The effect of axial length on the variability of Stratus optical coherence tomography

To evaluate the effect of axial length on the variability of retinal nerve fiber layer (RNFL) thickness measurements using the Stratus optical coherence tomography (OCT) in normal and glaucomatous eyes.

We measured the RNFL thickness in 474 subjects using the Stratus OCT twice during the same day. Axial length was measured with the IOLMaster, and refractive error was the absolute value of the spherical equivalent measured with an auto ref-keratometer. Standard deviation in overall mean RNFL thickness was used as the dependent variable to identify significant correlations.

Long axial length affected the variability in the RNFL thickness value by stratus OCT at the temporal quadrant (p = 0.006) and clock-hour sector 9 (p = 0.001). Refractive error also affected the variability of the RNFL thickness value by stratus OCT at the temporal quadrant (p = 0.025) and clock-hour sector 9 (p = 0.024).

It is clinically significant that longer axial length demonstrates greater variability in temporal area as detected by OCT, a measurement which correlates with the preferably damaged position in the myopic glaucoma eye.