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C. Y. Mardin, F. K. Horn, D. Baleanu, A. G. M. Juenemann, R. Laemmer, F. Kruse, R. P. Tornow; Influence of Retinal Blood Vessels on Diagnostic Accuracy of Rnfl Thickness Measurements Using Spectral-Domain Oct to Detect Glaucoma. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3333.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the potential influence of retinal blood vessels (rbv) on the diagnostic accuracy of RNFL thickness measurements to detect glaucoma.
Circular B-Scans (diameter 3.4 mm, 768 AScans) around the optic nerve head (ONH) where acquired in 99 healthy subjects and 48 Glaucoma patients using spectral domain OCT (Spectralis HRA & OCT, Heidelberg Engineering) and RNFL thickness was measured. B-Scan images were exported and the position of rbv was calculated by locating the rbvs’ shadows in the layer of the pigment epithelium using a customized software (see fig.). RNFL thickness was set to zero at positions were rbv were found. Two data sets were used for further calculations: one with rbv included in the RNFL thickness results and one without rbv. The thickness values were averaged to 6 sectors (with 0° corresponding temporal, horizontal): temporal (315 - 34 deg), temporal-superior TS (34 - 79 deg), superior S (79 - 124 deg), nasal N (124 - 225 deg), inferior I (225 - 270 deg), temporal-inferior TI (270 - 315 deg). Diagnostic accuracy was investigated using ROC-curves for mean and sectoral RNFL thickness.
Mean thickness in normal subjects was (mean±SD) (99±9) µm and (88±8) µm with and without vessels, respectively. This resulted in a mean thickness of the rbv layer of 11 µm corresponding to 11 % of the total RNFL. The fraction of the rbv contribution to RNFL thickness in the 6 sectors was highest superiorly and temporally: T: (2±3) %, TS: (15±7) %, S: (15±9) %, N: (9±4) %, I: (14±7) %, TI: (15±6) %. There was no difference in the area under the ROC curves for mean RNFL thickness (0.982 vs 0.983) with and without rbv and in the 6 sectors.
The exclusion of rbv from RNFL thickness measurements using spectral domain OCT does not affect the diagnostic accuracy of RNFL thickness measurements in this data set.
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