Optina Diagnostics' Cerebral ß-Amyloid Status (CAS) Test

Inclusion Criteria: * Male and female adults aged 50 years and older (inclusive). * Individuals with reported cognitive complaint (self or from an informant) under clinical investigation by a health professional for cognitive impairment where Alzheimer's disease (AD) is one of the differential diagnoses. * Demonstrated cognitive impairment as evidenced by at least one of the following: 1. Mini Mental State Examination (MMSE) score \< 26/30 2. Montreal Cognitive Assessment (MoCA) score \< 26/30 3. Score \> 1 Standard Deviation below population mean on a standardized neuropsychological test (in any domain), based on normative data from age-, sex-, education-, and where possible, race-matched peers \[Based on guidelines for detecting Mild Cognitive Impairment due to AD (Albert et al., 2011)\] * Clinical laboratory assessment (complete blood count \[CBC\], standard blood chemistry profile, thyroid stimulating hormone \[TSH\], vitamin B12) within the 6 months prior to enrollment. * Cognitive impairment on the above test/s is unable to be fully explained by systemic, neurological or psychiatric disorders other than Alzheimer's disease. * Capacity to give informed consent by patient or substitute decision maker. * Ability to undergo PET and MRI scans. Exclusion Criteria: * Any ophthalmologic condition that would prevent obtaining retinal imaging and/or could interfere with the analysis of the MHRC images by the CAS, including: 1. Pupil dilation contraindicated (due to a pathology, or presence of 3 quadrants with Van Herick grading of 0 or 1 without iridotomy) 2. Inadequate pupil dilatation (\< 6mm diameter) preventing uniform illumination of the retina with the MHRC 3. Diagnosis of glaucoma or signs of glaucoma (excavation ratio ≥0.7) 4. Signs of vascular occlusion or retinopathy (microaneurysm, exudate, hemorrhage or edema) within a diameter of 10 mm from the mid-point between the optic nerve head and the macula 5. Presence of drusen and/or age-related macular degeneration (AREDS 9-step scale ≥4 - cumulative drusen area diameter ≥ 250 um, pigmentary changes and cumulative drusen area diameter ≥ 63 um or pigmentary changes and cumulative geographic atrophy area diameter ≥ 354 um) 6. Macular anomaly (e.g., macular hole, dystrophy, degeneration) 7. Nuclear sclerosis \> 2 (LOCS II four-point grading system) or presence of central cortical or central posterior subcapsular cataract 8. Refractive error outside the range of -15 D to +15 D 9. Scar, atrophy, naevus, tumor, eepiretinal membrane or retinal pucker with a cumulative area \> 1 disc area within a diameter of 10 mm from the mid-point between the optic nerve head and the macula 10. Papilledema 11. Deficient visual fixation (inability to fixate for at least 2 s) 12. Corneal or media opacities (e.g., Weiss ring) affecting retinal imaging on a cumulative area \> 1 disc area within a diameter of 10 mm from the mid-point between the optic nerve head and the macula (i.e., the area of interest for the MHRC imaging) * Inability of obtaining at least 3 images of satisfactory quality with the MHRC per the Optina Diagnostics quality index software and /or per the eye specialists' evaluation. * Impossibility of obtaining a satisfactory quality amyloid-PET scan for interpretation by imaging specialists. * Individuals who currently or have previously taken cerebral amyloid modifying medication.