Quality and Reproducibility of Retinal Thickness Measurements in Two Spectral-Domain Optical Coherence Tomography Machines

Abstract

To evaluate the accuracy and reproducibility of retinal thickness measurements in exudative age-related macular degeneration (AMD) by the Spectralis (Heidelberg Engineering, Heidelberg, Germany) and the Cirrus (Carl Zeiss Meditec, Dublin, CA) optical coherence tomography (OCT) systems. Eyes with exudative age-related macular degeneration were randomly assigned to one of eight groups, each different in the sequence of examiner and OCT system. The 512 × 128 cube program of the Cirrus and the 30° × 25° volume scan containing 32 lines of the Spectralis were performed twice. The correlation between the examinations was expressed by the interclass correlation coefficient (ICC). Enrolled in the study were 112 patients and 112 eyes (mean age, 76.5 ± 7.9 years; range 51-89), with 14 patients in each group. The mean error scores per line were 0.53 and 0.52 in the Cirrus, significantly (P < 0.001) lower than in the Spectralis (0.83 and 0.98). For automatic central retinal thickness (CRT), the ICC for Cirrus (all examinations calculated) was 0.61 for groups 1 to 4 (the same examiner) and 0.65 for groups 5 to 8 (two different examiners); for Spectralis (13.4% not calculated) the ICC was 0.93 for groups 1 to 4 and 0.86 for groups 5 to 8. After error correction, the Cirrus ICC improved to 1.0 and 0.99 and the Spectralis ICC to 1.0 in both groups. Considerable differences were found between the two systems, both of which incorporate the spectral-domain technology. Different positioning of segmentation lines, control of localization, density of included scan lines, and number of available maps explain the differences in segmentation quality and reproducibility. Manual correction of segmentation and centralization improves the reproducibility.