Retinal nerve fiber layer thickness in amnestic mild cognitive impairment: Case-control study and meta-analysis

INTRODUCTION: Retinal structural changes in subjects with mild cognitive impairment (MCI) remain a subject of controversy. METHODS: We investigated the correlation between optical coherence tomography (OCT) of the retinal sublayers, including the retinal nerve fiber layer (RNFL), and cognitive function in subjects with amnestic MCI and compared the OCT findings with matched controls. We also performed a meta-analysis of the world literature using a random-effects model. RESULTS: We found no statistically significant differences in OCT between amnestic MCI (aMCI) and controls. In aMCI subjects, we found an inverse relationship between RNFL thickness and two cognitive tests (delayed story recall and a word-list learning test and the word-list test). The meta-analysis revealed a statistically significant decrease in RNFL thickness in MCI subjects. DISCUSSION: The inverse relationship between cognitive testing and RNFL thickness suggests that retinal involvement may include paradoxically increased thickness of the RNFL, which could suggest gliotic reactive changes.