Evaluation of Multiple Sclerosis patients with corneal confocal microscopy and retinal optical coherence tomography

Purpose: This study aimed to assess structural alterations in the retinal nerve fiber layer and corneal subbasal nerve plexus of patients with Multiple Sclerosis (MS) through optical coherence tomography (OCT) and in vivo corneal confocal microscopy (IVCCM). Furthermore, it explored the relationship of these parameters with disease duration, Expanded Disability Status Scale (EDSS) scores, MS subtype, and a history of optic neuritis (ON). Materials and Methods: This cross-sectional study included 98 eyes from 49 patients diagnosed with MS and 82 eyes from 41 healthy controls, all of whom were followed up at Van Yüzüncü Yıl University Dursun Odabaş Medical Center. Following a detailed ophthalmologic examination, spectral domain OCT (Heidelberg Spectralis®) was used to assess retinal structures, and confocal microscopy (Heidelberg Retina Tomograph 3 - Rostock Cornea Module) was used to evaluate corneal subbasal nerve fibers. OCT measurements included peripapillary retinal nerve fiber layer (RNFL), and macular NFL, ganglion cell layer (GCL), inner plexiform layer (IPL), and ganglion cell complex (GCC). IVCCM was used to assess corneal nerve fiber density (CNFD), nerve branch density (CNBD), nerve fiber length (CNFL), and tortuosity coefficient (TC). The findings were compared based on disease duration, EDSS, MS subtype, medication use, and ON history. Results: CNFD, CNBD, and CNFL values were significantly lower in the MS group compared to controls (p<0.05), whereas TC did not show a statistically significant difference (p>0.05). Significant thinning was observed in the RNFL, GCL, IPL, and GCC layers in MS patients. These reductions were more pronounced in the SPMS group and in patients with a history of ON. A significant negative correlation was identified between disease duration and RNFL, GCL, IPL, and GCC measurements (p<0.05), but no significant correlation was found between IVCCM parameters and disease duration or EDSS. Comparisons across MS subtypes showed significantly lower GCL, GCC, and RNFL values in the SPMS group (p<0.05), while no significant differences were observed in IVCCM metrics. EDSS scores were negatively correlated only with the global, temporal, and nasal superior RNFL segments. Conclusion: Structural changes observed in retinal and corneal layers reflect the neurodegenerative nature of MS. Although IVCCM was not able to distinguish between MS subtypes, OCT and IVCCM measurements may serve as potential biomarkers for monitoring disease progression in MS. Further prospective studies with larger sample sizes, particularly with more SPMS patients, are warranted to validate these findings. Keywords: Multiple Sclerosis, Optical Coherence Tomography, In Vivo Corneal Confocal Microscopy, RNFL, Ganglion Cell Complex, Neurodegeneration