus, and feline herpesvirus-1 will be performed.

Fluorescein Stain

A harmless and painless fluorescein stain will be applied directly to the eye. The stain sticks wherever deterioration, a foreign object, scar, inflammation, or an ulcer may be on the cornea. A blue light shone onto the eye will reveal the issue. This test will be conducted last so that the stain does not inadvertently hide any clinical findings.

If feline herpesvirus-1 is the cause of the condition, if your cat’s condition is not improving or is worsening, or if there is no apparent cause, your veterinarian will likely refer you to a board-certified feline ophthalmologist.

Medication

The use of anti-inflammatories is currently the best way to control the condition and bring relief to the cat in most cases. Corticosteroids administered topically, systemically, or subconjunctival will be prescribed and is often sufficient. Other anti-inflammatory medications may also be prescribed. Antiviral and antibiotic medications in combination with steroid therapy are usually given to address any underlying systemic conditions and to prevent any secondary infections. Medication may need to be administered 2-4 times a day over a 4 to 6-week period. 

If feline herpesvirus-1 is the cause, antiviral therapy will be more aggressive since it can lead to blindness, discomfort, and long-term pain if it is not quickly controlled. 

Surgery

In some cases, a keratectomy may need to be performed to remove dead, infected, or deteriorated areas of the eye due to an ulcer or lesion that is worsening despite treatment. The procedure may also be performed if the infection has been ongoing and scarring is prevalent. Removing the scars will enhance your cat’s vision and tear drainage ability. Additionally, if the eye is ulcerated enough, a conjunctival graft may be performed to help ensure the long-term health of the eye by introducing new blood vessels into the affected area. 

Your veterinarian will want to examine your cat every 1-2 weeks to ensure that the treatment is working. If your cat is responding well, these appointments will become less frequent over time. 

Bacterial and chlamydial infections usually respond well to treatment and the prognosis will be good. Viral infections, on the other hand, are usually slow to respond and can sometimes reoccur even after a full course of antiviral therapy. The kind of treatment your cat receives may be adjusted as necessary in order to prevent pain, vision loss, and blindness. However, it should be noted that in cats with severe cases, these outcomes may still be possible. The development of secondary glaucoma will also be closely monitored during follow-up appointments. 

At home, it is important that you administer the medications your veterinarian prescribes very precisely. Any deviation from the treatment your veterinarian recommends could cause serious consequences to your cat’s ocular health. 

Your veterinarian may also suggest certain supplements to help support your cat’s immune system and to relieve any cell damage if your cat has feline herpesvirus-1. It is recommended that you give these supplements as directed to your cat in order to enhance the success of the treatment. 

You should also reduce stress on your cat as best you can. Like cold sores in humans, stress often aggravates the virus in your cat and can cause additional outbreaks of sores or lesions, which leads to ongoing treatment. Examples of stress may include introducing a new pet to the household, moving households, boarding, large gatherings within the household, and the like.

Presently, there is no cure for conjunctivitis or keratitis. It can only be controlled with careful treatment and close monitoring. There will be periods of time when your cat’s eyes will appear normal, but occasional flare-ups can occur either frequently or perhaps years apart, while some cats never have a recurrence.