Cotton wool spots

• DM and HTN are by far the most common cause of cotton-wool spots
• Patients with diabetes mellitus might also harbor other typical retinal findings such as macular edema, retinal exudate, flame or dot/blot hemorrhages, microaneurysms, venous beading or microvascular abnormalities or proliferations
• Patients with systemic hypertension would be expected to demonstrate generalized arteriolar narrowing, arteriolar/venous nicking and, in extreme cases, optic-disk swelling.

Etiologies of Cotton Wool Spots

1) Ischemic

• Ocular ischemic syndrome
• Retinal vascular occlusion
• Anemia
• Increased blood viscocity (e.g. multiple myeloma)

2) Embolic

• Carotid emboli
• Cardiac emboli
• Deep venous emboli
• White blood cell emboli (Purtcher’s Retinopathy)
• Severe chest compression/long bone fractures
• Foreign bodies (IVDA)

3) Infectious

• HIV infection
• Rocky Mountain Spotted Fever
• Cat scratch fever (bartonela henslae)
• Leptospirosis e. Onchocericiases
• Bacteremia
• Fungemic

4) Toxic

• Interferon

5) Radiation

6) Neoplastic

• Lymphoma/Leukemia
• Metastatic carcinoma

7) Collagen Vascular Disease/Immune complex disease

• Systemic lupus erythematosus
• Dermatomyositis
• Polyarteritis nordosa
• Scleroderma
• Giant cell arteritis

8) Tractional

• Epiretinal membrane

9) Traumatic

• Nerve fiber layer laceration

10) Idiopathic