title: Light-dark changes in iris thickness and anterior chamber angle width in eyes with occludable angles.
abstract: BACKGROUND
  The purpose of this study was to investigate and measure light-dark changes in iris thickness (IT) and anterior chamber angle width in eyes with occludable angles and open angles by using anterior segment optical coherence tomography (AS-OCT).
  
  
  METHODS
  We examined 153 eyes of 153 Japanese patients with primary angle closure suspect, primary angle closure, primary angle closure glaucoma, or primary open angle glaucoma. AS-OCT was used to determine pupil diameter, IT, angle opening distance at 500 μm (AOD₅₀₀), and trabecular-iris space area at 500 μm (TISA₅₀₀) in each quadrant of the anterior chamber angle (superior, inferior, temporal, and nasal) under light and dark conditions.
  
  
  RESULTS
  In the angle closure cases, IT, AOD₅₀₀ and TISA₅₀₀ in the dark varied significantly among the four quadrants (P < 0.05, analysis of variance). In contrast, in the open angle cases, IT, AOD₅₀₀ and TISA₅₀₀ in the dark did not differ significantly among the four quadrants. In the angle closure cases and the open angle cases, significant negative associations were found between IT difference [IT(light)-IT(dark)] and AOD₅₀₀ difference [AOD₅₀₀(light)-AOD₅₀₀(dark)] (R = -0.411, P < 0.001 and R = -0.501, P = 0.001, respectively) and between IT difference and TISA₅₀₀ difference [TISA₅₀₀(light)-TISA₅₀₀(dark)] (R = -0.475, P < 0.001 and R = -0.462, P = 0.002, respectively).
  
  
  CONCLUSIONS
  Our results suggest that thickening of the iris root under dark conditions is related to the mechanism of primary angle closure. It is important to analyze both the angle structure and peripheral IT in each quadrant.
authors.affiliation: Department of Ophthalmology, Kobe City Medical Center General Hospital, 2-1-1, Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan, hirose@kcho.jp.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Hirose
authors.forename: Masayuki
authors.initials: M
authors.lastname: Hata
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Ito
authors.forename: Takaaki
authors.initials: T
authors.lastname: Matsuki
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kurimoto
mesh_terms: D000368:Aged; D000867:Anterior Chamber / Q000503:physiopathology*; D003623:Dark Adaptation; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis / Q000503:physiopathology*; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D007498:Iris / Q000473:pathology / Q000528:radiation effects*; D008027:Light; D008297:Male; D041623:Tomography, Optical Coherence