William Shakespeare once said, “The eyes are the window to your soul.” This is poetic and philosophical, but can the eyes be more practical and be a window on the heart as well? A cataract is a common eye disorder that occurs as people get older. Are cataracts associated with heart disease or a higher risk of dying? Could a cataract be a new risk factor for cardiac disease?
A cataract is a clouding of the lens in the eye. The eye uses a natural lens to alter the light coming into the eye to help us see. With aging, the proteins in the lens start to break down, causing vision to become cloudy, like looking through a foggy or dusty windshield. Aging is the most the common cause of a cataract. People over 60 years old may start to have clouding, although severe symptoms may not develop for years. Aside from older age, other risk factors for cataracts include diabetes, smoking, heavy alcohol use, hypertension, working in direct sunlight, certain medications such as corticosteroids and a family history of cataract. Once symptoms become severe, the treatment is surgery. An eye doctor can replace the cloudy lens with a clear artificial lens and restore sight. Cataracts are quite common and a major cause of visual impairment worldwide. Approximately 90% of Americans over age 65 will develop cataracts and 4 million cataract surgeries are performed each year in the United States.
Are cataracts associated with heart disease or a higher risk of dying? Many studies have been done to try to answer these questions, with conflicting results. More recent data points to an association between these processes. The Nurses Health Study followed 60,000 women, aged 45 to 63, for 10 years. The study found that cataract extraction significantly increased the risk of dying from heart disease. A recently published study looked at 15,000 Americans over the age of 40 with a follow up of 10 years. This study found significant associations with cataract surgery and the risk of dying. Patients who have had cataract surgery had a 13% higher risk of dying from any cause and a 36% higher risk of dying from heart disease. Lastly, a study from Israel showed that cardiovascular disease was significantly more prevalent in cataract patients undergoing surgery.
How are cataracts and heart disease connected? There are several possible unifying mechanisms. Cataracts and heart artery disease share some common risk factors, such as older age, hypertension, diabetes and smoking. Oxidative stress causes damage and break down of the proteins in the lens. Of course, stress also causes plaque and blockage in the heart arteries. Another mechanism involves proteins in the lens called crystallins. These proteins are present throughout the body and help regulate the body’s response to inflammation and ischemia (low blood flow). The break down of these proteins in the eye and throughout the body may a more widespread systemic disorder rather than a localized problem involving just the eye. Lastly, both cataract and heart patients are more prone to depression.
Does this mean that cataracts are a new risk factor for cardiac disease? Not necessarily. Both cataracts and heart disease are common problems and both occur as we get older. It is possible that the both conditions are a consequence of ageing or some other systemic process and not causally related. The research doesn’t show that cataracts cause heart disease. Even so, it seems prudent for patients with cataracts to keep an eye out for symptoms of heart disease and see their doctor quickly if symptoms develop.
