Comparison between subjective and objective cup-to-disc (C/D) ratio assessment in ocular hypertension

James D Brandt, C. A. Johnson, S. Demirel

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Purpose. Optic nerve head assessment was performed as part of an on-going, longitudinal study of structure/function relationships in ocular hypertension and early glaucoma. The data reported here was gathered to allow comparisons between different methods of nerve head assessment and to evaluate the usefulness of these modalities for diagnosis of glaucoma. Methods. 136 ocular hypertensives (271 eyes) had their C/D ratios estimated using the Heidelberg Retina Tomograph (HRT), the Glaucoma-Scope (GS) and clinical assessment by an experienced observer (JDB) of stereo nerve head photographic pairs taken with the Nidek 3DX stereo disc camera (3DX). Comparisons were made among the three techniques. A subgroup (19) of the 3DX assessments were performed twice to allow calculation of test-retest correspondence for this method. Results. Best correlation was found between test-retest for 3DX assessment (r2=0.9), followed by 3DX and GS (r2=0.67), 3DX and HRT (r2=0.51) and finally between HRT and GS (r2=0.50). Using discrepancy analysis (Bland & Altman, 1986) it was found that the 95% confidence limits for prediction of C/D values on one imaging device based on the estimates obtained on the other imaging device was ±0.3. The 95% confidence interval for retest estimates with the 3DX measure was ±0.15. Conclusions. Although there was moderate to good agreement among the three methods, the absolute values of C/D estimates were quite different. Imaging techniques use different physical principles in generating their estimates of C/D ratio. Therefore, some of the lack of agreement may be related to differences in defining a reference plane, and consequently the boundaries of the optic disc. Ultimately, however, the usefulness of imaging techniques for early detection of glaucoma and monitoring of progression may not be reflected in their agreement with each other or with clinical methods, but in their ability to detect small amounts of change over time. Longitudinal data is being gathered to allow this to be examined.

Original languageEnglish (US)
JournalInvestigative Ophthalmology and Visual Science
Issue number3
StatePublished - Feb 15 1996

ASJC Scopus subject areas

  • Ophthalmology


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