Optimal OCT scan diameter identified for evaluating myopic RNFL changes

In myopic eyes, retinal nerve fiber layer thinning (RNFLT) primarily affects the nasal quadrants, and a 4.1 mm optical coherence tomography (OCT) scan diameter performs best for distinguishing myopia-related changes from glaucoma, according to a recent study.

The study evaluated 204 eyes, including 41 controls, 44 with mild myopia, 66 with moderate myopia, and 53 with high myopia. Spectral-domain OCT imaging was performed using 3 concentric circumpapillary scan diameters centered on the Bruch’s membrane opening: 3.5 mm (C1), 4.1 mm (C2), and 4.7 mm (C3).

RNFLT measurements decreased significantly as scan diameter increased (P < 0.001), with the most pronounced thinning observed in the nasal-superior (NS) and nasal-inferior (NI) quadrants. Among the 3 scan sizes, the 4.1 mm (C2) diameter demonstrated the highest and most consistent ability to differentiate myopic from control eyes, particularly in the NI (P = 0.001) and NS (P = 0.014) sectors.

A progressive shift in OCT color-code classifications from green to yellow or red was observed with increasing myopia and larger scan diameters. This shift was most prominent at the outer 4.7 mm ring (C3), where the temporal-inferior quadrant showed a significant increase in yellow classifications (P = 0.020).

Repeated-measures ANOVA identified significant between-group differences in the NS and NI sectors (P < 0.01), as well as significant interactions between myopia group and scan diameter in the NS and temporal-superior regions (P < 0.05).

Reference
Gültekin Irgat S, Demirel R, Ulutürk E, et al. Avoiding False-Positive Glaucoma Diagnosis in Myopic Eyes: Clinical Importance of OCT Scan Diameter. J Clin Med. 2026;15(4):1669. doi: 10.3390/jcm15041669. PMID: 41753357.