Patients with high blood pressure (hypertension) and chronic kidney disease are at an increased risk of developing heart disease and strokes. Part of this risk is due to changes in the structure and function of the blood vessels throughout the body. It is thought that reducing high blood pressure and treating chronic kidney disease improves the structure and function of blood vessels but information on this is limited. Optical coherence tomography (OCT) is a method of looking at the blood vessels at the back of the eye. It is a simple, quick and non-invasive test that you may have previously had during a visit to the optician. The purpose of the study is to ascertain whether OCT is able to detect changes in the eye's blood vessels in patients with hypertension and chronic kidney disease compared to healthy individuals and also to see if any differences seen improve with treatment.

This project is an exploratory study, using enhanced depth imaging with the new SPECTRALIS OCT, designed to examine choroidal and microvascular retinal structure in patients with hypertension, chronic kidney disease (CKD), and in age and sex matched healthy controls. The study is non-invasive and takes only a few seconds to acquire these complex images. The Centre, where the images will be captured and where image analysis systems are located, is on the Royal Infirmary of Edinburgh (RIE) site close to the RIE outpatient clinics, making recruitment easy.

Inclusion Criteria:

• Male or female
• Age 18-80
• Body mass index ≤35
• For those with hypertension: BP ≥140/90 or on treatment for hypertension
• For those with CKD: CKD as defined by the Kidney Diseases Quality Initiative guidelines

Exclusion Criteria:

• Subject is below the age of legal consent, or is mentally or legally incapacitated
• The subject has donated blood (450 ml) within the last 4 weeks
• Past or present drug or alcohol abuse including intravenous drug abuse at any time
• Participation in another clinical trial within 1 month
• Considered to be at high risk of HIV or hepatitis B
• Patients with known eye disease, or previous eye surgery, or refractive error greater than +/- 6 dioptres.

Healthy volunteers will be recruited from a research database. CKD and patients with hypertension will be recruited from these respective clinics in secondary care.