Characterization of Peripheral Anterior Synechiae Formation After Microhook Ab-interno Trabeculotomy Using a 360-Degree Gonio-Camera

PURPOSE: To investigate the prevalence, locations, and characteristics of peripheral anterior synechiae (PAS) formation after microhook ab-interno trabeculotomy (µLOT), a minimally invasive glaucoma surgery, using a 360-degree gonio-camera, gonioscope GS-1 (NIDEK Co., Gamagori, Japan). SUBJECTS AND METHODS: A total of 105 consecutive eyes of 75 subjects with open-angle glaucoma were analyzed. The eyes had undergone µLOT or combined µLOT and cataract surgery as an initial glaucoma surgery. Postoperative PAS formation was evaluated in 16 iridocorneal angle images with the best focus covering 360 degrees in each eye. RESULTS: Compared to baseline, at 225±226 days postoperatively, the intraocular pressure and number of antiglaucoma medications decreased significantly (p<0.01, respectively). PAS developed in 86% of eyes. The mean number of iridocorneal angle images that showed PAS in all eyes was 4.1 (26%) in the total circumference, 3.1 (39%) within the µLOT incision, and 1.0 (13%) outside of the µLOT incision; the rate was significantly (p<0.0001) higher within the incision than outside of the incision. Moreover, the higher total PAS rate and that within the incision may be associated with later postoperative days (p=0.01 and 0.004, respectively), that outside of the incision with µLOT alone rather than the combined surgery, and with shallower preoperative central anterior chamber depth (p=0.048 and 0.04, respectively), calculated by the mixed-effect model. CONCLUSION: The current results showed the characteristics of PAS formation after µLOT using 360-degree gonio-images, and the formation rate was significantly higher within the µLOT incision. The PAS within and outside of the incision had different causes.