Comparing retinal thickness measurements from cirrus spectral domain- and stratus time domain-optical coherence tomography

Purpose: The purpose of this study was to compare retinal measurements obtained using spectral domain-optical coherence tomography with measurements obtained using time domain-optical coherence tomography. Methods: Three hundred and seventy subjects were recruited at three university-based and one community-based retina practice for a cross-sectional observational study. For each subject, one eye was enrolled as the study eye. A Stratus Fast Macular scan was performed, and a Cirrus 200 × 200 Macular Cube scan was performed. Both instruments segment the acquired images to generate retinal thickness values and report averages measured in nine subfields defined by the Early Treatment Diabetic Retinopathy Study. These average values were compared with each other quantitatively using linear regression and Bland-Altman plots. Results: Of the recruited subjects, 283 had acceptable images taken on the same day with both the Cirrus and Stratus devices. Mean differences between the instruments were noted in all subfields for all disease categories and ranged from 29 μm (outer superior subfield) to 54 μm (central subfield). Conclusion: Differences between time domain and spectral domain measurements of retinal thickness depend on pathology and location. Comparisons across instruments should be made with caution.