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.