Improved Repeatability of Retinal Thickness Measurements Using Line-Scan Ophthalmoscope Image-Based Retinal Tracking

BACKGROUND AND OBJECTIVE: To assess repeatability and speed of a line-scan ophthalmoscope (LSO) image-based tracking system and compare to the point-scanning approach. PATIENTS AND METHODS: Thirty-five eyes with retinal diseases underwent volume scans using two spectral-domain optical coherence tomography (OCT) devices: a line-scan tracking Cirrus HD-OCT (Carl Zeiss Meditec; Dublin, CA) and point-scan tracking Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany). Eyes were also imaged on the Cirrus HD-OCT with tracking disabled. RESULTS: Mean difference in central subfield thickness (CST) between consecutive scans was 2.6 mu m for the Cirrus without tracking, 1.7 mu m with tracking, and 3.6 mu m for the Spectralis. The repeatability standard deviation was 3.0 mu m for the Cirrus without tracking, 1.5 mu m with tracking, and 4.0 mu m for the Spectralis. Coefficient of variation for the CST was 1.1% for the Cirrus without tracking, 0.5% with tracking, and 1.4% for the Spectralis. Mean scan acquisition time was 12.3 +/- 6.2 seconds for the Spectralis, 7.8 +/- 6.7 for the Cirrus with tracking, and 4.3 +/- 0.6 for the Cirrus without tracking. CONCLUSION: Real-time LSO image-based retinal tracking appears to improve repeatability of OCT retinal thickness measurements.