Analysis of changes in the macula and retinal nerve fiber layer by optical coherence tomography in patients with Alzheimer’s disease (AD) (original) (raw)

2012, Acta Ophthalmologica

the retina is an attractive source of biomarkers since it shares many features with the brain. thickness differences in 10 retinal layers between 19 patients with mild Alzheimer's disease (AD) and a control group of 24 volunteers were investigated. Retinal layers were automatically segmented and their thickness at each scanned point was measured, corrected for tilt and spatially normalized. When the mean thickness of entire layers was compared between patients and controls, only the outer segment layer of patients showed statistically significant thinning. However, when the layers were compared point-by point, patients showed statistically significant thinning in irregular regions of total retina and nerve fiber, ganglion cell, inner plexiform, inner nuclear and outer segment layers. Our method, based on random field theory, provides a precise delimitation of regions where total retina and each of its layers show a statistically significant thinning in AD patients. All layers, except inner nuclear and outer segments, showed thickened regions. new analytic methods have shown that thinned regions are interspersed with thickened ones in all layers, except inner nuclear and outer segments. Across different layers we found a statistically significant trend of the thinned regions to overlap and of the thickened ones to avoid overlapping. Alzheimer's disease (AD) is an increasing health issue for elderly people and healthcare services in developed countries. There is wide agreement about the relevance of its early detection, leading to interest in early, convenient and affordable biomarkers. The brain is the main tissue affected in AD, and the retina is the only neuronal tissue that can be analyzed non-invasively in AD. Increasing evidence suggests that retinal analysis can provide insights into brain pathology. In a sample of 2,124 patients with mild AD, Mutlu et al. found that a thinner ganglion cell layer (GCL), nerve fiber layer (NFL) and inner plexiform layer (IPL) are associated with smaller grey matter, white matter and hippocampal volume 1. Ong et al. found that thinner total retinal thickness is associated with smaller grey matter volume only in the temporal lobe, whereas thinner GC-IPL complex is associated with smaller grey matter and white matter volumes in the temporal lobe, as well as smaller grey matter volume in the occipital lobe 2. Casaletto et al. found thinner retinal thickness and GCL to be related to medial temporal lobe atrophy 3. In a homogeneous sample of patients with early-stage AD, Salobrar-Garcia et al. 4 found that peripapillary total retinal thinning accompanies AD development. More recently, our group has found that retinal thinning in the macular area appears at a very early stage of AD 5 , together with a 40% decrease in contrast sensitivity 6. All these findings converge to demonstrate that the volume of brain structures involved in AD is related to retinal thickness and visual function. This suggests that AD-associated neuronal damage and deposits may occur in the retina before they occur in the brain, implying that retinal analyses could allow AD detection during the asymptomatic preclinical period 7,8. Ten retinal layers were segmented and studied: nerve fiber layer (NFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), inner