Evaluating the effect of pulse energy on femtosecond laser trabeculotomy (FLT) outflow channels for glaucoma treatment in human cadaver eyes

Background and Objectives: Femtosecond laser trabeculotomy (FLT) creates aqueous humor outflow channels through the trabecular meshwork (TM) and is an emerging noninvasive treatment for open-angle glaucoma. The purpose of this study is to investigate the effect of pulse energy on outflow channel creation during FLT. Materials and Methods: An FLT laser (ViaLase Inc.) was used to create outflow channels through the TM (500 mu m wide by 200 mu m high) in human cadaver eyes using pulse energies of 10, 15, and 20 mu J. Following treatment, tissues were fixed in 4% paraformaldehyde. The channels were imaged using optical coherence tomography (OCT) and assessed as full thickness, partial thickness, or not observable. Results: Pulse energies of 15 and 20 mu J had a 100% success rate in creating full-thickness FLT channels as imaged by OCT. A pulse energy of 10 mu J resulted in no channels (n = 6), a partial-thickness channel (n = 2), and a full-thickness FLT channel (n = 2). There was a statistically significant difference in cutting widths between the 10 and 15 mu J groups (p < 0.0001), as well as between the 10 and 20 mu J groups (p < 0.0001). However, there was no statistically significant difference between the 15 and 20 mu J groups (p = 0.416). Conclusions: Fifteen microjoules is an adequate pulse energy to reliably create aqueous humor outflow channels during FLT in human cadaver eyes. OCT is a valuable tool when evaluating FLT.