Relationship between Cognitive Impairment and Retinal Morphological and Visual Functional Abnormalities in Alzheimer Disease

Abstract

There is conflicting evidence as to whether Alzheimer disease (AD) is accompanied by loss of retinal ganglion cells. To evaluate this issue, we have used optical coherence tomography (OCT) to assess the thickness and volume of the retina. We have also sought to correlate our findings with visual function and cognitive impairment. We evaluated 28 eyes of 14 patients with AD and 30 eyes of 15 age-matched control subjects. In these two groups, we measured retinal nerve fiber layer (RNFL) thickness, macular thickness, and macular volume with OCT, visual function through latency of the pattern visual evoked potential (VEP) signal, and cognitive impairment through the Mini-Mental State Examination (MMSE). The parapapillary and macular RNFL thickness in all quadrants and positions of AD patients were thinner than in control subjects. The mean total macular volume of AD patients was significantly reduced as compared with control subjects (P < 0.05). Total macular volume and MMSE scores were significantly correlated. No significant difference was found in the latency of the VEP P100 of AD patients and control subjects. Our study confirms some other studies in showing that in AD patients there is a reduction of parapapillary and macular RNFL thickness and macular volume as measured by OCT. The reduction in macular volume was related to the severity of cognitive impairment.