Comparison of the Thickness of the Fiber Layer of the Retinal Nerves in Spectral Domain Optical Coherence Tomography in Normal Eyes Older Than 40 Years.

Purpose: To compare measurements of the thickness of the retinal nerve fibre layer (RNFL) and assess the agreement between three different devices for spectral domain optical coherence tomography.

Material and methods: The RNFL thickness of both eyes of 23 normal subjects older than 40 years was measured using Canon HS100, Topcon Maestro, and NIDEK RS-3000 devices. Both eyes of each subject were scanned in random order. All scans were completed on the same day in the morning. The average and four quadrants (superior, inferior, nasal, and temporal) of RNFL thickness were measured. To determine the differences in RNFL thickness, analysis of variance for repeated measurements was performed. A Bland-Altman plot was plotted, and coefficients of determination were calculated.

Results: A total of 46 eyes of 23 subjects were enrolled in this study. The average RNFL thickness as determined by the three OCT devices was correlated (p < 0.001), but differed significantly between the three devices, as most were quadrant measurements. The mean average RNFL thickness was 98.5 ± 6.6 µm as measured by Canon HS100, 108.5 ± 8.8 µm as measured by Topcon Maestro, and 104.9 ± 9.0 µm as measured by NIDEK RS-3000. Topcon Maestro showed the highest average RNFL thickness value. Bland-Altman plots revealed considerable agreement among the three devices, except for the inferior quadrants between Topcon Maestro and NIDEK RS-3000 measurements. All three devices reveal considerable coefficients of determination values for mean RNFL thickness (0.917 - 0.127).

Conclusion: Although the peripapillary RNFL thickness measurements taken with Canon HS100, Topcon Maestro, and NIDEK RS-3000 were in good agreement, they were not interchangeable in clinical practice, as the values differed significantly.