Iris cysts are fluid filled bodies, typically dark in colour and sperhoid in shape, appearing at the pupil margin of the eye. They are a relatively frequent ocular abnormality observed across the general horse population. Whilst the majority of cysts are small, having no adverse impact on the patient or the health of the eye, a small percentage of horses may exhibit a loss in performance and behavioural changes as a result of developing a cysts (sometime multiple cysts). This tends to occur where the cyst is large enough to affect the individual’s visual field and where an individual struggles to adapt to this altered view of the world.

Iris cysts in horses can be diagnosed by direct observation and tend to photograph well with smartphones. Where a more detailed examination is required, a specialized instrument called a slit lamp biomicroscope allows for very detailed evaluation of structures with the eye.

Thankfully, there is a safe and effective treatment option for iris cysts in horses. The use of a specialized ophthalmic laser can eliminate the cyst without the need for invasive surgery. The procedure is minimally invasive, and can be performed on-site, without the need for general anaesthesia. The reduction in cyst size and gains in vision are immediate with minimal aftercare and minimal time off work.