Comparing central retinal thickness in diabetic macular edema measured by two different spectral-domain optical coherence tomography devices

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. CRT was measured in 63 eyes of 32 patients with DME using both instruments on the same day. CRT measurements were significantly greater for the Spectralis than the Cirrus (p < 0.0003, n = 63, paired t test); mean CRT values were 382 +/- A 136 mu m with the Cirrus and 394 +/- A 139 mu m with the Spectralis. In eyes with poor best-corrected visual acuity (BCVA) (< 20/40), mean CRT was 378 +/- A 130 mu m with the Cirrus and 395 +/- A 139 mu m 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 +/- A 142 mu m with the Cirrus and 393 +/- A 140 mu m with the Spectralis (p < 0.005, n = 34). Foveal retinal thickness measurements may vary among SD-OCT devices. The differences between instruments could affect the results of a multicenter study.