Purpose: We evaluated central retinal thickness (CRT) in diabetic macular edema (DME) using two different spectral-domain (SD) optical coherence tomography (OCT) instruments: the Cirrus and Spectralis OCTs.
Methods: CRT was measured in 63 eyes of 32 patients with DME using both instruments on the same day.
Results: CRT measurements were significantly greater for the Spectralis than the Cirrus (p < 0.0003, n = 63, paired t test); mean CRT values were 382 ± 136 μm with the Cirrus and 394 ± 139 μm with the Spectralis. In eyes with poor best-corrected visual acuity (BCVA) (<20/40), mean CRT was 378 ± 130 μm with the Cirrus and 395 ± 139 μm with the Spectralis (p < 0.007, n = 29). In eyes with good acuity (equal to or better than 20/40), the mean CRT was 385 ± 142 μm with the Cirrus and 393 ± 140 μm with the Spectralis (p < 0.005, n = 34).
Conclusions: Foveal retinal thickness measurements may vary among SD-OCT devices. The differences between instruments could affect the results of a multicenter study.