Many patients do not complain of any symptoms and the raised blood pressure is discovered during unrelated examination or during screening programmes. Diagnosis may only be found when a complication occurs such as a heart attack or stroke. Headaches occasionally occur but shortness of breath and angina is rare. The clinical signs depend on the elevation of the blood pressure. In mild hypertension the only signs are raised blood pressure on measurement. In moderate to severe high blood pressure secondary changes may be seen in the vessels on the retina of the eyes and early signs of heart damage.