Cotton Wool Spots

What are cotton wool spots?

Cotton wool spots are puffy, white areas on the retinas at the back of your eyes. Cotton wool spots aren’t something you can feel or see yourself, although they may cause a temporary blind spot (scotoma). The only way your healthcare provider can see them is by using the proper tools.

Cotton wool spots get their name because they look like absorbent cotton. This material is better known under the term “cotton wool” in the United Kingdom. In the United States, absorbent cotton is commonly called “cotton balls” (or “cotton bolls,” for the boll part of the cotton plant, where the fibers come from).

What are the most common causes of cotton wool spots?

Cotton wool spots happen when there’s swelling, damage or other changes to the retina tissue that lines the back of your eye. The affected areas look puffy and lighter-colored than the surrounding tissue. They look like tufts of cotton when viewed directly by an ophthalmoscope.

Many conditions can cause this kind of change in retinal tissue. They tend to fall under the following categories:

• Circulatory. Lack of blood flow (ischemia) can cause cotton wool spots. This can happen because of diseases like Type 2 diabetes and high blood pressure (hypertension), or when circulating blood clots or other items get stuck in blood vessels (that’s called an embolism). High blood pressure and diabetes are the most common causes of cotton wool spots.
• Immune and inflammatory. These happen when your immune system or inflammatory responses don’t work correctly, damaging your body instead of helping it.
• Infections: This is when microscopic invaders like viruses, bacteria, fungi or parasites attack part of your body. They can cause cotton wool spots if they attack your retinal tissue. Human immunodeficiency virus (HIV) and Rocky Mountain spotted fever are two examples.
• Cancer. Blood cancers like leukemia and lymphoma can cause cotton wool spots. Cancer that spreads (metastasizes) from elsewhere in the body can also be a cause.
• Bleeding disorder. Having too little hemoglobin (anemia) or too few platelets (thrombocytopenia) can cause cotton wool spots. Having blood that’s prone to clotting can also cause them.
• Intracranial hypertension. A thin layer of cerebrospinal fluid (CSF) surrounds and cushions your brain and spinal cord. But if too much CSF builds up, it can press on your brain. Your eyes are vulnerable to damage from the increased pressure and shifting of brain tissue.
• Medication. Certain medications, especially ones meant to boost immune function (like interferon), can cause cotton wool spots.
• Injuries and event-related damage. Injuries can damage blood vessels in and around your retinas and cause cotton wool spots. They can also happen under certain circumstances, like traveling to high altitudes.

In some cases, there’s no detectable cause of cotton wool spots. When that happens, the cause is idiopathic (unknown).

How are cotton wool spots treated?

Medical professionals can look at your retinas using a handheld instrument called an ophthalmoscope. This tool allows a provider to look at the retinal tissue at the back of your eye. Providers commonly use it during a physical or eye exam. Cotton wool spots are also visible during a slit lamp exam, which lets a provider look at the back of your eye with special lighting and magnification.

There’s no way to treat cotton wool spots directly. Treating whatever’s causing them is the only way to resolve them. When the underlying causes are treatable and reversible, cotton wool spots are usually a short-term issue. They usually go away within six to 12 weeks.

Because so many different conditions and events can cause them, the treatments vary widely. Your healthcare provider is the best source of information regarding treatment options and which are most likely to help you.

What are the possible complications or risks of not treating cotton wool spots?

Cotton wool spots are a sign of conditions that affect your retinas. Without treatment, these conditions can further damage your retinas and cause them to become thicker or thinner in ways they shouldn’t. When those changes are severe enough, they can disrupt your vision.

But the effects of many of these conditions don’t stop there. Many of them have effects throughout your body, including effects that can be severe. Your healthcare provider is the best person to tell you the possible complications in your situation and what you can do to prevent or minimize them.

Can cotton wool spots be prevented?

Many causes of cotton wool spots are preventable, but they happen unpredictably. Some things you can do to lower your risk of developing cotton wool spots include:

• See a primary care provider for a yearly checkup (these can detect problems that can cause cotton wool spots long before you have symptoms you can feel or see)
• Manage what you eat to ensure you get proper nutrition
• Reach and maintain a weight that’s healthy for you
• Stay physically active
• Don’t ignore infections
• Wear safety equipment to protect your head and eyes
• Manage chronic health conditions