Overview
Cotton wool spots result from a slowing of axoplasmic flow in response to ischaemia. They may result in an retinal nerve fibre layer (RNFL) defect on resolution. There are a wide variety of potential causes of this finding which include the following:
1. Ischaemia: Hypertension, diabetes, ocular ischaemic syndrome, retinal vein occlusion, acute blood loss
2. Inflammatory: systemic lupus erythematosus, giant cell arteritis, polyarteritis nodosa, scleroderma
3. Infectious: HIV retinopathy, Cat scratch disease, bacterial or fungal infection
4. Embolic: Heart disease, deep vein thrombosis, foreign body emboli (eg talc retinopathy), cardiac emboli, carotic emboli
5. Neoplastic: Lymphoma, leukaemia, metastatic disease
6. Treatment induced: Interferon retinopathy, radiation-induced retinopathy
7. Miscellaneous: Papilloedema, eptiretinal membrane, high-altitude retinopathy, trauma
8. Idiopathic
Given the wide range of possible causes, a cotton wool spot in an otherwise healthy person should be thoroughly investigated. Below are links to some of the more common conditions giving rise to cotton wool spots.