Evaluation of the relationship between retinal neurodegeneration and cognitive functions in dementia patients with PET-CT

Alzheimer's Disease (AD) affects more than 46.8 million people worldwide; It is estimated that this number will reach 131.5 million in 2050. Due to the increasing prevalence of AD on a global scale, low-cost and easy-to-apply biomarkers that can be applied to the general population are being investigated. In our study, we aimed to investigate the diagnostic value of optical coherence tomography (OCT), which is a low-cost, easy-to-apply and accessible imaging method, in AD. A total of 62 individuals, including patients diagnosed with mild dementia due to AD according to DSM-5 diagnostic criteria and the diagnostic criteria published by the National Institute of Aging-Alzheimer's Association (NIA-AA), and volunteers without cognitive impairment as the control group, were included in the study. Individuals in the patient and control groups were evaluated with the Standardized Mini Mental Test (SMMT), which was determined according to their educational status. In addition, the Clinical Dementia Rating Scale (KDS) was applied to the individuals in the patient group. Detailed ophthalmological examinations and optical coherence tomography (OCT) examinations of all study participants were performed. Retinal nerve fiber layer (RNFL) thickness was measured by OCT and comparisons were made between groups. Individuals in the patient group were imaged with FDG-PET and hypometabolism in regions considered typical of AD (precuneus, posterior cingulate cortex, parietal cortex, temporal cortex) was determined. The relationship between regions with hypometabolism on PET and quadrants with thinning of RNFL thickness on OCT was investigated. When the correlation between the results obtained with these two imaging methods is evaluated; A statistically significant, positive, moderate correlation was determined between the thinning of the RNFL thickness in the right eye superior temporal (ST) quadrant and the right and left precuneus, right and left superior parietal cortex, and left inferior parietal cortex (p<0.05). A statistically significant, positive, moderate correlation was found between right eye mean RNFL thinning and right and left superior parietal cortex (p<0.05). A statistically significant, positive, moderate correlation was determined between the thinning of the RNFL thickness in the left superior nasal (SN) quadrant and the right and left precuneus, right and left superior parietal cortex, and right and left posterior cingulate cortex (p<0.05) . A statistically significant, positive, moderate correlation was found between the left eye mean RNFL thinning and left superior parietal cortex (p<0.05). As a result, in our study; We found a significant, positive and moderate correlation between hypometabolism detected in areas considered typical for AD on FDG PET and quadrants with thinning of RNFL thickness on OCT (p<0.05), a marker of OCT in the diagnosis of AD. supports the hypothesis that