Abstract

SO.15.03

Measurement of the disc area by indirect ophthalmoscopy

Haustein M., Schmidt E., Spörl E., Pillunat L. E., Böhm A. G.
Department of Ophthalmology, University Dresden

Objective: In the diagnosis of glaucoma c/d-ratio plays an important role. To evaluate the clinical relevance of the c/d-ratio the size of disc needs to be considered. In this study we compared the disc size measured by Heidelberg retina tomograph (HRT) wiht measurements taken by indirect ophthalmoscopy (iO) using different ophthalmoscopic lenses.
Methods: The vertical and horizontal disc diameters were measured in 57 eyes of 29 subjects with a Haag Streit slit lamp by different VOLK lenses (60 D, 78 D-, 90 D and the Superfield-NC). By means of the following ellipse formula (horizontal papilla diameter x vertical papilla diameters x π/4) the disc area was calculated. The same eyes were measured by the HRT. The measurements obtained by iO were compared with the HRT measurements by Bland-Altman plots.
Results: Following deviations resulted between HRT- and iO-disc areas: 0.119±0.51 mm² (60 D VOLK lens), 0.224±0.57 mm² (78 D VOLK lens), 0.10±0.51 mm² (90 D VOLK lens) and -0.07±0.47 mm² (Superfield NC-VOLK lens). Only measurements performed with the 78 D lens showed statistically significant differences compared with the HRT values (t-test, P=0.004). The P-values for the 60 D, 90 D and Superfield amounted 0.083, 0.147 and 0.257, respectively.
Conclusions: The iO disc area measurements ontained by the 90 D VOLK lens showed the best agreement with the HRT measurments. With this lens the disc areas differ only about 0.1 mm² from the HRT examination. The 78 D lens showed the greatest deviation.

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