Longitudinal Natural History Study of Retinal Function in Eyes of Patients With Diabetes

Key Inclusion Criteria: * Age ≥ 18 years * Diagnosed with Type 1 or Type 2 diabetes or non-diabetic control patients * Best corrected visual acuity 20/32 or better (Snellen) (≥74 ETDRS letters) * Meets criteria for one of the defined observational groups below * Able and willing to provide informed consent Key Exclusion Criteria: * Ocular or systemic condition, aside from diabetes mellitus (DM), that is likely to affect the assessment of DRSS, DME, or the functioning of the neural retina * Previous treatment of any kind for diabetic retinopathy or DME * Any condition that may preclude adequate imaging of the macula (e.g. dense cataract or other media opacity, ptosis) * History of rhegmatogenous retinal detachment or macular hole * History of vitrectomy * Intraocular surgery (including cataract surgery) within 4 months prior to enrollment or anticipated within the next 6 months * Requiring treatment for DR/DME in the next 6 months