Study On Correlation Between Retinal Structure And Multimodal Imaging In Patients With Alzheimer’s Disease

Objective: Alzheimer’s disease(AD)is the most common type of senile dementia.Research on the early diagnosis of AD is of great significance to delay the progression of the disease.At present,there are many researches on retinal structural changes as biomarkers for the early diagnosis of AD at home and abroad.However,the mechanism of fundus retinopathy in AD patients remains to be discovered.This study aims to explore the possible mechanism of retinopathy in AD patients from three aspects: brain volume,integrity of white matter fiber bundles in visual pathway and function of neurons in primary visual cortex by combining fundus imaging and multimodal imaging techniques.Methods: In this study,39 AD patients and 39 normal controls were enrolled.Retinal images were obtained by optical coherence tomography,and retinal thickness of each layer and fundus perfusion density were segmtured and calculated.Magnetic resonance images of various sequences(three-dimensional T1 weighted imaging,diffusion tensor imaging,resting-state f MRI)were collected,and region of interest volume was partitioned and estimated by Freesurfer software.The white matter fiber tracts of visual pathway were displayed by probabilistic tractography,and diffusion parameters of DTI of visual pathway and neuronal activity indexes of primary visual cortex were calculated.The differences of retinal structure and multimodal imaging parameters between the two groups were compared,and the correlation between retinal structure and multimodal imaging was discussed by Spearman correlation analysis.Results: 1)Analysis of differences in retinal structure and multimodal imaging parameters showed that compared with the normal controls group,the average macular thickness,macular volume,macular ganglion cell layer(GCL)、inner plexiform layer(IPL)、outer nuclear layer(ONL)、temporal peripapillary retinal nerve fiber layer(p RNFL)thickness of AD patients were significantly thinner(p<0.05);the relative volume of the hippocampus and the relative volume of the lateral geniculate body were significantly decreased in AD patients(p<0.0001);the fractional anisotropy(FA)of the optic tract and optic radiation in AD patients was decreased(p<0.05);The amplitude of low frequency fluctuations(ALFF)and fractional ALFF(f ALFF)of the primary visual cortex in AD patients were decreased,but the difference was not statistically significant(p>0.05).2)Correlation analysis between retinal structure and multimodal imaging showed that hippocampal volume of AD patients was positively correlated with mean macular thickness(rs=0.327,p=0.043),GCL thickness(rs=0.360,p=0.025),IPL thickness(rs=0.330,p=0.040)and temporal p RNFL thickness(rs=0.384,p=0.019).The optic tract FA value of AD patients was positively correlated with macular volume(rs=0.453,p=0.0001),GCL thickness(rs=0.603,p=0.0004)and IPL thickness(rs=0.564,p =0.006).FALFF value of primary visual cortex was positively correlated with macular volume(rs=0.327,p=0.045)and temporal p RNFL thickness(rs=0.463,p =0.004)in AD patients.3)In the multilinear model,after adjusting for age and dementia degree,optic tract FA of AD patients was significantly correlated with GCL thickness(β = 0.456,p = 0.005),IPL thickness(β = 0.437,p = 0.009),and macular volume(β = 0.357,p = 0.033).FALFF value of primary visual cortex(β = 0.380,p = 0.041)and hippocampal volume(β = 0.404,p =0.036)were correlated with temporal p RNFL thickness in AD patients.Conclusion: Retinal structure is related to the integrity of white matter fiber tracts in the visual pathway and the functional metabolism of primary visual cortex and hippocampal volume in AD patients.