Corneal confocal microscopy as a tool for detecting axonal degeneration in multiple sclerosis and correlation with severity: A meta-analysis.

Objective: This study explores the role of corneal confocal microscopy (CCM) in detecting axonal degeneration in people with multiple sclerosis (pwMS) and its correlation with severity.

Methods: A literature search was conducted across PubMed, Scopus and Google Scholar. Differences in corneal nerve fiber density (CNFD), corneal nerve fiber branch density (CNBD), corneal nerve fiber length (CNFL), between pwMS and healthy controls were quantified using risk ratio (RR) and estimated using random effects models due to high observed heterogeneity. Random-effects meta-regression was utilized to evaluate the relationship between severity and CNFD, CNFL and CNBD.

Results: A total of 8 studies were included with 351 pwMS. CNFD and CNFL were lower in pwMS compared to controls (Hedge's G Effect Size = -1.53, 95 % CI:2.62, -0.44, p = .01). Meta-regression analysis showed that CNFD (Mean b = -1.93, 95 % CI (-3.32, -0.55), p = .01), CNBD (Mean b = -33.36, 95 % CI (-48.90, -17.82), p < .01) and CNFL (Mean b = -2.31, 95 % CI (-2.94, -1.68) p < .01) had significant associations with Multiple Sclerosis Severity Score (MSSS) but not with Extended Disability Severity Score (EDSS).

Conclusions: CCM can be a non-invasive imaging biomarker for axonal degeneration in pwMS.