title: Association between baseline iris thickness and prophylactic laser peripheral iridotomy outcomes in primary angle-closure suspects.
abstract: OBJECTIVE
  To evaluate the association between baseline measurements of iris thickness at 3 positions and change in anterior segment biometric parameters after prophylactic laser peripheral iridotomy (LPI).
  
  
  METHODS
  Prospective clinical cohort study.
  
  
  METHODS
  Fifty-two eyes of 52 nonglaucomatous subjects with anatomically narrow angles.
  
  
  METHODS
  Anterior segment optical coherence tomography (ASOCT) images captured before and after LPI were analyzed using customized software, the Zhongshan Angle Assessment Program (ZAAP) (Zhongshan Ophthalmic Centre, Guangzhou, China). Differences in preoperative and postoperative measurements for anterior segment biometric parameters were compared by paired Student t tests. Multivariate linear regression models, adjusted for age, sex, ethnicity, and preoperative pupil diameter, were used to examine the association between the baseline measurements of iris thickness at 3 positions and the change in anterior segment biometric parameters after LPI.
  
  
  METHODS
  Baseline iris thickness measured at 750 μm from the scleral spur (IT750), iris thickness measured at 2000 μm from the scleral spur (IT2000), and maximal iris thickness (ITM). Changes in iris curvature (ICURV) and trabecular-iris space area at 500 μm from the scleral spur (TISA500) and 750 μm from the scleral spur (TISA750) after LPI.
  
  
  RESULTS
  The ICURV significantly decreased, whereas TISA500 and TISA750 significantly increased after LPI (all P < 0.0001). Lower baseline IT750 was significantly associated with greater postoperative increases in TISA500 and TISA750 (both P < 0.05). Lower baseline IT2000 and ITM were significantly associated with greater postoperative decrease in ICURV (both P < 0.05).
  
  
  CONCLUSIONS
  Our results showed that lower baseline measurements of iris thickness are associated with greater decrease in ICURV and increases in TISA500 and TISA750 after LPI. This suggests that eyes with thinner irides undergoing LPI were more likely to exhibit greater magnitude of change in terms of flattening of the iris convexity (i.e., ICURV) and widening of the anterior chamber angle (i.e., TISA500 and TISA750).
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, California.
authors.forename: Roland Y
authors.initials: RY
authors.lastname: Lee
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, California; Department of Ophthalmology, Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Kasuga
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, California.
authors.forename: Qi N
authors.initials: QN
authors.lastname: Cui
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, California.
authors.forename: Travis C
authors.initials: TC
authors.lastname: Porco
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, California; Department of Ophthalmology, Nanchang University, Nanchang, Jiangxi Province, China.
authors.forename: Guofu
authors.initials: G
authors.lastname: Huang
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, California; State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yatsen University, Guangzhou, China.
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, California. Electronic address: LinS@vision.ucsf.edu.
authors.forename: Shan C
authors.initials: SC
authors.lastname: Lin
mesh_terms: D000368:Aged; D001699:Biometry; D015331:Cohort Studies; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D032801:Iridectomy / Q000379:methods*; D007498:Iris / Q000473:pathology* / Q000601:surgery; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D008297:Male; D009929:Organ Size; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D016896:Treatment Outcome; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology