This study investigated the effect of image quality fluctuations on the repeatability of thickness measurements of the peripapillary retinal nerve fibre (PP-RNFL) and ganglion cell-inner plexiform (GC-IPL) layers using swept-source optical coherence tomography (SS-OCT). Three consecutive OCT scans each were performed on 56 healthy subject. Finally, 168 SS-OCT results were analysed. Based on the tertile values of the mean absolute difference of image quality score, all subjects were divided into the following three groups—low-(LIQD), moderate-(MIQD), and high-(HIQD) image quality score difference groups. A linear mixed model and intraclass correlation coefficients (ICCs) were used for analyses. Despite high ICC values (> 0.9), several sectors showed significant differences in the ICC values in intergroup comparisons. For LIQD-HIQD and MIQD-HIQD, most PP-RNFL sectors showed significant differences. For GC-IPL sectors, the LIQD-HIQD comparison showed significant differences in the temporosuperior (p = 0.012), inferior (p <.001), and temporoinferior (p = 0.042) sectors. Significant differences existed in the average GC-IPL (p = 0.009), nasoinferior (p = 0.035), and inferior GC-IPL sectors (p <.001) for MIQD-HIQD comparison. With higher image quality fluctuations, the repeatability of SS-OCT decreased in several sectors, which are considered clinically relevant in evaluating glaucoma status. Therefore, maintaining high-quality image status is essential to enhance the reliability of SS-OCT.
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