Applying Retinal Vascular Structures Characteristics Coupling With Cortical Visual System In Alzhemer’s Disease Spectrum Patients

Background: Alzheimer’s disease(AD)is the most common neurodegenerative disease and the leading cause of dementia worldwide.An estimated 47 million people worldwide are living with dementia,and the number is expected to reach 131 million by 2050.AD patients mainly present with multi-dimensional cognitive dysfunction such as episodic memory,executive function and attention function.However,early AD and its high-risk Mild cognitive impairment(MCI)are often accompanied by visual impairment,particularly impairment in contrast sensitivity,visuospatial ability,and perception of faces,objects,scenes,and colors.These studies further suggest that visual impairment features in AD spectrum patients can be helpful for early recognition,progression monitoring,and prognosis determination.Among the main visual pathways,visual cortical changes are of great value for early diagnosis and progression monitoring of AD.Changes in the functional network of the visual system from normal aging to AD progression can be used as biomarkers to predict AD progression.Therefore,the use of f MRI technology to evaluate the damage characteristics of visual pathways and their evolution with disease progression will become a research hotspot in the field of AD.This study explored the association between cortical visual system and retinal vascular structures in ADspectrum patients,and it established a screening tool to perceive the preclinical AD based on these parameters identified in the retinal examination.Methods: A total of 42 subjects were enrolled and were distributed two groups: 22 in patients of cognitive impairment and 20 healthy control.In these subjects,f MRI data were used to extract the correlation between the normal population and the cognitive impairment population and the visual circuit correlation between the different brain area values and retinal vascular density,perfusion density,FAZ area,FAZ visual field meter,optic disc area,average cup-to-disc ratio,vertical cup-to-disc ratio,cup volume,RNFL and other data,thereby revealing the significance of visual impairment as a biomarker for predicting the progression of Alzheimer’s disease.The functional connection between the cortical visual system and the retinal vascular structure was further explored.Results: This study found that the cognitive impairment group displayed prominently decreased functional connectivity of cortical visual system mainly involving the right inferior temporal gyrus,left supramarginal gyrus and right postcentral gyrus.Meantime,we observed retinal vascular structures characteristics was becoming deteriorated with the declining of functional connectivity in cortical visual system.We found that the functional connection strength of the left marginal superior gyrus in the cortical visual system in the cognitive impairment group was significantly correlated with some retinal vascular structures,such as inner layer vascular density(6x6mm;r = 0.480,P = 0.024),outer vascular density(6x6mm;r =0.454,P = 0.034),and complete vascular density(6x6mm,r = 0.444,P = 0.038),while the functional connection strength of the right posterior central gyrus was significantly positively correlated with inner perfusion density(3x3mm;r = 0.489,P = 0.021)and complete perfusion density(3x3 mm;r = 0.478,P = 0.024).The strength of the functional connection of the right inferior temporal gyrus in the visual network of healthy control subjects was significantly positively correlated with some measurements of vascular density and perfusion density.Specifically,there was a correlation between the functional connection strength of the right inferior temporal gyrus and the density of inner layer(3x3 mm;r = 0.620;p = 0.004),complete vascular density(3x3 mm;r = 0.622,p = 0.003),central perfusion density(3x3 mm;r = 0.517,p =0.020),inner perfusion density(3x3 mm;r = 0.531,p = 0.016),complete perfusion density(3x3mm;r = 0.544,p = 0.013),and inner perfusion density(6x6 mm;r = 0.452,p = 0.045).Conclusion: Our research findings demonstrate that individuals who suffer from cognitive impairment exhibit a substantial decline in functional connectivity in the cortical visual system,particularly in the right inferior temporal gyrus,superior left marginal gyrus,and right posterior central gyrus.Furthermore,our results indicate that the deterioration of retinal vascular structural features is positively associated with a reduction in functional connectivity of the cortical visual system.This investigation contributes novel insights into the aberrant cortical visual system in patients with cognitive impairment,underlining the crucial role of retinal vascular structural features as potential biomarkers for the diagnosis and monitoring of Alzheimer’s disease.Further studies will focus on carrying out more extensive longitudinal follow-up studies.