• Men or non-pregnant women (on acceptable contraception) with T1D\* according to standard criteria:

⁃ T1D defined as either (1) T1D diagnosed below 40 years of age and insulin therapy commencing within one year of T1D diagnosis, or (2) T1D diagnosed before, at or after 40 years of age along with: i) Documented history of ketoacidosis, and/or ii) Documented history of very low or undetectable C-peptide (fasting \<200 nmol/L or 0.2 pmol/L), and/or iii) Documented history of T1D related autoantibody/ies (anti-Glutamic acid decarboxylase, anti-A2, anti-ZnT8).

• Age 18 years or over;

• Estimated glomerular filtration rate (eGFR) must exceed 30 ml/min/1.73m2;

• Must have at least one eligible eye with non-proliferative retinopathy (ETDRS score 35-53 inclusive) confirmed by current retinal photography within the last 3 months (irrespective of prior laser therapy). Note: Any eye having undergone prior pan-retinal laser therapy is not eligible, but prior focal, macular or grid laser does not exclude that eye from eligibility.;

• All types of insulin therapy, with no restriction by level of HbA1c;

• Willing and able to comply with all study requirements, including treatment, assessment and clinic visit attendances;

• Able to personally read and understand the Participant Information and Consent Form and provide written, signed and dated informed consent to participate in the study.

‣ Eligibility criteria for the reference group is limited to age and gender matched individuals who do not have T1D.