Noninvasive diode laser–an effective and safe treatment of iris cysts in 46 eyes of 35 horses

Abstract

Background: Iris cysts in horses are often asymptomatic and noticed incidentally.However, cysts can cause local corneal oedema and erratic behaviour like shying, decreased performance and head-shaking.Objectives: To describe the use of diode laser as a noninvasive treatment option for iris cysts in the horse and to document factors influencing its efficacy, associated complications, long-term outcome and rate of recurrence. Study design: Retrospective case series. Methods: Case records of horses treated for iris cysts by diode laser at the Utrecht University Equine Clinic were reviewed between 2008 and 2020. Diagnosis was based on ophthalmic and ultrasonographic evaluation. Long-term follow-up was obtained in two phases, a telephone survey with the owner and a photographic reevaluation of the treated eyes.Results: Thirty-five horses were included, with a total of 46 eyes treated. One day after diode laser treatment (short-term), 35/46 treated eyes had a good decrease in cyst size, 7/46 had a moderate effect, 1/46 had a minimal effect, 1/46 had no effect, and in two cases the effect was unspecified. The decrease in size after diode laser treatment in polycystic eyes (odds ratio [OR] 0.381, 95% CI 0.1530-0.724), p = 0.001), thick-walled cysts (OR = 0.139; CI = 0.023-0.726, p = 0.02) and hyperplastic corpora nigra (OR = 0.081; CI = 0.004-0.528, p = 0.03) was significantly less satisfactory, with ORs of 0.381, 0.139 and 0.081, respectively. Minor complications, such as mild reactive uveitis, were reported in 8/46 (17%) eyes. On long-term follow-up (median 19 months; IQR 25.5), clinical signs had diminished or disappeared in most cases (93%) and 83% of the owners would recommend the treatment. Based on long-term photographic re-evaluation (median 32.5 months; IQR 49.75), 2/16 cases of recurrence were seen.Main limitations: Retrospective design, follow-up by telephone questionnaire and photographic re-evaluation. Loss to follow-up in the photographic re-evaluation.Conclusions: Both short-and long-term results indicate diode laser treatment is a useful and safe option for iris cyst size reduction, with a low risk of recurrence.

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

“…Ultrasound is reported to rarely be required as iris cysts have a very characteristic appearance (Gilger et al., 2022 ); however, Stas et al. ( 2023 ) reported that ultrasound prior to treatment aided in evaluating the number of cysts and their appearance including the size, architecture and wall thickness. They found this to be useful information to determine treatment success rates and surgical planning when using a diode laser.…”

“…Equine primary iris cysts are smooth, often focal swellings that are darker than the iris and usually attached to the pupillary margin, arising from the inner non‐pigmented ciliary body epithelium (Dziezyc et al., 1990 ; Shields et al., 1984 ). They are often an incidental finding in the horse but have been reported to cause behavioural changes including spooking, poor performance often associated with jumping and headshaking (Berger et al., 2008 ; Stas et al., 2023 ). Occasionally, they have been reported to contact the corneal endothelium, leading to oedema formation with recurrent corneal ulceration (Byam‐Cook & Knottenbelt, 2007 ; Stas et al., 2023 ).…”

“…They are often an incidental finding in the horse but have been reported to cause behavioural changes including spooking, poor performance often associated with jumping and headshaking (Berger et al., 2008 ; Stas et al., 2023 ). Occasionally, they have been reported to contact the corneal endothelium, leading to oedema formation with recurrent corneal ulceration (Byam‐Cook & Knottenbelt, 2007 ; Stas et al., 2023 ). Theoretically, they can also affect aqueous humour flow, although secondary glaucoma has not been reported in horses (Gemensky‐Metzler et al., 2004 ; Gilger et al., 1997 ; Stas et al., 2023 ).…”

“…Occasionally, they have been reported to contact the corneal endothelium, leading to oedema formation with recurrent corneal ulceration (Byam‐Cook & Knottenbelt, 2007 ; Stas et al., 2023 ). Theoretically, they can also affect aqueous humour flow, although secondary glaucoma has not been reported in horses (Gemensky‐Metzler et al., 2004 ; Gilger et al., 1997 ; Stas et al., 2023 ).…”

“…The current recommended treatment is transcorneal ablation to deflate the cyst using a diode, argon or neodymium–yttrium aluminium garnet (Nd:YAG) laser utilising standing sedation. Multiple case series have reported successful treatment with minimal complications (Gemensky‐Metzler et al., 2004 ; Lam & Pumphrey, 2021 ; Stas et al., 2023 ; Tóth & Buijs, 2018 ). Successful treatment of iris cysts using transcorneal fine needle aspiration has been reported under general anaesthesia in a range of species (Byam‐Cook & Knottenbelt, 2007 ; Delgado et al., 2010 ; Georgalas et al., 2018 ).…”