What actually happens to a cat's eye with this condition?

The cornea is the transparent dome covering the front of the eye, and it stays clear because it has no blood vessels and a very specific cell architecture. Keratitis simply means inflammation of that layer, and when it happens without an ulcer eating into the tissue, veterinary ophthalmologists classify it separately because the underlying immune and infectious mechanisms differ from a mechanical injury (Merck Veterinary Manual, 2023). The two forms most often diagnosed in cats are eosinophilic keratitis, where a specific type of white blood cell infiltrates the cornea and conjunctiva, and corneal sequestrum, where a dark, dead patch of corneal tissue forms and can persist for weeks.

Both conditions can occur in one eye or both, and both are linked strongly to feline herpesvirus-1 (FHV-1), a virus that an estimated 80 to 97 percent of cats are exposed to at some point in their lives and that can remain latent in nerve tissue indefinitely (Cornell Feline Health Center, 2021). Stress, other illness, or immune suppression can reactivate the dormant virus and trigger a flare that shows up as ocular surface inflammation rather than the sneezing and nasal discharge typically associated with feline upper respiratory infections.

What do owners usually notice first at home?

The earliest visible change is often a subtle color shift on the eye itself: a white, gray, tan, or pink haze spreading across part of the cornea, sometimes with a raised, plaque-like texture in eosinophilic cases or a distinct brown-to-black patch in sequestrum cases (Merck Veterinary Manual, 2023). Some cats also develop a reddish, fleshy-looking growth at the edge of the cornea as blood vessels move in to try to heal the irritated tissue.

Discomfort varies considerably and that inconsistency trips up a lot of owners. A cat with an actively inflamed sequestrum may squint, paw at the eye, or avoid bright light, while a cat with a slow-growing eosinophilic plaque might show almost no pain at all despite visible corneal changes, according to feline ophthalmology reviews describing the condition's variable presentation (Cornell Feline Health Center, 2021). Excess tearing, a slightly closed eyelid, or one eye that just looks duller than the other are frequently the only early clues.

Why does this happen — is it always the herpes virus?

FHV-1 is the most consistently implicated trigger, but it is not the sole cause in every case, and some cats test negative for active viral shedding even when herpesvirus is suspected to be involved at the DNA level within corneal cells (Merck Veterinary Manual, 2023). Breed anatomy also plays a role in corneal sequestrum specifically: brachycephalic breeds such as Persians and Himalayans, along with Burmese and Siamese cats, are overrepresented in case series, likely because their prominent eyes and reduced blink efficiency leave the cornea more exposed to drying and irritation.

Chronic low-grade irritation from eyelid abnormalities, entropion (an inward-rolling eyelid), inadequate tear film, or old corneal scarring can also set the stage for these noninfectious-appearing inflammatory changes. Any condition that keeps the tear film unstable or the cornea repeatedly irritated raises the odds that inflammatory cells accumulate on the surface over time.

How does a veterinarian figure out what's causing it?

Diagnosis starts with a complete ophthalmic exam, and fluorescein stain is applied first to rule out an active ulcer, since the treatment approach diverges sharply depending on whether the surface is intact (Merck Veterinary Manual, 2023). A veterinarian will also check tear production with a Schirmer tear test and examine eyelid conformation, since anatomical contributors need to be addressed alongside any inflammatory disease.

For cases that don't resolve with initial treatment or that look atypical, a veterinary ophthalmologist may take corneal cytology or biopsy samples to identify eosinophils under the microscope, which confirms eosinophilic keratitis, or PCR testing of ocular swabs to detect FHV-1 DNA, though a positive PCR result doesn't always prove the virus is actively driving the current flare because latent virus can be shed intermittently in healthy-appearing cats (Cornell Feline Health Center, 2021).

What treatments actually clear this up?

Eosinophilic keratitis typically responds to topical corticosteroids or topical cyclosporine, applied several times daily for weeks, and many cats need months of tapering therapy to prevent recurrence once the visible plaque resolves (Merck Veterinary Manual, 2023). Because steroids can worsen an active herpesvirus infection, veterinarians often add an antiviral such as topical cidofovir or oral famciclovir when FHV-1 involvement is suspected, monitoring the cornea closely as doses are adjusted.

Corneal sequestrum is managed differently: mild, superficial lesions may be watched with lubricating drops and antiviral treatment to see if the dead tissue sloughs on its own, but many cases require surgical removal of the sequestrum (a keratectomy), sometimes paired with a conjunctival graft to support corneal healing, particularly when the lesion is deep or has been present for an extended period (Cornell Feline Health Center, 2021).

What does ongoing care look like once treatment starts?

Consistency matters enormously with these conditions because gaps in dosing can let inflammation rebound. Owners are usually asked to administer eye drops or ointment multiple times a day for several weeks, track whether squinting or discharge is improving, and return for rechecks so the veterinarian can confirm the cornea is healing rather than just less visibly inflamed. An e-collar is frequently recommended during active treatment since cats will rub an irritated eye and can worsen or reopen the area.

Reducing stress is also part of long-term management for herpesvirus-associated flares, since stress is one of the most consistent triggers for viral reactivation in latently infected cats; the AAFP recommends environmental enrichment, stable routines, and, in cats with frequent flares, discussion with a veterinarian about L-lysine supplementation or antiviral maintenance therapy, though evidence for lysine's benefit has become more mixed in recent studies (Merck Veterinary Manual, 2023).

Will my cat's vision and eye ever be completely normal again?

Prognosis depends heavily on how early the condition is caught and treated. Superficial eosinophilic keratitis often resolves with minimal residual scarring when treated promptly, while lesions left untreated for months can leave permanent corneal pigmentation or scarring that affects vision in that spot (Merck Veterinary Manual, 2023). Cats with corneal sequestrum that undergo surgical removal generally have a good outcome, though recurrence in the same eye or development of a new sequestrum in the other eye is possible, particularly in predisposed breeds.

Because FHV-1 establishes lifelong latency, cats with a herpesvirus-associated history of nonulcerative keratitis are prone to recurrence throughout their lives, especially during periods of stress, boarding, or concurrent illness, so many owners end up managing this as a chronic, flare-and-remission condition rather than a one-time problem (Cornell Feline Health Center, 2021).