EYE DISORDERS
The prominence of a horse’s eye makes it vulnerable to injury and various other issues. Vet Lucinda Ticehurst explains what can go wrong and how it can potentially be put right
THE EQUINE EYE is particularly prone to injury due to its location, prominence and size. In contrast to human eyes, horses’ eyes have mainly peripheral vision, with limited forward sight and a large blind spot mid forehead. There are three common disorders that are often linked...
1SUPERFICIAL CORNEAL ULCERATION — A scratch on the outer layer of the eyeball is the most common type of eye injury.
Why/how does it happen?
■ Trauma — while grazing hedges.
■ Poor eyelid conformation and eyelash orientation.
■ Reduced tear function/blinking (check the other eye).
■ Foreign bodies. A corneal ulceration can progress to a bacterial or fungal infection and is very painful regardless of size, with a superficial ulcer actually being more painful than a more serious, deeper one.
Symptoms
These include (although the symptoms aren’t specific and can be indicative of any disorder causing eye pain)…
■ Pain — the eye may be partially closed.
■ Tearing — manifests itself as a watery discharge.
■ Pupil constriction — so that the iris is large and there is a very small pupil and minimal light can get to the back of the eye (as if the horse is standing in a really bright light).
■ Clouding of the cornea —a grey/white opacity can spread across the cornea.
Diagnosis
Fluorescein dye is applied onto the eyeball to gain a diagnosis. This orange dye turns to green when put into the eye and it sticks to the scratched area. A healthy cornea repels water, but if the top layer is damaged the water-based dye sticks to the layer underneath. However, the dye doesn’t stick to the lowest level of the corneal tissue with a really deep ulcer, but this should be a visually apparent defect without the use of a stain.
The green dye may come out of the nostril on the same side of the face, which ref lects a patent tear duct, and this can be a useful test when there are concerns that the tear duct is blocked. Once confirmed, a bacterial swab (culture and sensitivity so that the vet is able to choose a suitable antibiotic) and a fungal scrape may be undertaken to discover the most appropriate medication to use.
