In cats, this is often due to an issue with the immune system or the body's response to a virus. The top layer of the cornea is often left intact, defining the condition as “nonulcerative”. The term used to describe any inflammation of the cornea is “keratitis". In some cases, corneal tissue may even start to die, which creates edemas (abnormal fluid accumulations) and lesions in the eye. This condition can occur in cats of any age. Neutered male cats are recorded as having more diagnoses of nonulcerative keratitis than other sexes.

The cornea is the dome-shaped, clear exterior on the front of the eye. Its job is to refract light to the retina. When the cornea is irritated or injured, blood vessels will become present to start the healing process. These blood vessels opacify the cornea, making the eye look cloudy. If the irritation does not subside after a long period of time, the cornea floods the affected area with pigment (often brown, black or amber in color.) This creates permanent vision impairment to the cat.

The signs of nonulcerative keratitis will vary depending on the length of time that the cornea has been consistently irritated. This issue can present unilaterally (in one eye) or bilaterally (in both eyes). Symptoms to watch for are listed as follows:

This condition may be a small issue that does not severely affect the cat, or it can be related to life-threatening viral diseases. While genetics are not thought to be a main factor in nonulcerative keratitis development, Persian, Burmese, Himalayan and Siamese cat breeds are more commonly diagnosed with the issue. Known causes include:

Once at your veterinary appointment, you will need to provide the cat's full medical history to help identify possible underlying causes of nonulcerative keratitis. The veterinarian will then perform a complete physical examination of the cat. An ophthalmologic examination will also be done, magnifying the eye to get a clearer view of any misting or patches of pigment present. Foreign bodies may also be checked for at this time. Many tests may be done to differentiate this condition with other health issues that can cause corneal deposits or opacification.

As feline herpesvirus is often linked with nonulcerative keratitis, tests will be done to determine whether the cat has the virus or not. An immunofluorescent antibody assay (IFA) test may be performed, in which a blood sample is smeared on a slide containing cells. Cells in the cat's blood that are infected with the virus will be immobilized while normal cells will not be affected. A polymerase chain reaction (PCR) test can be used to expand the visuals of DNA to see if herpesvirus has affected the cat, or if another bacteria is present. To confirm that no ulcers are present, fluorescein stain may be applied to the eyes.  A scraping of the eye may be taken for cytological examination. A Schirmer Tear Test can be run to assess how much fluid is spreading around the eye. White blood cells, which become present in the case of an allergic response called “eosinophils”, should also be looked for. 

The appropriate course of treatment will depend on the underlying cause of nonulcerative keratitis that has been diagnosed. Many of these health conditions can be controlled but can not be cured. 

If an improper immune response is causing the issue, administering topical steroids to the eye for a lengthened period of time can clear up the problem. This treatment can last for up to 12 months.

Often paired with topical steroid prescriptions, antiviral agents such as nucleoside analogues, trifluridine or idoxuridine may be given if the cat has been determined FHV positive. Many of these medications are affordable and cats tolerate them well. Dosages can often be slightly lessened each week.

If severe pigmentation has occurred, a surgical procedure called a “keratotomy” may be performed. This includes shaving away the top layers of the cornea until no pigment remains. A graft may be needed to replace corneal tissue. If a foreign body or ingrown eyelash is causing the keratitis, these too can be surgically removed. General anesthesia is required for surgical procedures.

If bacteria in the eye has been identified as the cause of irritation, a corresponding antibiotic may be prescribed. These prescriptions generally last from 1-4 weeks. 

If your cat has undergone surgery, be sure to follow all instructions given by the surgeon at the time of your cat's discharge. Monitor the eye daily for signs of infection and ensure that it is kept clean. Your cat may need to be kept out of the sunlight during the healing process. A keratotomy surgery generally carries an excellent prognosis and is often the most successful form of treating nonulcerative keratitis in cats. 

Administer all medications as prescribed by your veterinarian. Lifelong treatment may be needed in cases of tear production issues. Periodic eye exams are needed in cases of medication therapy to ensure that dosages are correct and that no adverse side effects are developing. At first, they may be needed as often as every week or two, but appointments should lessen as treatment progresses. Opacification and pigmentation can recur after a full course of treatment has been given. Cats suffering from nonulcerative keratitis may continue to suffer from eye irritation, impaired vision and in extreme cases, blindness.