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. Symptoms
Ocular Pain
Blepharospasm
Increased lacrimation
Photophobia
Corneal Oedema (1⁰/2⁰)
Scleral injection
Conjunctivitis

Diagnosis
Differential diagnoses for the painful equine eye:

Ulceration
Uveitis
Blepharitis
Conjunctivitis
Glaucoma
DachrocystitisA full ocular exam should be performed for every case of eye pain. Fluoroscein staining is usually diagnostic for corneal ulcers, although staining with Rose Bengal is also recommended as it can pick up early viral/fungal lesions, which will appear as multifocal disturbances to the tear film. Culture and sensitivity is recommended for rapidly progressive or deep corneal ulcers. Cotton swabbing is often inadequate, and corneal scraping, for example, with the blunt side of a scalpel blade is usually required. This can be greatly facilitated by the use of local nerve blocks and topical anaesthesia. There is almost invariably a secondary uveitis present with corneal ulceration, and signs of this may also be seen: miosis, corneal oedema, aqueous flare, hypopyon, IOP changes. 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
MydriaticThe initial choice of antibiotic depends upon personal choice, experience and availability, but could include chloramphenicol, chlortetracycline, bacitracin-neomycin-polymyxin (BNP), ciprofloxacin, ofloxacin and tobramycin. Topical gentamicin formulations are also available, but in the opinion of some, should be reserved for cases with stromal melting.
Corneal ulcers in cats
Corneal ulcers in cats can be caused by trauma, detergent burns, infections, and other eye diseases. One common cause not seen in dogs is infection with feline herpesvirus 1 (FHV-1). FHV-1 causes ulceration by direct infection of the epithelial cells. Lesions appear as round or dendritic (branching) ulcers. FHV-1 also suppresses healing of the cornea. Symptoms include conjunctivitis, squinting, eye discharge, and blood vessels on the cornea. It can cause severe scarring. Treatment is with topical antiviral drugs and antibiotics, and oral L-lysine, which competes with arginine and inhibits viral replication. Corneal ulcers in horses
Corneal ulceration is a very common disease of the equine eye and can have sight-threatening consequences. Aggressive treatment is always indicated, as even apparently mild ulcers can progress quickly, causing serious complications. 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 horses 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.