Quantitative Analysis of Retinal Nerve Fiber Layer Thickness Using SPECTRALIS Glaucoma Module Premium Edition and SPECTRALIS Standard Glaucoma Module.

PURPOSE

To evaluate the relationship between retinal nerve fiber layer (RNFL) thickness measured by SPECTRALIS Glaucoma Module Premium Edition (GMPE) and SPECTRALIS Standard Glaucoma Module (SGM).

METHODS

This was a cross-sectional study of glaucoma and glaucoma suspect patients from an academic center between May and October 2023. Peripapillary RNFL thickness was measured using GMPE and SGM on the same day; only scans with good centration and reliable segmentation in both modalities were analyzed.

RESULTS

Of 1277 eyes (665 patients) reviewed, 766 eyes (465 patients) met inclusion criteria. Global and sectoral RNFL thicknesses were highly correlated between GMPE and SGM (r ≥ 0.844; ICC ≥ 0.706; P < 0.001 for all); however, global and sectoral RNFL thicknesses between the modules were significantly different (P < 0.001), except for the temporal (P = 0.199) and superotemporal (P = 0.282) sectors. Bland-Altman analysis revealed a global 3.31-µm systematic difference (95% limits of agreement, -7.04 to 13.66); 239 eyes (31.2%) and 63 eyes (8.2%) had a larger than 5-µm and 10-µm difference, respectively. Factors associated with greater absolute measurement differences included higher GMPE RNFL thickness (P < 0.001), lower GMPE scan quality (P = 0.040), and normal-tension glaucoma diagnosis compared to primary open-angle glaucoma (P = 0.028).

CONCLUSIONS

Despite excellent correlation, global RNFL thickness and the RNFL thickness of most sectors differed significantly between GMPE and the SGM, sometimes markedly. Clinicians should consider these differences when interpreting or transitioning between modules in the management of glaucoma patients.

TRANSLATIONAL RELEVANCE

Although highly correlated, GMPE reported thicker global and sectoral RNFL measurements than SGM, which is important when comparing longitudinal OCT follow-up using these modules.