ARIADNE is a prospective observational cohort study of patients with type 2 diabetes mellitus (T2DM) treated with daily metformin and scheduled to initiate treatment with newer antidiabetic agents, such as sodium-glucose cotransporter 2 inhibitors (SGLT2 inhibitors) and glucagon-like peptide-1 receptor agonists (GLP-1RAs). These newer antidiabetic agents have demonstrated significant benefits in improving glycaemic control; however, some studies suggest that their rapid glucose-lowering effects may be associated with transient worsening or progression of retinal complications.

The purpose of this study is to evaluate the efficacy and safety of newer antidiabetic agents on retinal vasculature and visual acuity, and to investigate how these changes are associated with alterations in markers of peripheral endothelial and cardiovascular function.

The investigators will study individuals with type 2 diabetes mellitus (T2DM), diagnosed according to the criteria established by the European Association for the Study of Diabetes (EASD) and the American Diabetes Association (ADA), with and without diabetic retinopathy, who are receiving metformin therapy. Participants will receive, in addition to metformin, either glucagon-like peptide-1 receptor agonists (GLP-1RAs) or sodium-glucose cotransporter 2 inhibitors (SGLT2 inhibitors).

At treatment initiation (t0) and 12 months after initiation (t1), blood samples, ocular function, peripheral endothelial function, and cardiovascular function will be evaluated.

This study will include 40 participants:

i) 20 participants treated with metformin and GLP-1RAs; ii) 20 participants treated with metformin and SGLT2 inhibitors.

Inclusion Criteria:

1. Individuals aged ≥18 years.
2. Male and/or female patients with T2DM diagnosed according to the criteria established by the EASD and the ADA.
3. Patients receiving only metformin as antidiabetic treatment.
4. Patients who have not previously received SGLT2 inhibitors or GLP-1 receptor agonists.
5. Patients who are able to provide informed consent for participation in the study.

Exclusion Criteria:

1. Patients who are pregnant or breastfeeding.
2. History of multiple severe hypoglycaemic episodes during the past two years.
3. History of ketoacidosis or metabolic acidosis.
4. Active intraocular inflammation in either eye, such as infectious conjunctivitis, keratitis, scleritis, endophthalmitis, or autoimmune uveitis.
5. Patients who have undergone panretinal photocoagulation within the last 6 months.
6. Patients who have received intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy or corticosteroids within the last 6 months.
7. Patients who have undergone cataract surgery or vitrectomy within the last 6 months.

Individuals with type 2 diabetes mellitus (T2DM), diagnosed according to the criteria established by the EASD and the ADA, with and without diabetic retinopathy, who are receiving metformin therapy. Participants will receive, in addition to metformin, either GLP-1 receptor agonists (GLP-1RAs) or sodium-glucose cotransporter 2 inhibitors (SGLT2 inhibitors).