Purchase this article with an account.
Y. Barkana, N. Harizman, J.M. Liebmann, R. Ritch; Measurements of Optic Disc Size With HRT II, OCT3 and Funduscopy Are Not Interchangeable . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4347.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To assess the interchangeability of optic disc size measurements using slit–lamp funduscopy, OCT3 and HRT–II in clinical practice.
Measurements of vertical disc diameter (VDD) following pupillary dilation were obtained with the three methods. A single investigator, masked to the imaging results, measured VDD at the slit–lamp using a 78D lens to project a narrow beam within the scleral ring and read its size on the scale of the slit–lamp. Another masked investigator measured VDD using the interactive measurements option of the HRT. VDD was directly read from OCT printouts. True agreement between methods in measuring VDD was assessed using Bland–Altman graphs and 95% limits of agreement (LoA). Disc area was obtained from OCT and HRT printouts. Discs were classified as small, average or large; for this purpose we defined average size according to diameter or area as 1) mean±SD or 2) middle tertile. Agreement in classification of discs as small, average or large was assessed using kappa statistics.
48 patients (24 females, 24 males) were enrolled (mean age 53.4±14.3). VDD (mean±SD) was 1.58±0.15, 1.70±0.22, and 1.90±0.24 mm with funduscopy, HRT and OCT, respectively. Very large LoA were observed: –0.29 to +0.70 mm for OCT and HRT, –0.07 to 0.71 mm for OCT and funduscopy, and –0.29 to 0.53 mm for HRT and funduscopy. There was poor agreement (kappa<0.4) in classification of disc size as small, average or large whether disc diameter or area was compared and using either definition of disc size.
Despite good reported reliability of individual methods, we observed a large range of differences in estimating disc size with HRT, OCT and funduscopy. This precludes interchangeable use of these measurements in clinical practice, and does not allow simple conversion formulas to be proposed. In addition, there is poor agreement between these methods in classifying disc size as small, average, or large. At present, estimation of both absolute and relative disc size can only be defined separately for each measurement modality.
This PDF is available to Subscribers Only