The long-term effects of semiconductor diode laser transscleral cyclophotocoagulation on the normal equine eye and intraocular pressure(a).

The research article explores the long-term results and impacts on eye pressure following a diode laser treatment, known as transscleral cyclophotocoagulation (TSCP), on the normal eyes of horses.

Methods

• The researchers performed TSCP on randomly selected eyes of eight adult horses. Out of the total of sixty spots treated with specific settings, two horses were chosen randomly to be euthanized at different intervals after the procedure (2, 4, 12, or 24 weeks).
• After the horses were euthanized, their eyes were enucleated (or removed) and then thoroughly examined in a histological study.
• Intraocular pressure (IOP), the fluid pressure inside the eye, was measured via a process called applanation tonometry before and after the TSCP procedure, twice a day for a week after TSCP, and monthly until the end of the study.
• The estimated average IOP values at various time points post-TSCP for both the treated and untreated eyes were calculated using a longitudinal model.

Results

• The histologic evaluation revealed four evident lesions or damages in all treated eyes post-TSCP: (1) scleral collagen hyalinization, or the hardening of the collagen in the eye wall; (2) dispersion and clumping of the ciliary body pigment, which could affect the eye’s focus; (3) focal disruption of the ciliary body epithelium that aids in maintaining the eye’s pressure; (4) focal ciliary process atrophy- decrease in the size of ciliary process, which produces the fluid in the eyes.
• Post TSCP, the IOP values for the control eyes showed no significant changes, whereas the treated eyes indicated a considerable reduction. All these reductions were statistically proven to be significant (P < 0.05).
• The average reduction in IOP, six months following treatment, was calculated to be -3.76 mmHg, which indicates a drop of 20% from the initial pressure.

Conclusions

• The results highlight that diode laser TSCP results in recognizable lesions in the equine ciliary body and leads to a significant and prolonged decrease in Intraocular Pressure.
• Therefore, the researchers concluded that TSCP could potentially serve as an effective treatment for equine glaucoma, a condition characterized by elevated intraocular pressure that may harm the horse’s optic nerve and result in vision loss.