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