Comparison of morphologic changes after continuous and micro-pulse yellow laser trabeculoplasty by scanning electron microscopy Wingard JB; Miller KV; Pokabla MJ; Strunk KM; Gray JL; Bentivegna R; Noecker RJ The authors of this poster received research funding from Research to Prevent Blindness and the National Institutes of Health. UPMC Eye Center, Department of Ophthalmology University of Pittsburgh School of Medicine Ophthalmology & Visual Science Research Center The Eye & Ear Institute

PURPOSE To examine the morphologic trabecular meshwork (TM) changes resulting from a range of power settings for micro-pulse yellow laser trabeculoplasty (MYLT), in comparison to continuous yellow laser trabeculoplasty (CYLT).

METHODS Direct laser treatment of the TM of human cadaver eyes. Iridex IQ577 laser (wavelength 577 nm) was used for all applications. Six distinct regions were treated with either continuous or micro-pulse laser, employing multiple, non-overlapping laser spots for each treatment in the table that follows (next slide), encompassing CYLT and a range of MYLT power setting. The eyes were preserved in glutaraldehyde and phosphate- buffered saline. Scanning electron microscopy was performed on each section to image morphologic changes due to the laser treatments.

TREATMENT PARAMETERS

RESULTS A range of morphologic changes was observed in the treated samples. Continuous laser produced craters and extensive coagulative damage to the TM. At higher energies, micro-pulse laser at a 15% duty cycle showed coagulative damage. At lower energies, micro-pulse treated samples were indistinguishable from untreated controls.

Continuous laser treatment Distinct crater formation is demonstrated with continuous yellow laser trabeculoplasty. * = craters

Micro-pulse treatment, 2000 mW Micro-pulse yellow laser trabeculoplasty 2000 mW shows areas of coagulative damage but no crater formation. * = zone of coagulative damage

Micro-pulse treatment, 1000 mW There is no discernible difference between trabecular meshwork treated with micro- pulse yellow laser trabeculoplasty at the 1000 mW setting and untreated control TM. Untreated control

CONCLUSIONS Morphologic evaluation of cadaver eyes after micro-pulse yellow laser trabeculoplasty (MYLT) demonstrates limited damage to the trabecular meshwork in comparison to eyes treated with continuous laser energy. MYLT, utilizing 100-microsecond pulses to lower the total energy delivered, may be a less destructive alternative for laser trabeculoplasty due to decreased thermal damage.