Retinal Nerve Fiber Layer Thickness Measurement by Fourier-domain Optical Coherence Tomography: A Comparison Between Cirrus-HD OCT and RTVue in Healthy Eyes

Abstract

To compare retinal nerve fiber layer (RNFL) thickness measurements by 2 Fourier-domain optical coherence tomography (OCT) instruments: Cirrus-HD OCT and RTVue. Twenty-three eyes of 23 healthy participants underwent RNFL thickness measurement using both devices on the same day. The NMH4 and Optic Disk Cube 200x200 protocols were used, respectively, for scan acquisition with RTVue and Cirrus-HD OCT. Measurements were compared by means of a paired t test. RTVue gave higher mean RNFL thickness values than Cirrus-HD OCT in the superior (128.44+/-22.48 vs. 119.73+/-18.22 mu, P=0.0002), inferior (137.15+/-21.99 vs. 124.94+/-22.51 mu, P<0.0001), nasal (77.58+/-15.61 vs. 70.21+/-11.53 mu, P=0.0009), and temporal (78.09+/-10.05 vs. 67.08+/-9.60 mu, P<0.0001) quadrants, as well as a higher 360 degrees average measurement (105.88+/-14.59 vs. 95.21+/-12.45 mu, P<0.0001). The average difference between the 2 instruments showed a standard deviation too high to calculate a reliable correcting factor for comparing a pair of individual scans taken with the 2 instruments (superior quadrant 8.70+/-9.19 mu; inferior quadrant 13.11+/-5.4 mu; nasal quadrant 7.37+/-9.18 mu; temporal quadrant 11.01+/-8.50 mu; average measurement: 10.67+/-4.88 mu). In healthy eyes RNFL measurements taken with RTVue and Cirrus-HD OCT show significant differences that make the measurements themselves noninterchangeable.