The relationship between retinal layer thickness and cognition in patients with multiple sclerosis: A systematic review of current literature

Background: This study was conducted to evaluate the relationship between retinal layer thickness (RLT) and cognition in patients with multiple sclerosis (MS). Methods: We searched PubMed, Scopus, Embase, Web of Science, and Google Scholar. The search strategy included the MeSH and text words as [“ora serrata” OR “retina” OR (“coherence tomography” AND “optical”) OR “OCT tomography” OR (tomography AND OCT) OR “optical coherence tomography” OR “OCT” OR “retinal thickness” OR “inner plexiform layer” OR “nerve fiber layer” OR “ganglion cell layer” OR “inner nuclear layer” OR “outer plexiform layer” OR “outer nuclear layer” OR “external limiting membrane” OR “inner segment layer” OR “outer segment layer” OR “retinal pigment epithelium”] AND [“cognition”* OR “cognitive function”* OR (function* AND cognitive)] AND [(sclerosis AND multiple) OR (sclerosis AND disseminated) OR "disseminated sclerosis" OR "multiple sclerosis" OR "acute fulminating"]. Results: The literature search revealed 1090 articles; after deleting duplicates, 980 remained. Finally, 14 studies were included. Totally, 1081 patients were evaluated. Mean age ranged from 31 to 55 years. In some studies, there was a correlation between cognition and retinal thickness, while others did not confirm this finding. Some authors found cognitive impairment (CI) in patients with MS with RLT. Conclusion: The results of this systematic review show that there are discrepancies between the results of studies regarding the relationship between RLT and cognition status in patients with MS. Further studies with more included original studies and meta-analysis are recommended.