Keratitis, inflammation of the cornea, is among the most common and potentially serious eye diseases in horses. The eye's exposed position and its susceptibility to injury often lead to considerable pain and secondary infection. In severe cases, permanent visual impairment or loss of the eye may follow. Every case of keratitis requires prompt veterinary assessment.
Types and causes
- Ulcerative keratitis: Damage to the corneal epithelium predominates, usually after mechanical trauma (e.g. foreign bodies, straw, plant material). Bacterial or fungal infection may follow. Aspergillus and Fusarium are among the common fungal pathogens in horses.
- Non-ulcerative and immune-mediated keratitis: Chronic, non-infectious forms arise from immune reactions in the cornea without a primary epithelial defect. A possible role of viruses such as EHV-2/5 is discussed but not clearly established.
Clinical signs
- Blepharospasm and photophobia
- Epiphora
- Redness and swelling of the conjunctiva and eyelids
- Corneal opacity, erosion or ulceration
- In advanced cases, corneal vascularisation and scarring
Diagnosis
A systematic ophthalmic examination is essential:
- Fluorescein staining, and rose bengal staining where appropriate, to show epithelial defects
- Schirmer tear test to assess the tear film
- Slit-lamp examination of the cornea
- Cytology and culture of corneal samples
- PCR to detect organisms that are difficult to culture
Veterinary management
The choice of measures rests with the veterinarian and depends on the type and severity of disease. Assessment and management of corneal lesions are carried out exclusively by the veterinarian.
- Removal of foreign material and necrotic tissue
- Pain management and control of secondary uveitis
- Protection of the eye, for example with a fly mask or eye guard
- Medicines at the veterinarian's decision, e.g. antibiotics based on susceptibility testing, antifungals where fungi are involved, and atropine for cycloplegia. Corticosteroids may be contraindicated in infectious keratitis.
- Surgery for deep ulcers, descemetocele, perforation or abscess, ranging from conjunctival flaps and grafts to enucleation