Cotton wool spots are opaque fluffy white patches on the retina of the eye that are considered an abnormal finding during a funduscopic exam (also called an ophthalmoscopic exam). Cotton wool spots are typically a sign of another disease state, most common of which is diabetic retinopathy. The irregularly shaped white patches are a result of ischemia, or reduced blood flow and oxygen, in the retinal nerve fiber layer, which is located in the distribution of the capillaries of the superficial layer of the retina. These areas with reduced blood flow reflect the obstruction of axoplasmic flow due to mechanical or vascular causes and the consequential accumulation as a result of decreased axonal transport. This reduced axonal transport can then cause swelling or bulging on the surface layer of the retina, increasing the potential for nerve fiber damage.

The presence of cotton wool spots may resolve independently over time, typically in 4-12 weeks, or may depend on the underlying disease causing the condition. Diagnosis and treatment of the underlying disease state may be beneficial in the treatment and management of cotton wool spots.