Comparison of Macular Thickness Measurements Using Swept-Source and Spectral-Domain Optical Coherence Tomography in Healthy and Diabetic Subjects

Purpose To compare macular thicknesses measured using swept-source optical coherence tomography (SS-OCT) and spectral domain OCT (SD-OCT) in normal subjects, diabetics with diabetic retinopathy (DR) and diabetics without DR (NDR). Methods We analysed 510 normal eyes, 741 NDR eyes and 209 DR eyes. Mean macular thicknesses in Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, central point thicknesses (CPT), and macular volume were measured by SS-OCT and SD-OCT. We assessed agreement between SS-OCT and SD-OCT measurements by intraclass correlation coefficients (ICC) and Bland-Altman plots, and established a conversion equation relating central subfield (CSF), CPT and macular volume between the two devices. Results Macular thickness measurements by SS-OCT were significantly thinner than those by SD-OCT. The mean CSF thickness in normal eyes measured by SD-OCT and SS-OCT were 226.6 ± 19.1 μm (male 236.1 ± 19.1 μm vs female 223.0 ± 17.9 μm, p < 0.0001) and 258.4 ± 19.8 μm. In all three groups, the agreement between SS-OCT and SD-OCT was excellent (all ICC ≥ 0.866). For CSF the conversion equation SD-OCT = 31.95 + 0.999 × SS-OCT was derived. Using the equation, with 99.6% and 97.6% of the predicted values for CSF fell within 10% of the actual measurements in DR and NDR eyes, respectively. Conclusion We propose SS-OCT CSF thicknesses of 275 μm for males and 260 μm for females as the minimum criteria for macular edema in Chinese eyes. And SS-OCT measurements were significantly thinner than those of SD-OCT, we derived an equation to convert SS-OCT measurements to SD-OCT equivalents.