Fundoscopy image of the retina of the eye showing arteriovenous nicking (in blood vessels down centre right). This is where a retinal venule is compressed by a retinal arteriole that has become stiffened by disease. The walls of the arteriole have also thickened, given them the appearance of a copper wire. Both of these changes are caused by high blood pressure (hypertension) and are a sign that the patient has chronic systemic hypertension.