Reproducibility of retinal nerve fiber layer thickness measurements using spectral domain optical coherence tomography

Abstract

Purpose: To evaluate the reproducibility of the peripapillary retinal nerve fiber layer (RNFL) thickness measurements obtained by Spectralis spectral domain optical coherence tomography (OCT) (Heidelberg Engineering, Heidelberg, Germany) in normal and glaucoma participants.

Methods: Participants were recruited from a university-based clinic. Peripapillary RNFL thickness measurements were repeated 3 times during the same visit using the follow-up function. One eye of each participant was randomly selected for statistical analysis. Reproducibility was evaluated using within-subject standard deviation (Sw), coefficient of variation (CV), and intraclass correlation coefficient (ICC). Spearman rank correlation coefficient analyses were used to assess the correlation of the standard deviation of the 3 measurements for each participant with the RNFL thickness value.

Results: Forty-five normal participants and 33 glaucoma patients were included in the study. The CVs ranged from 1.45% [overall global (G)] to 2.59% [temporal quadrant (T)] in normal eyes and from 1.74% (G) to 3.22% (T) in the glaucomatous eyes. ICCs ranged from 0.977 (T) to 0.990 (G and inferior-nasal sector) in normal eyes and from 0.983 (T) to 0.997 (inferior quadrant) in glaucomatous eyes. Sw were from 1.34 μm (G) to 2.39 μm (superior-temporal and inferior-temporal sectors) in normal eyes and from 1.14 μm (G) to 2.25 μm (superior-nasal sector) in the glaucomatous eyes. There were no significant correlations between RNFL thickness values and the measurement variability for each participant.

Conclusions: Spectralis OCT shows excellent reproducibility for measuring the peripapillary RNFL thickness values in both healthy and glaucoma participants.

Figure 1

Example of the second peri-papillary retinal nerve fiber layer (RNFL) circular scan centered on the optic nerve head (ONH) using Spectralis optic coherence tomography (OCT) in a normal eye after applying the follow-up function. The graph on the lower right of the window presents the RNFL thickness detected along the circular scan (black curve), compared to values from the normative database (green curve). The gray curve indicates the values of the chosen reference scan. The black values in the pie chart (lower left) give the average RNFL thickness value for each sector as well as the global average (G). N - nasal; T - temporal; TS - superior-temporal; TI - inferior-temporal; NS - superior-nasal; NI - inferior-nasal

Figure 2

Figure showing the relationship between the overall global Spectralis optic coherence tomography (OCT) peri-papillary retinal nerve fiber layer (RNFL) thickness measurements versus variability (SD) of 3 repeated measurements. There was no relationship between variability (SD) and overall global RNFL thickness (Spearman r = −0.063, P = 0.582). SD – standard deviation.