Aligning scan locations from consecutive spectral-domain optical coherence tomography examinations : a comparison among different strategies

PURPOSE: We compared intrasession repeatability values produced by different spectral-domain optical coherence tomography (SD-OCT) instruments when measuring macular retinal thickness from consecutive examinations. METHODS: A total of 40 eyes from 23 healthy subjects and 47 eyes from 42 patients with macular edema were enrolled in the study. Subjects underwent two consecutive SD-OCT examinations using three instruments: spectralis HRA+OCT, Cirrus, and RS 3000. For the second SD-OCT examination, the scan location was aligned to the baseline exam using different strategies: RS 3000 eye-tracking (pre-acquisition), Spectralis follow-up (during acquisition), Cirrus fovea finding (postacquisition), and Cirrus macular change analysis (postacquisition). Macular retinal thickness values from the consecutive examinations were evaluated to assess repeatability of the measurements. RESULTS: In healthy subjects all of the strategies used for scan location alignment for the second examination provided good repeatability. For instance, intraclass correlation coefficients (ICC) from the central subfield were between 0.88 (RS 3000 eye-tracking) and 0.99 (Spectralis follow-up). In subjects affected by macular edema, the results were excellent. Cirrus macular change analysis and Spectralis follow-up produced ICC values equaled 1.00 in the central subfield. Cirrus fovea finding and RS 3000 eye-tracking produced slightly lower ICC values (0.98 and 0.99, respectively) in the central subfield. CONCLUSIONS: All of the strategies for aligning consecutive SD-OCT scan locations produced repeatable retinal thickness values. The best results were obtained using the Spectralis with follow-up and Cirrus with macular change analysis.