Reproducibility of RTVue Retinal Nerve Fiber Layer (RNFL) Thickness and Optic Disc Measurements and Agreement With Stratus OCT Measurements

Abstract

Purpose: : To evaluate the reproducibility of a novel Spectral Domain OCT, the RTVue (Optovue Inc, Fremont, CA) by assessing the repeatability of consecutive RNFL and optic disc measurements and to estimate the agreement between RTVue and Stratus OCT measurements.

Methods: : 54 eyes of 29 normal subjects (mean age 62.96, S.D.= 9.98 years; 19 females) from the Diagnostic Innovations in Glaucoma Study (DIGS) were evaluated. Subjects were examined using the RTVue (three consecutive scans) followed by the Stratus OCT, within a one hour period. The within subjects standard deviation (Sw), the coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were calculated to assess the reproducibility of each RTVue RNFL and optic disc parameter measurement. Pearson’s r correlation coefficients were calculated and Bland-Altman plots with 95% limits of agreement were constructed to estimate the agreement with the Stratus OCT measurement.

Results: : For RNFL measurements, reproducibility of global measurements was better than reproducibility of sectoral measurements: RTVue RNFL thickness CVs ranged from 2.1% for Average RNFL Thickness to 10.5% for Inferior Temporal RNFL Thickness while the ICCs were 0.97 and 0.77, respectively. For optic disc parameters, CVs ranged from 0.3% for Disc Area to 21.2% for Cup Volume while ICCs were 1.00 and 0.98, respectively. Moderate to strong correlations were found between RTVue and Stratus OCT measurements for both RNFL (Pearson’s r ranging from 0.43 for Temporal RNFL Thickness to 0.89 for Superior RNFL Thickness) and optic disc parameters (Pearson’s r ranging from 0.57 for Rim Area to 0.93 for Cup Area). The 95% limits of agreement between RTVue and Stratus OCT ranged from -5.2 to 21.9 µm for Average RNFL Thickness to -21.6 to 42.9 µm for Temporal RNFL Thickness while they ranged from -0.1 to 0.2 for C/D Area Ratio and -0.9 to 0.1 mm² for Disc Area.

Conclusions: : RTVue optic disc and RNFL measurements are highly reproducible in normal subjects with the lowest CVs measured for global RNFL parameters and Disc Area. In general, all RTVue measurements correlated well with Stratus OCT measurements while agreement with the Stratus OCT varied among the parameters measured. Further studies are needed to evaluate the reproducibility of RTVue measurements in glaucomatous patients.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)