Evaluation of circumferential angle closure using iridotrabecular contact index after laser iridotomy by swept-source optical coherence tomography

초록

PurposeTo investigate the quantitative changes of circumferential angle closure after laser iridotomy (LI) using the iridotrabecular contact (ITC) index by Swept-Source optical coherence tomography (OCT). MethodsIn this prospective observational study conducted in a hospital setting, 42 eyes of 36 patients (five males, 31 females) who underwent LI were included. The mean age was 65.008.13years old and the diagnosis included primary angle closure (PAC, 21 eyes), PAC suspect (16 eyes) and PAC glaucoma (five eyes). Optical coherence tomography (OCT) images were obtained pre-LI and at 1week post-LI. In each image frame, the scleral spur (SS) and the ITC end-point were marked, from which the ITC index was calculated as a percentage of the angle closure across 360 degrees. Measurements inspected before and after LI included: central anterior chamber depth (ACD), anterior chamber volume (ACV), lens vault (LV), nasal and temporal angle opening distance (AOD), angle recess area (ARA), trabecular-iris space area (TISA), trabecular-iris angle (TIA) at 500m and 750m from the SS and intraocular pressure (IOP). ResultsThe ITC index and IOP decreased significantly after LI from 71.52 +/- 26.29 to 35.31 +/- 27.19 and from 20.64 +/- 12.72mmHg to 14.02 +/- 3.49mmHg, respectively (p<0.001 and p<0.001). Central ACD (1.94 +/- 0.31mm pre-LI) and LV (1.13 +/- 0.32mm pre-LI) did not show a significant change after LI (all p>0.05), but ACV increased significantly after LI (p<0.001). Most of the angle parameters except for nasal TIAs increased significantly after LI (all p<0.05). ConclusionThe ITC index from patients with shallow anterior chamber angle showed a significant decrease after LI, but part of the angle closure was not relieved after LI. Other mechanisms besides pupillary block may play a role together in causing angle closure.

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