An eye ulcer is a scratch or sore through the clear front layer of the eye, the cornea. In dogs it is usually an injury: a claw, a stick, a rub along the carpet, rough play with another animal. In cats it is usually the herpes virus. Most heal within days on the right drops. The ones that go wrong do it fast, and one of the ways owners make an ulcer worse is with the wrong eye medicine from the cupboard. Everything here comes from the veterinary ophthalmologists' college, the Merck Veterinary Manual, Cornell's feline health center and two studies of which dogs get ulcers, and each is linked at the bottom.
The signs are the same in dogs and cats: squinting, an eye held half or fully closed, tears or a sticky discharge, rubbing the eye with a paw or along the carpet, redness, a cloudy look to the front of the eye, and turning away from bright light.
An ulcer usually cannot be seen without a test, so a squint is worth a call to the vet the same day. The ophthalmologists' college gives the reason in one line.
The test is simple. The vet puts a drop of an orange dye called fluorescein on the eye. The dye sticks wherever the surface is broken and glows green under a blue light, so an ulcer shows up as a green patch.
A simple ulcer is treated with antibiotic drops or ointment, often every four to six hours, something for the pain, and a cone so the eye cannot be rubbed. Merck mentions atropine drops, which widen the pupil and ease the ache. The vet repeats the dye test to confirm the ulcer has closed, and the drops continue until then, even once the eye looks better. VCA's advice is never to stop them without the vet's approval.
In plain words: steroids stop the surface from growing back and help the enzymes that dissolve the cornea, which is how a small ulcer becomes a melting one.
The VetCompass study at the Royal Veterinary College went through a year of records for 104,233 dogs at 110 practices in England. About 1 dog in 125 had an eye ulcer that year. The breeds at the top of the list are the ones with short noses and prominent eyes.
| Breed | Had an eye ulcer that year | Against a crossbred dog |
|---|---|---|
| Pug | about 1 in 18 | over 19 times the risk |
| Boxer | about 1 in 20 | 12 times the risk |
| Shih Tzu | about 1 in 29 | 10 times the risk |
| Cavalier King Charles Spaniel | about 1 in 40 | not given for this breed |
| Bulldog | about 1 in 41 | not given for this breed |
| All dogs in the study | about 1 in 125 |
Flat-faced breeds as a group had over 11 times the risk of crossbred dogs, and dogs aged six to nine had about twice the odds of dogs under three.
A second study, of 700 dogs at a referral hospital in England, measured the faces. Flat-faced dogs were twenty times more likely to have an ulcer. A fold of skin over the nose made one nearly five times more likely, eye white that shows when the dog looks straight ahead nearly three times, and a wider eyelid opening raised the risk sharply. The authors' conclusion is that breeding for these faces greatly raises the risk, and that it should be discouraged.
For an owner of one of these breeds, that comes down to three things: know the signs, keep the vet's number where you can find it at night, and treat any squint as urgent.
Some ulcers in dogs are shallow and simply fail to heal, or heal and come back. Vets call them indolent ulcers, or SCCEDs. Drops alone do not fix them. They turn up mostly in middle-aged and older dogs, and VCA names Golden Retrievers alongside the breed that gets them most.
Treatment is done at the clinic: the vet removes the loose, damaged surface and then either scratches a fine grid into the cornea or polishes it with a diamond burr, to stimulate new growth. If an ulcer has not healed in a week, it is worth asking whether it is this kind.
In cats the usual cause is a virus, not a scratch.
The virus stays in the body and flares up again, which is why the same cat can get ulcers more than once. Treatment can add an antiviral to the antibiotics. Two cautions apply to cats in particular.
A sequestrum is a patch of cornea that dies and turns dark. Only cats get it, most often Persians, Himalayans and Siamese, and it is treated with surgery. So the grid treatment used on Boxers is not one for a cat, and a cat's ulcer that is slow to heal is a question for a veterinary ophthalmologist.
Go the same day, or to an emergency clinic at night, if the eye gets worse on treatment, the cornea around the ulcer turns cloudy white, the ulcer looks deep, or anything bulges from the surface of the eye. Merck describes deep ulcers where the inner layer of the cornea pushes through, or the ulcer becomes a hole, and many deep ulcers need a graft of the pink tissue from around the eye to strengthen the cornea.