title: Planimetric optic disc parameters in normal eyes: a population-based study in South India.
abstract: OBJECTIVE
  To study the optic disc parameters of normal eyes in a population-based south Indian study.
  
  
  METHODS
  One hundred and fifty three subjects from a population-based sample of 1060 included in the Andhra Pradesh Eye Disease Survey (APEDS) were enrolled in the optic disc study. The male-female ratio, the refractive error and distribution of other ocular parameters in the disc study subjects and the APEDS were not significantly different. Magnification corrected morphometry of optic disc photographs obtained by Zeiss telocentric fundus camera was carried out in one randomly chosen eye of each of these 143 subjects.
  
  
  RESULTS
  The mean optic disc parameters with the 95% confidence intervals for the distribution were: disc area 3.37 mm2 (2.04 - 4.7), vertical disc diameter 2.12 mm (1.67 - 2.57), vertical cup to disc ratio 0.37 (0.19 -0.55) and neuroretinal rim area 2.8 mm2 (1.76 - 3.84). The disc area, the vertical cup to disc ratio and the rim area showed a normal distribution. The cup to disc ratio correlated with the vertical disc diameter but the association was not strong.
  
  
  CONCLUSIONS
  The disc area, the vertical cup to disc ratio and the neuroretinal rim area are normally distributed in the South Indian population. The normal optic disc parameters would form a basis for future comparisons in different forms of glaucoma.
authors.affiliation: VST Centre for Glaucoma Care, and Public Health Ophthalmology Service, L.V. Prasad Eye Institute, Hyderabad, India. gcs@lvpeye.stph.net.in
authors.forename: G C
authors.initials: GC
authors.lastname: Sekhar
authors.forename: K
authors.initials: K
authors.lastname: Prasad
authors.forename: R
authors.initials: R
authors.lastname: Dandona
authors.forename: R K
authors.initials: RK
authors.lastname: John
authors.forename: L
authors.initials: L
authors.lastname: Dandona
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D007194:India; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000033:anatomy & histology*; D011159:Population Surveillance; D012016:Reference Values; D017678:Sex Distribution