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Cotton wool spots are yellow or white flocculent artifacts that arise on the surface of the retina, or the part of the eye that can detect, process, and sum light information for the brain. Retinal spots form after blood flow to the retina is obstructed. These entities typically do not damage vision and are often naturally reabsorbed by the eye. There are many diseases and infections that can lead to the production of these spots, but the most common causes of this condition are diabetes and high blood pressure. The presence of these spots is an indication of the advanced progression of these diseases and is a sign that these diseases need to be more aggressively treated in order to control their impact.
The retina is composed of layers of cells that collect light information and transfer that information via ganglion cells back to the brain. Cotton wool spots are composed of cytoplasmic material that has leaked from ganglion cells onto the surface of the retina. It is believed that this material leaks from the ganglion cells after a disease or infection causes the delicate blood flow to the retina to be blocked. As the cytoplasmic material oozes from the damaged ganglion cells, it takes on the fluffy, fleecy appearance of cotton or wool that has given this condition its name.
Typically, cotton wool spots do not diminish vision and do not require direct treatment. In fact, most patients do not even know they have these objects in their eyes until a funduscopic exam is performed to evaluate the health of the eyes. These retinal artifacts, however, are a sign of disease or infection that has severely impaired the blood flow to the retina. If the disease or infection that has damaged the retinal blood supply and caused these spots is not identified and treated, then more severe eye problems could develop.
The most common causes of these retinal artifacts are the diseases diabetes and hypertension, or high blood pressure. When eight or more cotton wool spots are observed in an eye, the potential impact of diabetes or hypertension is considered severe, and immediate action to control these medical problems is required. If the diseases are not better managed, they will have a detrimental physiological impact on the retina. The existence of cotton wool spots in a patient infected with the human immunodeficiency virus is an indication that the severity of the infection is substantial. Other medical conditions and infections that can produce these cotton-like artifacts include severe anemia, connective tissue diseases, and leptospirosis.