title: Evaluation of circumferential angle closure using iridotrabecular contact index after laser iridotomy by swept-source optical coherence tomography.
abstract: OBJECTIVE
  To 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).
  
  
  METHODS
  In 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 65.00 ± 8.13 years 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 1 week 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°. 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 500 μm and 750 μm from the SS and intraocular pressure (IOP).
  
  
  RESULTS
  The ITC index and IOP decreased significantly after LI from 71.52 ± 26.29 to 35.31 ± 27.19 and from 20.64 ± 12.72 mmHg to 14.02 ± 3.49 mmHg, respectively (p < 0.001 and p < 0.001). Central ACD (1.94 ± 0.31 mm pre-LI) and LV (1.13 ± 0.32 mm 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).
  
  
  CONCLUSIONS
  The 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.
authors: Department of Ophthalmology, Gyeongsang National University Changwon Hospital, School of Medicine, Gyeongsang National University, Changwon, Korea.
authors: Hyun-Kyung
authors: HK
authors: Cho
authors: Department of Ophthalmology, Sungmo Eye Hospital, Busan, Korea.
authors: Dongsub
authors: D
authors: Ahn
authors: Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors: Changwon
authors: C
authors: Kee
mesh_terms: D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D006068:Gonioscopy / Q000379:methods; D006801:Humans; D007429:Intraocular Pressure; D032801:Iridectomy / Q000379:methods*; D007498:Iris / Q000000981:diagnostic imaging* / Q000601:surgery; D053685:Laser Therapy / Q000379:methods*; D008297:Male; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D014129:Trabecular Meshwork / Q000000981:diagnostic imaging*
keywords: angle closure; anterior segment optical coherence tomography; laser iridotomy; peripheral angle