Affects: Cats, Dogs
A corneal ulcer, or ulcerative keratitis, is an inflammatory condition of the cornea involving loss of its outer layer. It is very common in dogs and is sometimes seen in cats. In veterinary medicine, the term corneal ulcer is a generic name for any condition involving the loss of the outer layer of the cornea, and as such is used to describe conditions with both inflammatory and traumatic causes.
Symptoms: Ocular Pain
Blepharospasm
Increased lacrimation
Photophobia
Corneal Oedema (1⁰/2⁰)
Causes: A distinct cause for initial ulceration is not commonly found, although in many cases it can be assumed to be traumatic in origin. The horse's eye is especially vulnerable to trauma due to its prominent position, compared with other species. Exposure keratitis (inflamed cornea) can occur in the horse, most commonly secondary to facial nerve paralysis. Hospitalised animals have been shown to have a decreased corneal reflex, and this corresponds to an increased incidence of ulcers in the hospitalised population. Foreign bodies embedded in the palpebral conjunctiva or the nictitating membrane can cause persistent irritation and ulceration. Often the shape and distribution of the lesion is suggestive of this aetiology, but even in the absence of a characteristic lesion their presence should be considered and sought out.
Bacterial and fungal infection occurs readily after the initial ulceration, as disruption of the corneal epithelium allows attachment and colonisation of the underlying tissues by normal corneal commensals. Commonly isolated bacteria include Staphylococcus, Streptococcus and Pseudomonas, and empirical anti-microbial therapy should be effective against these bacteria.
Diagnosis: Differential diagnoses for the painful equine eye:
Ulceration
Uveitis
Treatment: Medical therapy should be based upon the severity of disease initially, and then by the response to therapy. The aims of the initial therapy are:
Antibiosis
Analgesia
Anti-inflammatory