Inclusion Criteria:  Patient managed at the cognitive neurology center for cognitive impairment with a defined LP indication for the assessment of CSF AD biomarkers according to French National Health Agency recommandations in a clinical practice setting Patients with National Health Insurance coverage Patients willing to participate to the research and sign informed consent  Exclusion Criteria:  Patient refusing to participate to research or unable to sign informed consent Patients without indication or displaying contraindication of LP  Chronic retinal pathology interfering with analysis :  chronic glaucoma diabetic retinopathy severe hypertensive retinopathy Contraindication to brain MRI Other pathology considered as severe and impairing life expectancy