Inclusion Criteria:

• Age ≥ 18 and < 80 years
• Diagnosis of type 2 diabetes mellitus, falling into one of the following categories:
  • For Group 1 participants with DR Severity level 10 to 20 the patient must have been diagnosed ≥15 years ago. If diagnosis of diabetes was <15 years, the participant is not eligible. 
  • Any amount of time if DR Severity level ≥ 35 (Groups 2-4) 
    • Any one of the following will be considered to be sufficient evidence that diabetes is present: 
      • Current regular use of insulin for the treatment of diabetes.
      • Current regular use of oral anti-hyperglycemia agents for the treatment of diabetes.
      • Documented diabetes by American Diabetes Association and/or the World Health Organization criteria.
  • OR
  • Group 5 participants (non-diabetic control group), recruited only from a subset of select sites, must have generally good health in the opinion of the investigator, no history of documented diabetes or diabetes-related condition, HbA1c levels < 5.7 as confirmed by the central laboratory, must meet none of the exclusion criteria listed below, and must have no evidence of retinal diseases on color fundus photos or OCT.
• Media clarity, pupillary dilation, and study participant cooperation sufficient to obtain adequate fundus photographs, FA, and OCT.
  • Investigator must verify accuracy of OCT scan by ensuring it is centered and of adequate quality (including segmentation line placement)
• Able and willing to provide informed consent and participate (i.e., proficient in written and  spoken English, Spanish or other IRB-approved consent language; has the capacity to consent for one’s own self).
• Able and willing to provide genetics sample

Exclusion Criteria:

• A condition that, in the opinion of the investigator, would preclude participation in the study such as unable or unwilling to complete all study procedures.
• Participation in an investigational trial that involved treatment within last 30 days, with the exception of the parent Protocol AF.
• Known allergy to fluorescein dye.
• Participant has any retinal condition that complicates the diagnosis and grading of DR (e.g.,previous therapies (vitreo-retinal surgery, photodynamic therapy)) or participant shows signs of retinal diseases other than DR.
  • Prior procedures to treat DR (e.g., intraocular anti-VEGF, vitrectomy) are not  exclusionary so long as they do not interfere with the evaluation and grading of DR;participants with history of PRP are excluded since the study does not include DR severityof 60
• Participant is currently taking or has been taking a PPAR-agonist within the last 90 days.
• Participant is currently taking a serine or glycine supplement or has been taking a serine or glycine supplement within the last 60 days
• Employed in an involved research department or ophthalmologic practice participating in this research.
• People who are currently pregnant and/or lactating.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 09/10/2024. Questions regarding updates should be directed to the study team contact.