Morphologic and Cellular Changes Induced by Selective Laser Trabeculoplasty

PURPOSE: Selective laser trabeculoplasty is a safe and effective procedure for reducing IOP, but its mechanism of action is not fully elucidated. We evaluated the morphologic and cellular changes as well as DNA synthesis after SLT treatment of human trabecular meshwork (TM) tissue explants. METHODS: Corneoscleral rim tissues that underwent SLT treatment were compared to control segments that had no laser treatment. Light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to assess cell morphology. The Click-iT 5-ethynyl-2’-deoxyuridine (EdU) imaging kit was used to compare DNA synthesis/cell proliferation with a confocal microscope. All tissues were assessed for vitality. RESULTS: SLT treatment does not reveal notable cell damage in the juxtacanalicular (JCT) region, but mildly disrupts superficial trabecular beams and uveal TM, ablates TM endothelial cells from the undamaged beams as detected by both LM and TEM. This superficial destruction was not observed in some SLT treatment spots on higher magnification by SEM. SLT treatment increased mitotic activity and DNA synthesis near the lining of Schlemm’s canal after several days. CONCLUSION: SLT treatment disrupts endothelial cells in the corneoscleral TM and causes superficial ultrastructural changes to the uveal TM. SLT treatment also shows a trend towards dynamic time-dependent changes in (DNA synthesis) with an increase in mitotic activity at 7 days cell proliferation.