Visual system involvement in Alzheimer’s disease

Abstract

To assess in Alzheimer’s disease (AD) patients the Visual System functioning through full field Visual Evoked Potentials (VEPs) and to measure neuro-retinal thickness through Optical Coherence Tomography (OCT), in particular the peripapillary Retinal Nerve Fiber Layer (RNFL) thickness and macular Ganglion and Inner Plexiform Layers (GCL and IPL) volume, in order to find new reproducible diagnostic markers and outcome measures. 145 subjects were enrolled (49 with AD, 39 with Mild Cognitive Impairment (MCI) and 57 controls, HC), receiving an OCT scan acquisition and Visual Evoked Potentials (VEPs) in 36 AD, 25 MCI and 39 HC at baseline. Nineteen AD and 23 MCI underwent a follow up OCT scan. At baseline peripapillary RNFL, global and in superior quadrant, was significantly thinner in AD and MCI patients than in HC. Macular GCL was significantly thinner in AD than in MCI and HC. A positive association was found between OCT and neuropsychological tests. Over time AD patients showed a significantly higher decay in RNFL thickness than MCI subjects. Furthermore, RNFL, GCL and IPL thinning seemed to be associated with worsening in cognition. Our findings confirm that the Visual System is involved in AD and OCT is as a possible marker of disease severity.