Common eye problems
By Chris Dixon
09 July 2012 09:46
Chris Dixon BVSc CertVOphthal MRCVS, a veterinary ophthalmologist, gives his advice on the most common eye problems that occur in horses.
Damage to the cornea is often referred to as an ulcer by veterinary surgeons. Minor superficial ulcers should heal within a few days, but if it becomes infected or the ulcer extends into the deeper layers of the cornea, treatment is required to alleviate the pain and prevent any loss of vision.
Uveitis, an inflammation of the internal structures of the eye, is an extremely painful condition that creates a spasm or cramp of the internal muscles pulling the horse’s pupil into a slit. There are many causes of uveitis and some horses, such as Appaloosas and Warmbloods, are prone to repetitive bouts of inflammation called Equine Recurrent Uveitis (ERU) - this used to be called moon-blindness because it was thought that each bout was caused by the movement of the moon.
Over the years many studies in different countries have tried to find the cause of ERU and we now know that the disease is related to a stimulation of the horse’s immune system. However ERU doesn’t have a single cause and many factors may contribute to its inception. Studies have demonstrated links to genetic makeup, bacterial and viral infection, trauma and UV light.
Professor Brian Gilger and his associates in the USA have developed a new treatment for ERU. It involves the placement of an implant into the tissues at the back of the eye. The implant is a small disc impregnated with a drug called cyclosporine that’s slowly released into the eye. It’s been demonstrated that a single implant can last longer than three years and will delay the progression of the disease. The implant doesn’t affect the horse’s vision and we haven’t seen any evidence of discomfort following placement of the implants at our centre.
Cataracts are opacities of the lens. They prevent the passage of light through the eye onto the retina and there are many types of cataract, some worse than others. Unfortunately once a cataract has formed there’s no medication currently available that can reverse the changes. If the cataract is impairing vision and the eye is otherwise healthy, surgical removal can be considered. A method called ‘phacoemulsification’ is used to remove the cataract and a plastic lens can then be inserted into the eye, to give the horse the best possible vision.
Eyelid swelling is common and can arise from a variety of causes. Examples such as simple trauma and fly-bites resolve quickly, but any lumps that persist should be checked for signs of cancer. Sarcoids can occur close to the eye and there are different treatments available depending on the type of sarcoid seen. Horses with non-pigmented skin are especially prone to sunburn and the use of protective creams or a fly-mask can help to reduce exposure.