This prospective clinical study will involve the non-invasive assessment of retinal vessels using OCTA (Cirrus OCT 6000 AngioPlex) and scanning laser Doppler flowmetry (SLDF) in patients with cardiovascular disease and healthy individuals. The study will be conducted at the Clinical Research Centre (CRC), Department of Nephrology and Hypertension at the University of Erlangen-Nuremberg.

Each patient (32 patients) and healthy individual (32 healthy individuals) undergoes one study visit. After providing informed consent, each patient and healthy individual receives an assessment of their retinal vessels using OCTA and SLDF. In the sub-study of 10 patients with cardiovascular disease, the reliability of the OCTA measurements will be determined. Each patient will receive three study visits (with an OCTA and SLDF assessment on each occasion) on three different days.

Inclusion Criteria for patients with cardiovascular disease:

• cardiovascular disease defined as one or more of the following: arterial hypertension, type 2 diabetes mellitus, chronic kidney disease, heart failure

Inclusion Criteria for healthy individuals:

• BMI 18-29.9 kg/m2
• Non-smoker
• Good general health, as determined by study personnel based on assessments of previous visits, including anamnesis, vital signs, physical examination and clinical laboratory parameters.

Exclusion criteria for patients with cardiovascular disease:

• Active ophthalmological (retinal) disease resulting in impaired visual assessment of retinal vessels (e.g. glaucoma, cataracts, retinal oedema).

Exclusion criteria for healthy individuals:

• Active ophthalmological (retinal) disease with reduced visual assessment of retinal vessels (e.g. glaucoma, cataracts, retinal oedema).
• clinically relevant deviation in physical examination, vital signs, or laboratory parameters (based on the physician's clinical judgement).
• a clinically relevant history of cardiovascular disease or any other previously known cardiovascular disease
• History of clinically relevant neurological, gastrointestinal, renal, hepatic, psychological, pulmonary, metabolic, endocrine or other diseases
• office blood pressure above or equal to 140/90 mmHg
• Office heart rate outside of the following range: 50-99 bpm
• regular intake of any medication for the treatment of cardiovascular diseases (e.g. antihypertensive or antidiabetic medication) within one month before study inclusion
• alcohol or drug abuse