title: Changes in anterior segment morphology after laser peripheral iridotomy: an anterior segment optical coherence tomography study.
abstract: OBJECTIVE
  Novel anterior segment optical coherence tomography (ASOCT) parameters associated with angle closure include anterior chamber area (ACA), anterior chamber volume (ACV), anterior chamber width (ACW), lens vault (LV), iris thickness (IT), iris area (I-area), and iris curvature (I-curv). We aimed to investigate changes in these parameters after laser peripheral iridotomy (LPI) in a cohort of primary angle-closure suspects (PACS).
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  A total of 176 PACS aged ≥ 50 years who underwent LPI in 1 eye.
  
  
  METHODS
  We analyzed ASOCT images (Visante, Carl Zeiss Meditec, Dublin, CA) from all subjects using customized software before and 1 week after LPI. Multivariate linear regression analysis was performed for predictors of percentage change in mean angle opening distance (AOD750).
  
  
  METHODS
  Change in ASOCT parameters after LPI.
  
  
  RESULTS
  The mean age of participants was 63 ± 7.3 years. The majority of subjects were Chinese (95.5%) and women (76.7%). Mean angle width (modified Shaffer grade) changed from 0.68 ± 0.54 at baseline to 1.76±0.69 after LPI (P<0.001) with a corresponding increase in mean AOD500 (0.12 vs. 0.19 mm, P<0.001), trabecular iris surface area (TISA500, 0.06 vs. 0.08 mm(2), P<0.001), and angle recess area (ARA, 0.13 vs. 0.17 mm(2), P<0.001). Mean ACA (15.0 vs. 16.0 mm(2), P<0.001) and ACV (91.6 vs. 103.0 mm(3), P<0.001) increased significantly after LPI, but there was no change in ACW, anterior chamber depth (ACD), or LV. Mean I-curv was reduced (0.375 vs. 0.18 mm, P<0.001) after LPI, but there was no significant change in IT or I-area. After multivariate analysis, mean LV (β = 0.286, P = 0.001), mean IT at 2000 μm (IT2000, β = 0.172, P = 0.034), and intraocular pressure (β = 0.159, P = 0.042) at baseline were found to be associated with ΔAOD750.
  
  
  CONCLUSIONS
  This study confirms that LPI results in a significant increase in the angle width in PACS. The ACA and ACV increased after LPI, but there was no change in ACD, ACW, LV, IT, or I-area. The increase in ACA/ACV was mainly due to decreased I-curv after LPI.
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Center, Singapore.
authors.forename: Alicia C
authors.initials: AC
authors.lastname: How
authors.forename: Mani
authors.initials: M
authors.lastname: Baskaran
authors.forename: Rajesh S
authors.initials: RS
authors.lastname: Kumar
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Foster
authors.forename: Raghavan
authors.initials: R
authors.lastname: Lavanya
authors.forename: Hon-Tym
authors.initials: HT
authors.lastname: Wong
authors.forename: Paul T K
authors.initials: PT
authors.lastname: Chew
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
mesh_terms: D000869:Anterior Eye Segment / Q000473:pathology*; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000503:physiopathology / Q000517:prevention & control*; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D032801:Iridectomy; D007498:Iris / Q000601:surgery; D053685:Laser Therapy; D053844:Lasers, Solid-State / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D014792:Visual Acuity / Q000502:physiology; D014794:Visual Fields / Q000502:physiology