Feasibility of aqueous shunts for reduction of intraocular pressure in horses.

Authors: Townsend W M, Langohr I M, Mouney M C, Moore G E

Journal: Equine veterinary journal

DOI: 10.1111/evj.12098 PubMed: 23662686Log in to save

Summary

# Aqueous Shunts for Equine Glaucoma: A Feasibility Study Equine glaucoma remains notoriously difficult to manage, with existing medical and surgical treatments often failing to adequately control intraocular pressure (IOP) in affected horses, prompting investigation into techniques successfully used in other species. Researchers implanted aqueous shunts in seven normal equine eyes and monitored IOP reduction and tissue responses over four weeks post-operatively, examining both clinical signs and histological changes following euthanasia. Mean preoperative IOP of 20.7 ± 3.0 mmHg decreased significantly on every post-operative day (P = 0.018–0.048), with all shunts remaining in place throughout the study period, though fibrosis developed around every implant and corneal damage varied from absent to marked. Minor complications including transient corneal ulceration and shallow anterior chambers resolved with conservative management, and crucially, no vision-threatening sequelae were observed. Whilst this feasibility work in normal eyes demonstrates IOP reduction is achievable without severe ocular damage, clinical application in glaucomatous horses requires further evaluation to determine whether pressure control translates to functional outcomes and whether the observed fibrotic response might eventually limit shunt efficacy.

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Practical Takeaways

•Aqueous shunts effectively lower IOP in normal equine eyes and warrant investigation as a potential treatment for equine glaucoma when medical/surgical options fail
•Early postoperative management should include monitoring for corneal complications and anterior chamber shallowing, with eye cup masks available as a supportive intervention
•Implant fibrosis is an expected finding that does not prevent sustained IOP reduction, but long-term safety and efficacy in naturally glaucomatous horses remains to be established

Key Findings

•Mean IOP decreased significantly from 20.7 ± 3.0 mmHg preoperatively to lower values on all postoperative days (P = 0.018–0.048)
•All 7 aqueous shunts remained in situ throughout the 28-day study period
•Fibrosis surrounded all implants histologically, with minimal peripheral neovascularization and neutrophilic keratitis in 5/7 eyes
•Two eyes developed transient corneal ulcers that resolved; two eyes developed shallow anterior chambers that normalized with eye cup masks

Conditions Studied

glaucomaelevated intraocular pressurecorneal ulcersanterior chamber depth abnormalities

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