This is a proof of concept observational study is to determine if there is correlation between Aβ plaques and vascular findings in the Retina versus brain ARIA.

Based upon studies and histological evidence, investigators and study sponsor suspects that the primary mechanism that causes CAA in the brain (and increased risk of ARIA) may also occur in the retina. Investigators propose use of both amyloid brain PET imaging, MRI, and retinal imaging to determine if patients undergoing Lecanemab treatment allows for in the ability to correlate ARIA from retinal amyloid and vasculature versus MRI criteria, and a measurable reduction in amyloid in the retina when compared with amyloid PET scans of the brain post-treatment.

Inclusion Criteria:

1. Subjects must be eligible for and intend to receive LEQEMBI under standard of care treatment.
2. Male and female subjects ages ≥50 years old.
3. Must be willing to comply with protocol including pupillary dilation to a minimum of 3.5 mm to allow for ocular imaging.
4. Patient or patient's legally authorized representative (LAR) (e.g., spouse or legal guardian) has the ability to understand the purpose and risks of the study and provide signed and dated informed consent and authorization to use protected health information (PHI) in accordance with national and local patient privacy regulations.

Exclusion Criteria:

1. History of acute angle-closure glaucoma or allergic reaction to the protocol-specified ophthalmic medication for dilation of the pupils.
2. Self-reported or diagnosed history of dense cataracts or other significant media opacity that may affect clear images of the retina.
3. Subjects must not have had eye surgery in the past 2 months, be currently administering eye drops relating to previous eye surgery,
4. Unable or unwilling to comply with the protocol requirements.

Male and female subjects ages 50 and up eligible for treatment with LEQEMBI.