title: Can intraocular pressure asymmetry indicate undiagnosed primary glaucoma? The Chennai Glaucoma Study.
abstract: OBJECTIVE
  : To investigate the association of intraocular pressure (IOP) asymmetry with undiagnosed primary glaucoma in rural and urban populations of south India.
  
  
  METHODS
  Chennai Glaucoma Study is a population-based cross-sectional study. The participants were adults, 40 years or older. The prevalence of primary glaucoma was defined using International Society of Geographical and Epidemiological Ophthalmology classification. IOP asymmetry was diagnosed when the difference in IOP between 2 eyes was >3 mm Hg. Analysis included only bilaterally phakic subjects. We excluded subjects with known glaucoma, secondary glaucoma, pseudoexfoliation, ocular trauma, and ocular surgery.
  
  
  RESULTS
  Of 6310 subjects, 3052 (48.4%) were rural residents. The mean age was 52 (standard deviation: 9.5) years. The prevalence of IOP asymmetry increased steadily with increasing patient age. The prevalence of undiagnosed primary glaucoma was 3.4% (95% confidence interval, 2.9-3.8). Undiagnosed primary glaucoma was 3 times more common in subjects with IOP asymmetry than without (odds ratio 3.08, 95% confidence interval, 2.1-4.3). The specificity of IOP asymmetry in detecting undiagnosed primary glaucoma was 92%.
  
  
  CONCLUSIONS
  IOP asymmetry of >3 mm Hg has limited accuracy for the detection of undiagnosed primary glaucoma. The criterion should be combined with other indicators of glaucoma to build the pretest probability of the disease.
authors: Glaucoma Project, Vision Research Foundation, Sankara Nethralaya, Chennai, India.
authors: Nikhil S
authors: NS
authors: Choudhari
authors: Ronnie
authors: R
authors: George
authors: Mani
authors: M
authors: Baskaran
authors: Ramesh S
authors: RS
authors: Ve
authors: Prema
authors: P
authors: Raju
authors: L
authors: L
authors: Vijaya
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D063171:Corneal Pachymetry; D003430:Cross-Sectional Studies; D005189:False Positive Reactions; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D005902:Glaucoma, Open-Angle / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D006801:Humans; D007194:India / Q000453:epidemiology; D007429:Intraocular Pressure / Q000502:physiology*; D032801:Iridectomy; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D015203:Reproducibility of Results; D012424:Rural Population / Q000706:statistics & numerical data; D012680:Sensitivity and Specificity; D014065:Tonometry, Ocular; D014505:Urban Population / Q000706:statistics & numerical data