Feasibility of aqueous shunts for reduction of intraocular pressure in horses

Authors


  • Presented in part in abstract form at the 4th Annual Conference of the International Equine Ophthalmology Consortium, Stirling, Scotland, June, 2012.

Summary

Reasons for performing study

Based on the current literature, neither medical, surgical nor combination therapy adequately controls equine glaucoma for many horses. Aqueous shunts have been useful in other species to control glaucoma.

Objectives

To determine whether aqueous shunts in normal equine eyes significantly reduce intraocular pressure (IOP) without causing vision threatening complications.

Study design

Prospective experimental trial.

Methods

Aqueous shunts were placed in 7 normal eyes of 4 horses. The shunts were placed dorsotemporally. Examinations were initially performed daily for 7 days and after that every 3 days through 4 weeks after implantation. Horses were then subjected to euthanasia and globes enucleated for routine histological examination. The IOPs for each day post operatively were compared to the preoperative value (Day -1) using a Wilcoxon signed ranks test. Significance was set at P<0.05.

Results

The mean IOP preoperatively (20.7 ± 3.0 mmHg) was significantly higher than on any post operative day (P values ranged from 0.018 to 0.048). The aqueous shunts remained in situ for the entire study. Two eyes developed corneal ulcers that resolved. Shallow anterior chambers were noted in 2 eyes after shunt placement, which normalised after placement of full eye cup masks. Histologically, 7/7 eyes had fibrosis surrounding the implant. Minimal peripheral neovascularisation and neutrophilic keratitis were noted in 5/7 eyes. Corneal damage was scored as none in 3/7, mild in 2/7, moderate in 1/7 and marked in 1/7 eyes.

Conclusions

After placement of aqueous shunts, a significant decrease in IOP was noted from preoperatively (Day -1) to Day 28 despite fibrosis surrounding the implants. No vision threatening complications were noted.

Potential relevance

Aqueous shunts may represent a feasible therapeutic option for equine glaucoma. The results of this study suggest that further studies in glaucomatous horses would be warranted.

The Summary is available in Chinese – see Supporting information.

Ancillary