title: Gonioscopy in adult Chinese: the Liwan Eye Study.
abstract: OBJECTIVE
  To assess gonioscopic characteristics of the drainage angle in adult Chinese in an urban area of southern China.
  
  
  METHODS
  Clustered random sampling was used to select adults aged 50 years and older in Liwan District, Guangzhou. Gonioscopy was performed on all the subjects. The geometric angle width was graded in the superior and inferior quadrants, according to the Spaeth system. In addition, apparent and true iris insertion was classified in four quadrants with static and dynamic gonioscopy. The peripheral iris profile was described as steep, regular, concave, and plateau. Data are presented for all phakic right eyes. Secondary or iatrogenic cases were excluded in the analysis of peripheral anterior synechiae (PAS).
  
  
  RESULTS
  Among 1405 participants in the study, data from 1330 (95%) right eyes were available for analysis. Iridotrabecular angles (ITA) < or =20 degrees were present in 36.9% (95% CI: 34.3%-40.0%) of eyes superiorly and in 27.9% (95% CI: 25.5%-30.4%) inferiorly. Narrower ITAs were more common in the older people (sex-adjusted odds ratio [OR] = 1.1 per year of life; P < 0.001) and the women (age-adjusted OR = 2.5, P < 0.001). Apparent iris insertion of grade A or B (with pigmented trabecular meshwork not visible) by quadrant was observed in 27.2% superiorly, 12.0% nasally, 7.7% inferiorly, and 14.2% temporally. Narrow angles (in which pigmented trabecular meshwork was not visible in three or more quadrants) were identified in 11.0% (95% CI: 9.3%-12.7%) of right eyes. Overall, 33.3% of eyes had a steep iris profile, 54.2% were normal, 2.7% were concave, and 10.1% were graded plateau. PAS were seen in 30 of 146 (20.5%) eyes with narrow angles and in 7 (0.6%) of 1184 eyes with angles that did not meet criteria for narrow angles. PAS were more likely with narrower angles, with 0%, 0.3%, and 1.9% of eyes with a mean ITA of 40 degrees, 30 degrees, and 20 degrees, respectively, having PAS as opposed to 12.6% and 27.5% for those with ITA 10 degrees and 0 degrees , respectively.
  
  
  CONCLUSIONS
  Ten percent of this population of southern Chinese persons 50 years of age and older had narrow angles. PAS were present in one fifth of these people. From these cross-sectional data, it is unclear which of these individuals are at highest risk of the development of primary angle-closure (PAC) glaucoma. Longitudinal studies are necessary to determine appropriate strategies for preventing this potentially blinding outcome.
authors.affiliation: Institute of Ophthalmology, University College London (UCL), London, United Kingdom.
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Foster
authors.forename: Jian
authors.initials: J
authors.lastname: Ge
authors.forename: Wenyong
authors.initials: W
authors.lastname: Huang
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: Peng T
authors.initials: PT
authors.lastname: Khaw
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis* / Q000453:epidemiology*; D006068:Gonioscopy; D006801:Humans; D007498:Iris / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D014129:Trabecular Meshwork / Q000473:pathology*