Diode laser endoscopic cyclophotocoagulation in the normal equine eye

Area of Science:

• Ophthalmology
• Veterinary Medicine
• Surgical Innovation

Background:

• Glaucoma is a leading cause of blindness in horses.
• Endoscopic cyclophotocoagulation (ECP) is a potential treatment for glaucoma by reducing aqueous humor production.
• The efficacy and safety of diode ECP in the phakic equine eye require further investigation.

Purpose of the Study:

• To evaluate the clinical and histologic effects of diode ECP in equine eyes.
• To determine optimal energy levels for ECP in horses.
• To assess potential complications of ECP in phakic equine eyes.

Main Methods:

• Phase I involved cadaver eyes to determine probe reach and evaluate tissue response to varying ECP energy levels.
• Phase II utilized live horses, treating ocular quadrants with ECP and comparing to a sham-controlled contralateral eye.
• Histologic and clinical assessments were performed to evaluate tissue damage and treatment effects.

Main Results:

• ECP at all tested energy levels caused ciliary tissue damage.
• Visible tissue damage scores increased with energy levels, with 'popping' observed at higher settings (1.50 J and 1.38 J).
• Clinical effects included inflammation, reduced intraocular pressure, and adverse events like cataract formation and corneal ulceration.

Conclusions:

• Diode ECP at 0.90-1.14 J demonstrates potential for equine glaucoma treatment due to ciliary epithelium damage.
• Iatrogenic cataract development is a significant concern, potentially limiting anterior chamber ECP in phakic horses.
• Further research is needed to refine ECP techniques and mitigate risks in equine patients.