Cotton-wool spots are tiny white areas on the retina, the layer of light-sensing cells lining the back of the eye. They are caused by a lack of blood flow to the small retinal blood vessels. They often disappear without treatment and do not threaten vision. However, they can be an indication of a serious medical condition.
Diabetes is the most common cause of cotton-wool spots. The second most common cause of cotton-wool spots is hypertension (high blood pressure). Other causes of blood vessel disease may cause cotton-wool spots. Your eye doctor may send you to your family doctor or internist to assist in looking for a medical condition that may have caused the cotton-wool spots.