rss
Br J Ophthalmol 1998;82:1118-1124 doi:10.1136/bjo.82.10.1118
  • Original Article
    • Clinical science

Vertical cup/disc ratio in relation to optic disc size: its value in the assessment of the glaucoma suspect

  1. David F Garway-Heath,
  2. Simon T Ruben,
  3. Ananth Viswanathan,
  4. Roger A Hitchings
  1. Glaucoma Unit, Moorfields Eye Hospital, City Road, London EC1V 2PD
  1. Mr D F Garway-Heath.
  • Accepted 24 March 1998

Abstract

AIMS The vertical cup/disc ratio (CDR) has long been used in the assessment of the glaucoma suspect, though the wide range of CDR values in the normal population limits its use. Cup size is related physiologically to disc size and pathologically to glaucomatous damage. Disc size can be measured at the slit lamp as the vertical disc diameter (DD). The ability of the CDR, in relation to DD, to identify glaucomatous optic discs was investigated.

METHODS 88 normal, 53 early glaucoma, and 59 ocular hypertensive subjects underwent stereoscopic optic disc photography and clinical biometry. Photographs were analysed in a masked fashion by computer assisted planimetry. The relation between vertical cup diameter and DD was explored by linear regression, and expressed in terms of CDR. The upper limit of normal was defined by the 95% prediction intervals of this regression (method 1) and by the upper 97.5 percentile for CDR (method 2). The sensitivity and specificity of CDR to identify an optic disc as glaucomatous was tested with these disc size dependent and disc size independent cut offs in small, medium, and large discs.

RESULTS The CDR was related to DD by the equation CDR = (−1.31 + (1.194 × DD))/DD. The sensitivity in small, medium, and large discs was 80%, 60%, and 38% respectively for method 1 and 33%, 67%, and 63% respectively for method 2. Specificity was 98.9% (method 1) and 97.7% (method 2).

CONCLUSIONS The CDR, relative to disc size, is useful clinically, especially to assist in identifying small glaucomatous discs.

Footnotes

    This Article

    1. Abstract
    2. Full text
    3. PDF

    Responses

    1. Submit a response
    2. No responses published

    Register for free content

    The full back archive is now available for all BMJ Journals. Institutional subscribers may access the entire archive as part of their subscription. Personal subscribers will also have access to all content when logged in. Non-subscribers who register have free access to all articles published before 2006 right back to volume 1 issue 1. Register here to access the free archive of all BMJ Journals.

    Don't forget to sign up for content alerts so you keep up to date with all the articles as they are published.