Comparison of Peripapillary Retinal Nerve Fiber Layer Thickness Measured by Two Different Optical Coherence Tomography Devices

To determine agreement between peripapillary retinal nerve fiber layer (RNFL) thickness measurements by two different spectral domain optical coherence tomography (SD-OCT) machines. Both eyes of 89 subjects were evaluated using Cirrus OCT (Carl Zeiss Meditec, Inc. Dublin, CA, USA) and Topcon OCT (3D OCT 1000, Topcon Corporation, Tokyo, Japan). One eye was randomly selected in each subject and peripapillary RNFL thickness measurements were compared. Bland Altman plots were used to assess the level of agreement. Forty-four healthy subjects (mean age, 47±15 years) and 45 patients with glaucoma (mean age, 55±14 years) were selected. Average peripapillary RNFL thickness measurements were significantly larger with Topcon OCT as compared to Cirrus OCT both in normal (101±12 vs 91±8 μm, P<0.001) and glaucomatous eyes (89±18 vs 76±16 μm, P<0.001). The limits of agreement (LOA) for average peripapillary RNFL thickness measurements were poor, -11 to 32 μm in normal and -4 to 30 μm in glaucomatous eyes. Peripapillary RNFL thickness values measured by Topcon OCT are greater than those measured by Cirrus OCT in both normal and glaucomatous eyes. Clinicians should be aware of this difference when monitoring patients imaged by different OCT machiness.