Article Text

Download PDFPDF
The effect of optic disc diameter on vertical cup to disc ratio percentiles in a population based cohort: the Blue Mountains Eye Study
  1. J G Crowston,
  2. C R Hopley,
  3. P R Healey,
  4. A Lee,
  5. P Mitchell
  1. Centre for Vision Research, Department of Ophthalmology, Westmead Millennium and Save Sight Institutes, University of Sydney, Australia
  1. Correspondence to: Dr P Mitchell Centre for Vision Research, Department of Ophthalmology, University of Sydney, Hawkesbury Rd, Westmead, NSW, Australia, 2145; paul_mitchellwmi.usyd.edu.au

Abstract

Objective: The 97.5th percentile for vertical cup to disc ratio (VCDR) has been proposed as a useful tool to assist in the diagnosis of glaucoma in population studies. Previous reports of VCDR percentiles have either not been adjusted for disc size or have been calculated by regression analysis from small hospital based cohorts. The authors’ aim was to generate VCDR percentiles in a large, population based sample.

Methods: Data were collected from 3654 individuals, aged 49 years or older, living in the Blue Mountains, west of Sydney. Vertical disc diameter and VCDR were determined by planimetry from stereo optic disc photographs. The distribution of VCDR and percentiles (95th, 97.5th, 99th) were calculated.

Results: 6678 eyes were included in the analysis. Median cup to disc ratio, 95th, 97.5th, and 99th percentile increased with vertical optic disc diameter in a linear fashion. An increase of 0.2 in median VCDR (0.35 to 0.55) was observed between small (1.1–1.3 mm) and large (1.8–2.0 mm) optic discs. An equivalent increase of 0.2 (0.59 to 0.74) was observed for the 97.5th percentile from small to large discs.

Conclusion: VCDR percentiles for a “normal” population, adjusted for vertical optic disc diameter are presented. One quarter of all discs fell within the small or large disc categories highlighting the importance for estimating optic disc size. These data may assist in the diagnosis of glaucoma in clinical practice as well as providing a normative database. Sole use of VCDR percentile cut offs in defining glaucoma cases in population surveys requires further validation.

  • cup to disc ratio
  • percentiles
  • glaucoma
  • optic nerve
  • Blue Mountains Eye Study
  • VCDR, vertical cup to disc ratio
  • VDD, vertical disc diameter
  • cup to disc ratio
  • percentiles
  • glaucoma
  • optic nerve
  • Blue Mountains Eye Study
  • VCDR, vertical cup to disc ratio
  • VDD, vertical disc diameter

Statistics from Altmetric.com

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Footnotes

  • Supported by the Australian National Health & Medical Research Council, Canberra Australia (Grant No 974159) and the Keeler Scholarship, Royal College of Ophthalmologists, London, UK