The relationship between the degree of cognitive impairment and retinal nerve fiber layer thickness.

The goal of the present study is to investigate the relationship between the degree of cognitive impairment and retinal nerve fiber layer (RNFL) thickness which is measured by the optical coherence tomography (OCT). Thirty-five patients with Alzheimer's disease (AD), 35 patients with mild cognitive impairment (MCI), and 35 healthy volunteers, between the ages of 60-87, who were examined in the neurology outpatient clinic among 2012-2013 were prospectively involved in our study. Mini mental state examination (MMSE) test, montreal cognitive assessment (MOCA), and also neuropsychological test batteries were used for the neurocognitive evaluation. RNFL thickness was measured by the OCT technique and the differences among groups were studied. The relationship between RNFL thickness and MMSE scores with demographic characteristics was investigated. RNFL thickness was significantly lower in AD and MCI groups compared with the control group (p < 0.01). No significant differences of RNFL were found between the MCI and the AD groups (p > 0.05). Significant correlation was found between MMSE scores and the RNFL values (p < 0.05). Significant thinning in RNFL along with age was detected (p < 0.05). In our study, it is thought that retinal nerve fiber degeneration and central nervous system degeneration may be concurrent according to the thinning of RNFL measured by OCT in AD and MCI groups. RNFL measurement may also be useful for early diagnosis and evaluation of the disease progression. Further studies are needed to optimize the utility of this method as an ocular biomarker in AD.