September 20, 2006
The Eye in Common Diseases
I don't know if the eye is truly the window to the soul, but it is certainly a window to general health. Because the inside of the eye must be transparent, it is the only place you can observe veins, arteries and nerves directly. Over the years I have detected many illnesses which manifest themselves in the eye and in visual symptoms. Here are some key areas in the eye that I observe:
The retina: Diabetes is in fact one of the leading causes of blindness in the U.S. When present in the back of the eye (in the nerve layer called the retina), it is called retinopathy. Early stages of diabetic retinopathy are rarely noticed by the patient. I will see small clusters of blood, called microaneurisms, leaking from capillaries. In addition, there may be some larger hemorrhages in the surrounding tissues. Later on in the disease, the leaking vessels will lead to rapid growth of weak capillaries, creating a vicious cycle of hemorrhages and possibly retinal detachment.
High blood pressure and high cholesterol in early stages are quite detectable in the eye. There is a certain appearance to the crossing points of veins and arteries on the retina that indicates chronic hypertension. High cholesterol will show up as high reflectivity in the small arteries of the eye. In more advanced cases, I will see hemorrhaging, straightening of arteries or tortuosity (looping back and forth) of the veins. Both of these diseases can cause blockage of the arteries or veins, leading to serious vision loss.
Many forms of cancer (colon, lung and melanoma for example) and leukemia may be indicated when changes in pigmentation in the deeper layers of the retina are seen. Over 50 percent of patients with AIDS show blood vessel blockage and whitened areas called cotton wool spots; viral and parasitic infections are extremely common as well.
The optic nerve: Many neurological diseases can be seen in the optic nerve. It enters the eye within the retina, and is clearly visible as what is called the optic disc. This is the closest cranial nerve to the brain. Frequently, tissue changes relating to disease can be observed. Brain tumors, either benign or malignant, may show a swelling of the optic disc. Patients with MS commonly suffer from inflammation of the optic nerve (optic neuritis); this can occur at a very early point in the disease, or much later. Patients will complain of intermittent blurring, usually in one eye.
The iris: This muscle tissue is what gives us our eye color. It forms the pupil, though which light passes to focus on the retina. The pupil size should vary with exposure to different illumination. If it does not, or if one pupil suddenly is a different size than the other, stroke or neurological disorder should definitely be considered.
Multiple episodes of inflammation of the iris (iritis) is a likely symptom of a number of diseases including arthritis, lupus, ankylosing spondylitis (degenerative disease of the spine, sarcoidosis (inflammation and deposits in a number of tissues of the body), tuberculosis, syphilis, Crohn's Disease (a GI inflammatory disease) or colitis . . . quite a list! You should suspect iritis with sudden blur and extreme light sensitivity.
Visual symptoms to be aware of: Tumors will often manifest in early visual symptoms. Sudden blur or sudden onset of double vision should always be regarded as potentially serious, and should never, ever be ignored. Uncontrolled diabetics will often experience daily fluctuations in their eyeglass prescriptions. Darkening of vision, either in one eye or both, may indicate decreased blood flow from cholesterol buildup or other blockage.
Looking at this partial list should be enough to convince you that an eye exam is far more than what you do just when you want new glasses!