My pet has a corneal ulcer

Your dog or cat seems to have a problem with one of its eyes. It is impossible to look at it closely because it blinks so much. What if it is a corneal ulcer ?

The cornea

The cornea is the front, transparent part of the eye. In dogs and cats it is between 0.5 and 0.8 millimetres thick. This tissue is not vascularised, so it does not receive the oxygen and nutrients necessary for its proper functioning via the blood, like the vast majority of other organs, but mainly via the tear film and the aqueous humour.

A corneal ulcer is a loss of substance in the cornea. The superficial layers of the cornea are more innervated than the deeper layers, so the more superficial the ulcer, the more painful it is, i.e. when it affects less than 1/3 of the thickness of the cornea. Medium or deep ulcers therefore tend to be less painful, but the risk of perforation and loss of the eye is greater.

In the presence of a corneal ulcer, the animal shows signs of eye pain: it may rub the area with its paw, it closes its eyelids very regularly or permanently, and the eye is red and watery. If the pain is important , your dog or cat may be less active than usual, or eat less.

How does a corneal ulcer occur ?

Corneal damage can occur for a number of reasons. Probably the most obvious is trauma: a scratch from a fellow dog or a branch from a shrub that rubs and damages this fragile surface. An ulcer can also occur as a result of repeated aggression, such as a lack of tears, or when the eyelids cannot perform their function. Indeed, it can happen that they do not close properly.

• because of a neurological problem,
• because they are too “short” in relation to the eyeball – this is called lagophthalmos – or because the eyeball is too large – this is called buphthalmos, which differs from exophthalmos (in this case, the eyeball is of normal size but protrudes abnormally from the orbit),
• because a mass or eyelashes are present on their free edge or inner surface and rub against the cornea with each blink, …

Finally, in cats, the appearance of an ulcer may be the result of an infection by the feline herpes virus. This virus is frequently responsible for recurrent conjunctivitis as well as corneal ulcers described as dendritic (because they have a particular, very characteristic, branched tree-like shape). The virus can also cause keratoconjunctivitis sicca in affected cats, which damage the cornea.

My dog or cat seems to have an eye injury, is it urgent to consult ?

If you suspect that your four-legged friend has a corneal lesion, it is prudent not to delay consulting your veterinarian. Indeed, an untreated ulcer can be complicated by a bacterial or fungal superinfection. Also, if the lesion progresses, the eye may perforate.

To find out if the corneal surface is damaged, your vet will perform a fluorescein test. He or she will apply a drop of green dye (which appears orange before instillation) directly to the eye, rinse the eye with saline or a suitable eye wash and check, using a blue light, whether the dye has attached to the corneal stroma – the second layer of the cornea. If this is the case, a corneal ulcer is present.

How can a corneal ulcer be healed ?

If a corneal lesion is present, your vet will prescribe :

• A gel or eye drop containing an antibiotic to manage or prevent bacterial superinfection,
• An ocular lubricant to lubricate and moisten the corneal surface – depending on the molecules used in the formulation, a lubricant may help regenerate the corneal surface in the case of injury,
• a painkiller in the form of a syrup or tablets – in some excessively painful cases, the local use of atropine drops is essential.

Your vet will also recommend the use of a collar to avoid any scratching or rubbing, which could obviously delay the healing of the wound.