Eye Injury in Cats: Ulcers, Stains, and the 24-Hour Window

A cat squinting at one eye, tearing, or pawing at its face needs to be seen today. A corneal ulcer can go from a surface scratch to a hole in the eye in under 24 hours, and the difference between an eye that heals and one that is removed is usually how fast it was treated. Do three things now: stop the cat from rubbing, keep every human eye drop away from it, and call a vet who can stain the cornea.

Signs that mean today, not tomorrow

Some eye problems can wait until morning. These cannot:

• Pupils of different sizes, or a pupil that stays wide in bright light.
• A cloudy, blue, or blood-tinged eye, or an eye that looks swollen and hard.
• Squinting with thick yellow or green discharge.
• Sudden blindness, bumping into furniture, or the third eyelid sliding across half the eye.
• Anything that started after a fight, a fall, a car trip, or contact with a cleaning product.

Pupil size is the single most useful thing to check. Equal pupils that shrink when you shine a phone light are reassuring. Unequal or fixed pupils, a bulging eye, or an eye that feels rock hard point to pressure building inside the globe, and that pressure crushes the optic nerve within 24 to 48 hours. Glaucoma is painful enough that many cats stop eating.

Why the clock runs fast

The cat cornea is only about 0.5 to 0.6 mm thick, and the surface layer that keeps bacteria out is a few cell layers deep. Once a scratch strips that layer, tear film and bacteria reach the stroma underneath. Bacteria and the enzymes they release digest the stroma, so the defect gets deeper even while the cat is resting. A ulcer that is 30 percent deep at 9 a.m. can reach the last thin membrane by the next morning, and that membrane ruptures under normal blinking pressure.

Two things speed this up: a dry eye, which leaves no tear film to dilute the enzymes, and a cat that keeps rubbing the eye with a hind paw. Both are common in the first 12 hours.

What the vet does with the stain

Fluorescein dye is the core test. A drop goes on the eye, the surface is rinsed, and a cobalt blue light is used. Healthy cornea sheds the dye; damaged cornea holds a bright green patch, and the shape of that patch tells the vet how deep and how large the defect is. A dark spot in the middle of a green area suggests the ulcer has eaten down to the last membrane, which is a surgical case, not a drop case.

The same visit usually includes a Schirmer tear test (a normal cat reads roughly 15 to 25 mm of wet strip in a minute), a pressure reading (about 15 to 25 mmHg is normal), and a look under the lids for a foreign body such as a grass seed. Unhealed ulcers are re-stained every 24 to 48 hours, because a ulcer that is not shrinking after 5 to 7 days needs a different plan.

Why human eye drops are dangerous

This is the mistake that costs cats their eyes. Steroid drops such as dexamethasone or prednisolone shut down the repair response and let bacteria melt the stroma, so a ulcer that would have healed in 5 days can perforate in 24 hours. Miotic drops such as pilocarpine constrict the pupil and worsen the pain and inflammation of a damaged eye. Decongestant drops mask redness without treating anything, and preserved artificial tears sting an open wound.

Never use drops left over from another pet, drops past their expiry date, or any bottle that does not name the active ingredient. If a vet has already prescribed treatment, keep to that bottle and that schedule only.

The cone has to actually stay on

A cat rubs its eye with a hind foot, not a front one, so a collar that sits low on the neck does nothing. Soft fabric collars are comfortable but most cats learn to hook a claw under the edge and flip them off within a day; a determined cat can also fold them back far enough to reach the face. Use a rigid collar sized so the rim sits past the tip of the nose, and check that two fingers fit under the neck strap.

Plan on 7 to 10 days, and keep it on at night and while you are out. Take it off only for watched meals. A cat that stops eating in a collar usually eats better from a shallow saucer raised 5 cm off the floor.

Chemical burns: flush before you drive

Alkaline products such as oven cleaner, drain gel, and some floor cleaners keep burning for hours after contact. Do not wait for the appointment. Hold the cat's head under a gentle stream of saline or lukewarm tap water for a full 15 minutes, running from the inner corner outward so the rinse does not push chemical into the other eye. Do not try to neutralize an acid with a base or the reverse; the heat from that reaction causes a second burn.

Flush both eyes if you are not sure which one was hit, then go in. A vet will keep flushing under sedation, check the pH of the tear film, and stain for dead tissue.

If the eye is out of the socket

Prolapse is rare but happens after a blow to the head. Cover the eye with gauze soaked in saline, keep it wet on the drive, and do not press on it or try to push it back yourself. Pressure on a swollen optic nerve does more damage than the original injury. Surgery within a few hours gives the best chance of saving the eye, and removal is the outcome when the nerve and blood supply are already gone.

What to do in the next hour

1. Put a rigid cone on before anything else.
2. Do not touch, wipe, or flush the eye unless a chemical is involved.
3. Photograph the eye with your phone so the vet can see how it looked at the start.
4. Call ahead and say "possible corneal ulcer" so the clinic sets up the stain.
5. Carry the cat in a carrier with a towel over it, and skip food if surgery may be needed.

Wounds that involve the eyelid or the tissue around the eye follow the same rules as other injuries; see bleeding and wounds. Keeping cleaners and sharp objects out of reach prevents most of these cases, and the room-by-room list in cat-proofing your home is a good place to start.

Frequently asked