Clinical and Histopathological Evaluation of Maximal and Supramaximal Energy Direct Selective Laser Trabeculoplasty (DSLT): A Rabbit Model Safety Study

OBJECTIVES: This study aimed to assess the clinical and histopathological effects of maximal available and supramaximal energy exposure in direct selective laser trabeculoplasty (DSLT®) on target and nontarget ocular tissues compared with selective laser trabeculoplasty (SLT) and sham treatments. MATERIALS AND METHODS: Thirty eyes of 16 Dutch Belted Rabbits were allocated into seven groups: (A) Maximal energy DSLT exposure (2.6 mJ), (B) supramaximal energy DSLT exposure (3.5 mJ) with double nominal density spot spacing, (C and D) nontarget DSLT on sclera and iris at maximal and supramaximal energy, (E) SLT treatment at maximal energy (2.6 mJ), (F) SLT treatment with two overlapping shots at maximal energy (2.6mJ), and (G) sham control. The eyes were examined using a biomicroscope slit lamp, anterior segment OCT (AS-OCT), and a specular microscope at baseline, Day 1, and Weeks 1, 2, and 4 post-treatments. Histopathological evaluation was conducted on eyes enucleated on Days 1 and 29 posttreatment. The study was conducted at the Harlan laboratory, Ness-Ziona, Israel. RESULTS: All DSLT and SLT laser treatments were uneventful. Minor acute responses were observed 1-day posttreatment at the slit lamp biomicroscopy exam, with similar DSLT and SLT responses. No significant clinical or histopathological findings were observed in any treatment groups at 29 days posttreatment. No notable findings indicative of damage to nontarget tissues were noted, including damage to the limbal stem cells. CONCLUSION: DSLT treatment at the limbus, iris, and sclera yielded no significant clinical or histopathological changes compared to SLT or sham eyes, even with supramaximal energy and double-density exposures.