Cotton wool spots are specific findings an eye doctor may observe during a retinal examination. These small, fluffy, white patches located on the retina indicate underlying changes in the eye’s delicate structures. Their presence helps eye care professionals assess potential systemic health concerns that might affect the eye.
What Are Cotton Wool Spots?
Cotton wool spots appear as small, fluffy white or yellowish patches on the surface of the retina, often with feathery edges. They are typically less than one-third the size of the optic disc and are usually found near the back of the eye. These spots represent areas where the retinal nerve fiber layer has swollen due to a localized lack of oxygen and nutrients. This swelling occurs because tiny retinal blood vessels become blocked or damaged. The blockage interrupts the normal flow of material within the nerve fibers, leading to an accumulation of debris and swelling.
Underlying Health Conditions
Cotton wool spots are not a disease themselves but a sign of an underlying systemic health issue impacting blood vessels throughout the body. The two most common causes are diabetes, leading to diabetic retinopathy, and high blood pressure, resulting in hypertensive retinopathy.
In diabetic retinopathy, persistently high blood sugar levels damage small retinal blood vessels over time. This damage can cause these vessels to leak or become blocked, leading to a reduced oxygen supply to the retinal tissue and the formation of cotton wool spots. For individuals without a known diabetes diagnosis, cotton wool spots may be an early indicator, with elevated blood sugar found in about 20% of such cases.
Similarly, long-term high blood pressure (hypertension) exerts excessive force against artery walls, including those in the retina. This sustained pressure can damage or block retinal arteries, disrupting blood flow. This causes localized oxygen deprivation and nerve fiber swelling, which manifest as cotton wool spots. In patients with cotton wool spots but no known history of hypertension, an elevated diastolic blood pressure (90 mmHg or higher) is detected in approximately 50% of cases.
Less Common Causes
Less common causes include:
Retinal vein occlusion (a blockage in a retinal vein)
Immune and inflammatory conditions, such as systemic lupus erythematosus
Infectious diseases, including HIV/AIDS
Certain blood disorders
Emboli (small clots that block vessels)
Physical trauma to the eye
Symptoms and Management
Cotton wool spots typically do not cause noticeable symptoms and are often discovered incidentally during a comprehensive dilated eye examination. If a spot is unusually large or located in the central retina, it can potentially interfere with vision, leading to blurriness.
There is no direct treatment for the cotton wool spot itself. Management focuses on identifying and treating the underlying systemic medical condition that caused the spots to form. For instance, controlling blood sugar levels in diabetes or lowering blood pressure in hypertension are primary approaches.
Once the underlying health issue is effectively managed, cotton wool spots often fade and disappear on their own, typically within six to twelve weeks. They may persist longer in diabetic retinopathy. Regular follow-up appointments with an eye doctor and medical specialists are important to monitor retinal health and overall well-being.