Iris cysts are a common finding in the equine eye. More often than not, they do not cause any issues and are an incidental finding. Some; however, can grow to a size where they begin to affect a horse’s vision. Such horses generally present to us due to spooky behaviour. This is most apparent in sunny conditions, when the horse’s pupil is small and the cyst blocks light rays from reaching the back of the eye.

Treatment options

We will recommend treating iris cysts if we feel they are clinically significant – the horse in question is showing visual deficits or has started to spook.

Traditionally the treatment for iris cysts was laser ablation. We recently undertook a new technique to drain an iris cyst called ‘standing trans-corneal aspiration.’ This technique, which can be performed in suitable candidates, is performed under standing sedation, and local anaesthesia of the eye. A very thin needle is inserted into the eye, and the fluid from inside the cyst drained. The patient requires minimal medication following the procedure and most tolerate it really well.

If you would like to know more about iris cysts, please get in touch to discuss it with one of our equine vets.