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J. Kim, H. Ishikawa, M. L. Gabriele, G. Wollstein, R. A. Bilonick, L. Kagemann, J. S. Schuman; Novel Method to Establish Retinal Nerve Fiber Layer (RNFL) Thickness Measurement Comparability Between Time Domain Optical Coherence Tomography (TD-OCT) and Spectral Domain OCT (SD-OCT). Invest. Ophthalmol. Vis. Sci. 2009;50(13):4789.
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TD-OCT has been commonly used in clinical practice, producing a large inventory of circular scan data. SD-OCT produces 3D data volumes. The purpose of this study was to create a robust technique that makes TD-OCT circular scans comparable with 3D SD-OCT volumes.
Eleven eyes of 11 healthy subjects were assessed. Nine circumpapillary TD-OCT Fast RNFL Scans (Stratus OCT, Carl Zeiss Meditec, Dublin, CA) each set with 1 center and 8 displaced circles in known distance/directions, and one SD-OCT scan (Cirrus HD-OCT, Carl Zeiss Meditec, Dublin, CA; Optic Disc Cube 200x200) were obtained. The location of the TD-OCT circle scan was automatically detected within the SD-OCT volume scan using a software program of our own design. Mixed effect models were used to estimate the spatial deviation of the detected scan location on the SD-OCT 3D volume from the actual TD-OCT scan location to assess algorithm performance. Global and sectoral RNFL thickness measurements with or without scan location matching were also compared.
The difference [95% confidence interval] in scan circle center location between TD- and SD-OCT was 2.34 [1.24-3.44] pixels (70.20 [37.20-103.20] µm on the retina). There were significant differences in RNFL thickness measurements when SD-OCT/TD-OCT scan locations were not matched and no significant differences when they were matched, except for the superior quadrant and the 9, 12, and 6 o’clock sectors.
Our novel method of location matching bridges the gap between line and volume scan data, providing follow-up comparability between TD- and SD-OCT RNFL measurements.
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