Reproducibility of retinal thickness measurements on normal and pathologic eyes by different optical coherence tomography instruments.

PURPOSE

To compare retinal thickness measurements produced by different time-domain and spectral-domain optical coherence tomography (TD-OCT and SD-OCT) devices when imaging normal and pathologic eyes.

DESIGN

Prospective, observational study in an academic institutional setting.

METHODS

A total of 110 eyes were imaged by 6 different OCT devices: Stratus and Cirrus (Carl Zeiss Meditec Inc), Spectralis HRA+OCT (Heidelberg Engineering), RTVue-100 (Optovue Inc), SDOCT Copernicus HR (Optopol Technology S.A.), and 3D OCT-1000 (Topcon Corporation). Eyes were normal or affected by different pathologies of the retina, including exudative and nonexudative age-related macular degeneration, epiretinal membrane, cystoid macular edema, and macular hole. For each instrument we used standard analysis protocols for macular thickness evaluation. Mean retinal thickness values between the instruments in the ETDRS central circular 1000-μm-diameter areas and in the ETDRS midperipheral circular 3000-μm-diameter areas were compared.

RESULTS

The 6 different devices produced measurements that differ in variance (Bartlett test, P = .006), and mean values (Friedman test, P < .001). Bland-Altman analysis revealed that the limits of agreement for all the comparisons were not acceptable. Regression was calculated and it was elaborated into a conversion table, despite a high standard error for both intercepts and slope conversion values.

CONCLUSIONS

This study suggests that retinal thickness measurements obtained with various OCT devices are different beyond clinical practice tolerance, according to Bland-Altman analysis. Furthermore, regression analysis reveals high standard error values. These differences appear to be primarily attributable to the analysis algorithms used to set retinal inner and outer boundaries.