Systemic diseases are diseases that involve many organs or the whole body. Many of these diseases also affect the eyes. In fact, an eye exam sometimes leads to the first diagnosis of a systemic disease. The eye is composed of many different types of tissue. This unique feature makes the eye susceptible to a wide variety of diseases, but provides insight into many of body systems. Almost any part of the eye can give important clues to the diagnosis of systemic diseases. Signs of a systemic disease may be evident on the outer surface of the eye, middle of the eye, and at the back of the eye (retina). The optic nerve and eye movements often reflect changes in the central nervous system. This is because a large part of the brain helps provide visual information and controls eye movements. Because the eye structures are uniquely transparent, a doctor can see inside the eye. The eye is the only organ in the body in which a doctor can directly see blood vessels. The health of the blood vessels in the eye often indicates the condition of the blood vessels (arteries and veins) throughout the body. Some of the common diseases that affect the eye are:

Diabetes Mellitus

This is an imbalance in blood glucose (sugar) levels. It can cause severe eye complications, including swelling of the retina (macular edema), abnormal growth of new retinal blood vessels, and bleeding inside the eye. Changes in the blood vessels of the retina or fluctuations in vision sometimes lead to the first diagnosis of diabetes. Diabetic retinal disease is a leading cause of blindness in this country. In addition, people with diabetes develop cataracts earlier than other people. Therefore, it is important for them to have regular eye exams.

Graves Disease

This is a thyroid disorder, most common in women, which can cause a goiter (swelling in the front part of the neck) and protruding eyes. It can cause protruding eyes (proptosis), limitations of eye movement, double vision, and corneal disease. Severe cases may have damage to the optic nerve. Sometimes the eye symptoms in Graves’ disease can appear before other symptoms and signs.

Lupus, Rheumatoid arthritis, and other autoimmune conditions

This is a connective tissue disorder involving mainly the skin, joints, and kidneys. A type of inflammation called uveitis is the most common eye problem caused by sarcoidosis. Uveitis can result in painful and red eyes, blurred vision, and glaucoma. Scleritis, an inflammation of the white part of the eye, can result from systemic lupus erythematosus and rheumatoid arthritis. Both of these conditions also can cause dry eyes.

Hypertension and Atherosclerosis

High blood pressure and atherosclerosis can damage the retinal blood vessels. Usually, this damage does not result in any visual symptoms at first; however, it can eventually lead to more severe complications in the retina as well as in the body. In persons with high blood pressure, the extent of damage in the eye can directly relate to damage that occurs in the kidneys. High blood pressure can be first diagnosed when changes in the blood vessels of the eye are found.

Multiple Sclerosis

This is a disease that damages nerve coverings causing weakness, coordination issues, and speech disturbances. Multiple sclerosis can cause eye movement problems as well as optic nerve disease causing loss of vision. Neurological diseases such as multiple sclerosis may first be suspected when an eye doctor finds changes in eye movement, vision, or the function of the optic nerve.

Shingles (Herpes Zoster)

This infection is produced by the varicella-zoster virus, the same virus that causes chicken pox. After an initial outbreak of chicken pox the virus remains inactive within the nerve cells of the central nervous system. But in some people, the virus will reactivate at another time in their lives. When this occurs the virus travels down long nerve fibers and infects some parts of the body, producing a blistering rash, fever, painful inflammation of the nerve fibers, and a general sluggish feeling. The virus may travel to the head and neck, possibly involving an eye, part of the nose, cheek, and forehead. If the cornea is affected it can decrease corneal sensitivity and can scar the cornea. Doctors can prescribe oral anti-viral medications but if any part of the rash is near the eye,  an appointment with an Ophthalmologist is advised.