Hypertension (high blood pressure) is one of the most common medical conditions seen by doctors in Australia and other Western industrialised countries, and causes more deaths than any other cardiovascular risk factor, including smoking and high cholesterol. Although we understand the role of lifestyle factors and have many medications available to treat hypertension, for many patients and doctors it remains frustratingly difficult to control, and in many patients remains undetected. In the American National Health and Nutrition Study (NHANES III) 68.4% of hypertensive patients were aware of their hypertension, 53.6% were being treated, and only 27.4% had control of their hypertension. These figures are worrying because inadequate control of hypertension can lead to “end-organ damage” including kidney disease, peripheral vascular disease, eye disease, stroke and heart attack.
Hypertension is diagnosed when the blood pressure is over 140/90. Some people may be nervous being examined by a doctor and “white coat hypertension” is the phenomenon when your hypertension is only detectable when your doctor checks it. In these cases home monitoring or 24 hour ambulatory monitoring may be required. Malignant hypertension occurs when the blood pressure is over 200/140, and the risk of rapid end-organ damage, including vision loss, makes this a medical emergency.
Although chronic low grade hypertension rarely causes visual loss on its own, it is an important risk factor for a number of conditions that can lead to loss of vision, such as vein occlusion and macro-aneurysm. Malignant hypertension commonly causes visual loss, through direct effects on the retina, choroid or optic nerve.
Patients with hypertension frequently have changes in their retinal blood vessels, which are apparent on careful clinical examination. It’s not uncommon that I discover hypertensive retinal changes on a routine eye examination of someone that hasn’t previously had high blood pressure detected.
Your eyes certainly are a window onto your general health.
Reference: Burt VL et al. “Trends in the prevalence, awareness, treatment and control of hypertension in the adult US population: data from the Health Examination Surveys, 1960–1991”. Hypertension. 1995;26:60.