Investigation of Corneal Endothelial Changes Post Selective Laser Trabeculoplasty

Abstract

Purpose: Subtle changes in the corneal endothelium have been observed clinically immediately post selective laser trabeculoplasty (SLT). The purpose of this study was to further characterize these changes.

Methods: Confocal microscopy imaging of human cadaveric donor corneas mounted on an artificial anterior chamber (n = 3) in response to direct application of laser, dilute blood (10%), or weak hydrogen peroxide (200 μmol/L) was undertaken to mimic potential conditions which describe the clinical finding. An additional eight corneas from four donors were mounted in artificial anterior chambers filled with balanced saline solution (BSS). Four corneas were treated with SLT using a Nd:YAG laser (Ellex Tango, Adelaide Australia) through either 90 degrees (30 shots), 180 degrees (60 shots) or 360 degrees (120 shots) of the peripheral cornea (laser power 0.9 mJ). Contralateral corneas from the same donor were used as controls. Vertical sections were examined for cellular morphology (H&E) and tight junctions (ZO-1 immunostaining). Transverse sections through the endothelium of corneas stained for ZO-1 were examined using confocal microscopy.

Results: Direct laser produced a circular region of endothelial destruction surrounded by increased endothelial blebs. A different cornea exposed to blood showed increased reflectivity indicative of protein deposition. The cornea exposed to weak peroxide showed widening of intercellular spaces. H&E sections did not show pigment or protein deposition on the endothelial surface. Immunofluorescent staining for ZO-1 showed an even staining pattern across the endothelium in control corneas and a granular appearance in corneas treated with SLT. The response appeared dose-dependent, with more interruptions in ZO-1 immunostaining of corneas treated with SLT through a wider degree of periphery. All treatments other than direct laser produced changes that were generalized across the entire corneal endothelium.

Conclusions: The endothelial changes observed after SLT can be mimicked with a combination of weak blood solution and dilute hydrogen peroxide. A less even distribution of ZO-1 immunostaining was observed after SLT treatment, which may represent disassembly of tight junctions between endothelial cells.

Keywords: 481 cornea: endothelium • 578 laser • 446 cell adhesions/cell junctions