The Effects of Lasers on Outflow Structures

Abstract

The morphological effect of trabeculoplasty upon the monkey eye was studied by electron microscopy. Irradiations were performed using the argon-ion and the free-running Nd: YAG lasers. Morphological analysis up to thirteen weeks after irradiation shows the following:

• 1. A thermal coagulation of the inner trabecular sheets occurs during irradiation.

• 2. A monolayer of corneal-like endothelial cells covers the inner trabecular meshwork in the impact zone four weeks after irradiation.

• 3. Degeneration of trabecular endothelial cells is observed predominantly in the juxtacanalicular tissue. The process continues throughout the period of observation.

• 4. Cells with long processes are found to phagocytose and digest fragments of collagen fibrils. These cells are located close to the posterior border of Schlemm’s canal and are most prominent during the later stages of observation.

• 5. Alongside the degeneration process a limited collagen synthesis is apparent, this being indicated by the presence of a small number of fibroblasts.

These findings suggest that new aspects relating to the mechanism of trabeculoplasty may have to be considered.

This work was supported by the Swiss National Science Foundation, grant number 3.872-0.83, and the Swiss Commission for the Promotion of Scientific Research.