title: Dynamic analysis of dark-light changes of the anterior chamber angle with anterior segment OCT.
abstract: OBJECTIVE
  To describe the use of anterior segment optical coherence tomography (OCT) in studying the dynamic dark-light changes of the anterior chamber angle.
  
  
  METHODS
  Thirty-seven normal subjects with open angles on dark-room gonioscopy and 18 subjects with narrow angles were analyzed. The dynamic dark-light changes of the anterior-chamber angle were captured with real-time video recording. The angle opening distance (AOD500) and trabecular iris space area (TISA500) of the nasal angle and the pupil diameter in each of the representative serial images were measured. Linear regression analysis was performed to investigate the association between AOD500/TISA500 and pupil diameter. Demographic and biometry measurements associated with the AOD difference (AOD500((light)) - AOD500((dark))) and TISA difference (TISA500((light)) - TISA500((dark))) were analyzed with univariate and multivariate regression models.
  
  
  RESULTS
  The AOD500/TISA500 measured in the light in the open-angle and the narrow-angle groups were 694 +/- 330 microm/0.24 +/- 0.10 mm(2) and 265 +/- 78 microm/0.10 +/- 0.03 mm(2), respectively. These values were significantly greater than the AOD500/TISA500 measured in the dark (492 +/- 265 microm/0.16 +/- 0.08 mm(2) and 119 +/- 82 microm/0.05 +/- 0.04 mm(2), respectively, all with P < 0.001). The ranges of the AOD/TISA difference were 13 to 817 microm/0.011 to 0.154 mm(2), with an average of 180 microm/0.073 mm(2). Multivariate regression analysis identified a positive correlation between anterior chamber depth and the AOD/TISA difference. Fifty eyes showed significant correlations between AOD/TISA and pupil diameter, whereas one eye showed no association. Four eyes in the narrow angle group developed appositional angle closure in the dark.
  
  
  CONCLUSIONS
  The dynamic dark-light changes of the anterior chamber angle can be imaged and analyzed with anterior segment OCT. Although the angle width generally decreased linearly with increasing pupil diameter, the differences of the angle width measured in the dark and in the light varied substantially among individuals.
authors.affiliation: Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, Peoples Republic of China. tlims00@hotmail.com
authors.forename: Christopher Kai-shun
authors.initials: CK
authors.lastname: Leung
authors.forename: Carol Yim Lui
authors.initials: CY
authors.lastname: Cheung
authors.forename: Haitao
authors.initials: H
authors.lastname: Li
authors.forename: Syril
authors.initials: S
authors.lastname: Dorairaj
authors.forename: Cedric Ka Fai
authors.initials: CK
authors.lastname: Yiu
authors.forename: Amy Lee
authors.initials: AL
authors.lastname: Wong
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Liebmann
authors.forename: Robert
authors.initials: R
authors.lastname: Ritch
authors.forename: Robert
authors.initials: R
authors.lastname: Weinreb
authors.forename: Dennis Shun Chiu
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000368:Aged; D000867:Anterior Chamber / Q000378:metabolism* / Q000528:radiation effects; D003623:Dark Adaptation; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000378:metabolism*; D005902:Glaucoma, Open-Angle / Q000378:metabolism*; D006068:Gonioscopy; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D011680:Pupil / Q000502:physiology / Q000528:radiation effects; D012044:Regression Analysis; D041623:Tomography, Optical Coherence / Q000379:methods*