Special Report - Uveitis

Uveitis, a serious inflammation of the eye, is one of the most painful conditions to affect horses but its cause is still a bit of a mystery. If your horse becomes infected, there’s no reason why he can’t carry on as normal even if the eye has to be removed. Most can function with one eye at even the highest levels, including eventing and steeple-chasing.
Once a horse has had the condition, uveitis does have a habit of recurring, so it’s important to keep your own eye on the situation. Vets often refer to it as equine recurrent uveitis (ERU). It was first recorded in the fourth century, when it was thought to be connected with the moon’s cycle, so it is sometimes referred to as ‘moon blindness’. Another common name is periodic ophthalmia.
Any inflammatory condition of the eye is painful, but ERU is particularly painful and damaging. Each attack inflicts more damage, and the horse’s vision gets worse each time. In extreme cases, the eye is so badly damaged and the pain so difficult to control that surgical removal of the eye is the only humane option.

The symptoms
In the early stages of the disease, the symptoms will be similar to other, less serious, conditions and may easily be overlooked. It’s important to seek veterinary advice for all eye problems, because missing the opportunity to treat at this early stage can easily result in blindness or the loss of the eye.
Typically, the horse will have a watery eye and produce excess tears, the eyelids will be partially or fully closed and the cornea (the front of the eye) may look cloudy.
 

Side-effects
Atropine has side-effects which you must be aware of – it can cause colic and problems with the intestine. Although side-effects can occur, they’re not that common unless the vet is using high concentrations of atropine because the iris spasm is proving difficult to control.
One side-effect of atropine is that it can relax the iris, making the pupil very large. This in turn prevents the eye controlling the amount of light it lets in. This increase in pupil size may last from days to weeks and care must be taken to prevent the horse being exposed to strong sunlight until it has returned to normal. Uncontrolled exposure to strong sunlight can cause damage to the retina.
Applying these drugs to your horse’s already painful eye can be very difficult, particularly if the horse keeps the eyelids closed. You may spill the drops if he moves, so you need a great deal of patience to get it right and you may have to sedate him. 
As treatment may be required every two or three hours, it is often easier to place a catheter through the skin of the upper eye lid which allows drops to be put into the eye more easily. The drops will then be delivered to the underside of the upper eyelid and distributed over the surface of the eye. You should speak to your vet about this option.
Another way of treating the eye is for your vet to pass a fine catheter into the nostril and advance it as far as possible. This route delivers treatment into the space behind the lower eye lid and again avoids the struggle needed to persuade a horse to open closed eyelids which are attempting to protect a painful eye.
If you have a broodmare, light is really important because it stimulates normal springtime reproductive cycles. If she becomes totally blind through ERU she will have problems.
Although uveitis is quite common in the UK, in many cases the first attack or the early signs are missed because the symptoms can change or the horse may be resting in the paddock and not out working.
If the disease recurs, irreversible damage may already have been done but the long-term outlook for the horse can still be optimistic. Many horses go on to lead perfectly normal lives, even after surgery to remove the infected eye.
To give your horse the best chance of a normal life, it’s vital the condition is caught early, so always call your vet if you have any concerns about your horse’s eyes.