Delayed response to argon laser trabeculoplasty in monkeys. Morphological and morphometric analysis

Area of Science:

• Ophthalmology
• Cell Biology
• Medical Imaging

Background:

• Argon laser trabeculoplasty (ALT) is a common glaucoma treatment.
• The precise cellular and structural responses of the trabecular meshwork (TM) to ALT are not fully understood.
• Understanding TM morphology post-ALT is crucial for evaluating treatment efficacy and potential side effects.

Purpose of the Study:

• To investigate the morphological changes in the trabecular meshwork (TM) following argon laser trabeculoplasty (ALT) in cynomolgus monkeys.
• To elucidate the biological processes underlying the TM's response to laser treatment.
• To analyze the structural alterations in both lasered and adjacent non-lasered TM areas.

Main Methods:

• Eight cynomolgus monkeys underwent argon laser trabeculoplasty.
• Trabecular meshwork (TM) morphology was evaluated four weeks post-treatment.
• Statistical morphometric analysis was performed on samples from three monkeys, comparing treated and control eyes.

Main Results:

• Treated spots showed flattened, collapsed beams covered by a cellular sheet, with a flat inner wall of Schlemm's canal.
• Adjacent non-lasered spots exhibited wider intertrabecular spaces with herniations of TM and endothelium into Schlemm's canal.
• These herniations contained inflammatory cells and vacuoles, and were significantly more numerous and wider in treated eyes compared to controls.

Conclusions:

• Argon laser trabeculoplasty (ALT) induces scarring and obliteration of treated TM spots.
• A biological process redirects aqueous humor flow to adjacent non-lasered TM regions.
• This diversion causes significant structural alterations, including herniations and inflammation, in non-treated areas, potentially impacting long-term efficacy.