Perifovea retinal thickness as an ophthalmic biomarker for mild cognitive impairment and early Alzheimer's disease

Introduction The aim of this study was to investigate retinal thickness as a biomarker for identifying patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Methods The retinal thickness, utilizing the spectral domain optical coherence tomography, was compared among 73 patients with AD, 51 patients with MCI, 67 cognitive normal control (NC) subjects. Results The retinal thickness of ganglion cell complex and peripapillary retinal nerve fiber layer decreased in both AD and MCI patients, in comparison with NC subjects (AD vs. NC, P < .01; MCI vs. NC, P < .01). The inner retinal layers in macular area in MCI exhibited significant thinning compared with NC (P < .001). Remarkable association was found between the retinal thickness and brain volume (P < .05). Better correlation was seen between the inner perifovea retinal thickness and the hippocampal and entorhinal cortex volume (r: 0.427-0.644, P < .01). Discussion The retinal thickness, especially the inner retinal layer thickness, is a potentially early AD marker indicating neurodegeneration.