Transcorneal aspiration for management of primary iris cysts in the standing horse

Equine primary iris cysts are usually incidental findings but, if associated with clinical signs, may require intervention. The use of laser (Nd:Yag or diode) has been reported but requires specialised equipment. Transcorneal aspiration has not been previously evaluated in the standing horse.

To review outcomes of standing transcorneal aspiration of primary iris cysts (STAPIC) in horses.

Horses were identified from electronic patient records from 2018 to 2024 across four collaborating centres. Clinical presentation and outcomes were identified and reported using descriptive statistics.

Eighteen horses were identified. Behavioural signs reported included 'spooking' and changes in rideability often associated with jumping. Single large unilateral cysts were present in 11 horses, bilateral cysts in three horses and multiple unilateral cysts in four horses. Following treatment, one horse developed uveitis and fibrin in the anterior chamber associated with needle contact with the iris stroma due to movement, and a second horse developed fibrin within the anterior chamber. Both conditions resolved with anti-inflammatory medication and administration of tissue plasminogen activator. No other adverse effects were reported. Follow-up was available from all horses (median: 6 months, interquartile range [IQR]: 4-11 months) with no recurrence, although one horse developed an iris cyst in the contralateral eye after 3 years. All owners reported improvement in clinical signs, with 61% reporting no further signs.

STAPIC is an effective and easily accessible alternative for treating iris cysts in horses rarely associated with complications.