title: Determinants and two-year change in anterior chamber angle width in a Chinese population.
abstract: OBJECTIVE
  To study the population distribution and longitudinal changes in anterior chamber angle width and its determinants among Chinese adults.
  
  
  METHODS
  Prospective cohort, population-based study.
  
  
  METHODS
  Persons aged 35 years or more residing in Guangzhou, China, who had not previously undergone incisional or laser eye surgery.
  
  
  METHODS
  In December 2008 and December 2010, all subjects underwent automated keratometry, and a random 50% sample had anterior segment optical coherence tomography with measurement of angle-opening distance at 500 μm (AOD500), angle recess area (ARA), iris thickness at 750 μm (IT750), iris curvature, pupil diameter, corneal thickness, anterior chamber width (ACW), lens vault (LV), and lens thickness (LT) and measurement of axial length (AL) and anterior chamber depth (ACD) by partial coherence laser interferometry.
  
  
  METHODS
  Baseline and 2-year change in AOD500 and ARA in the right eye.
  
  
  RESULTS
  A total of 745 subjects were present for full biometric testing in both 2008 and 2010 (mean age at baseline, 52.2 years; standard deviation [SD], 11.5 years; 53.7% were female). Test completion rates in 2010 varied from 77.3% (AOD500: 576/745) to 100% (AL). Mean AOD500 decreased from 0.25 mm (SD, 0.13 mm) in 2008 to 0.21 mm (SD, 13 mm) in 2010 (difference, -0.04; 95% confidence interval [CI], -0.05 to -0.03). The ARA decreased from 21.5 ± 3.73 10(-2) mm(2) to 21.0 ± 3.64 10(-2) mm(2) (difference, -0.46; 95% CI, -0.52 to -0.41). The decrease in both was most pronounced among younger subjects and those with baseline AOD500 in the widest quartile at baseline. The following baseline variables were significantly associated with a greater 2-year decrease in both AOD500 and ARA: deeper ACD, steeper iris curvature, smaller LV, greater ARA, and greater AOD500. By using simple regression models, we could explain 52% to 58% and 93% of variation in baseline AOD500 and ARA, respectively, but only 27% and 16% of variation in 2-year change in AOD500 and ARA, respectively.
  
  
  CONCLUSIONS
  Younger persons and those with the least crowded anterior chambers at baseline have the largest 2-year decreases in AOD500 and ARA. The ability to predict change in angle width based on demographic and biometric factors is relatively poor, which may have implications for screening.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Nathan G
authors.initials: NG
authors.lastname: Congdon
authors.forename: Xiangbin
authors.initials: X
authors.lastname: Kong
authors.forename: Mirjam E
authors.initials: ME
authors.lastname: Meltzer
authors.forename: Qianyun
authors.initials: Q
authors.lastname: Chen
authors.forename: Yangfa
authors.initials: Y
authors.lastname: Zeng
authors.forename: Yuanzhou
authors.initials: Y
authors.lastname: Huang
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000867:Anterior Chamber / Q000473:pathology*; D044466:Asian People / Q000208:ethnology; D058452:Axial Length, Eye / Q000473:pathology; D001699:Biometry; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D003315:Cornea / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis* / Q000208:ethnology; D006801:Humans; D007368:Interferometry; D007498:Iris / Q000473:pathology; D007908:Lens, Crystalline / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D011446:Prospective Studies; D011680:Pupil / Q000502:physiology; D012307:Risk Factors; D013997:Time Factors; D041623:Tomography, Optical Coherence