Inter-device Variability of the Stratus Optical Coherence Tomography

Purpose: To assess inter-device measurement variability with the Stratus optical coherence tomography (OCT). Design: Evaluation of diagnostic test technology. Methods: Eight eyes of eight healthy subjects were examined with four different Stratus machines in four medical centers during a period of five hours using fast retinal nerve fiber layer (RNFL) and fast macula protocols. Inter-device measurement variability and signal strength was assessed with standard deviation, coefficient of variance, and intraclass correlation coefficient (ICC). Spearman correlation coefficient was calculated between signal strength and thickness measurements. Results: Statistically significant differences were not found for all macular parameters and all but one RNFL parameter. Mean signal strengths obtained with the four Stratus machines were significantly different; the newer the machine, the stronger signal strength it produced. Some RNFL parameters were moderately and statistically significantly correlated with signal strength. Conclusions: We did not observe statistically significant differences in any macular and all but one RNFL parameter between the four Stratus OCT machines. Signal strength was significantly different between the machines, and significantly correlated with some RNFL parameters. Inter-machine variability in RNFL measurements may have clinical significance. Signal strength should be included in the assessment of measurements obtained on different machines and in serial examinations with a single Stratus machine during patient follow-up.