Influence of OSCAR-IB criteria on test–retest reliability of Spectralis SD-OCT retinal thickness measurements in people with Multiple Sclerosis

BACKGROUND: Optical coherence tomography (OCT) enables evaluation of inter-eye differences (IEDs) in peri-papillary retinal nerve fiber layer (pRNFL) and macular ganglion cell-inner plexiform layer (GCIPL) thicknesses to identify unilateral optic nerve involvement (UONI), included in the 2024 revised McDonald diagnostic criteria for multiple sclerosis (MS). OBJECTIVES: To evaluate pRNFL and GCIPL thickness test-retest reliability in scans fulfilling (SFO) versus not fulfilling (SNFO) OSCAR-IB criteria in people with MS using Spectralis SD-OCT. METHODS: From 164 participants, two scans per eye per protocol (optic nerve head: pRNFL; macular volume: GCIPL) were obtained with Spectralis SD-OCT and classified as SFO or SNFO. Intra-visit intraclass correlation coefficients (ICCs) and coefficients of variation (COVs) quantified reproducibility. RESULTS: = 97, ICC = 0.990, COV = 0.83%). Algorithm failure and low signal strength most affected pRNFL (COV = 7.72%) and GCIPL (COV = 3.34%) reproducibility, respectively. CONCLUSIONS: OSCAR-IB violations negligibly affected GCIPL reliability, although reduced pRNFL reliability, supporting quality control to avoid erroneous UONI, and suggesting that GCIPL measures may be more robust than pRNFL measures with Spectralis SD-OCT, in contrast to prior Cirrus HD-OCT studies.