Histologic effect of semiconductor diode laser transscleral cyclophotocoagulation on the normal equine eye.

The study reports on the effects that a specific kind of laser surgery called “transscleral cyclophotocoagulation” (TSCP) has on horse eyes. It concludes that performing this surgery at a specific distance from certain points on the eye, and setting the laser at a particular energy level, leads to effective treatment of a specific part of the eye, while avoiding serious complications.

Methodology

The research took place in two parts, using either four horses (eight eyes) in the first part, and five horses (ten eyes) for the second part. Specific procedures for each part were:

• In Part 1: TSCP was performed on eight eyes, four at 4mm and four at 6mm from a certain point in the eye. Each eye received 15 treatments across four quadrants for a set duration. The eyes were then cut apart for examination and each part of the globe was examined using thin tissue sections.
• In Part 2: Based on the results of Part 1, TSCP was performed with varying energy levels on 20 sites that were 4mm from another specific point within the eye. After the procedure, sections of each eye were taken for examination.

Findings

Beefing up the robustness of the study, results were reported from both the first and second phase:

• In Part 1: At 4mm from the set point on the eye, coagulation was seen in certain parts of the eye and certain issues like retinal detachment and hemorrhage were noticed in other quadrants at a particular frequency. At 6mm from the set point, a similar pattern was seen but with slightly different frequencies.
• In Part 2: The energy settings of the TSCP procedure were recorded. It was seen that the lowest setting was ineffective, while other settings caused damage to the pars plicata without causing disruption to the eye’s anatomy. However, the highest setting did result in disruption to the eye’s normal structure.

Conclusions

Based on findings from both parts of the study, the researchers concluded that for horses undergoing TSCP, the procedure should be performed at 4mm from the dorso- and ventrotemporal limbus part of the equine eyes, avoiding certain positions, and set at an energy level of 2.25 J/site. The researchers believe this method provides effective treatment of the pars plicata, while minimizing potentially serious surgical complications, such as retinal detachment and hemorrhage.