On retinal examination of a diabetic patient, cotton wool spots are noted. What is the cause of cotton wool spots seen in this case?

Cotton wool spot is a small focus of superficial retinal opacification that develops after focal retinal ischemia with secondary axoplasmic damming. They are located in the nerve fiber layer of the retina in the posterior pole, but are not seen in the periphery. Diabetic retinopathy is the most common cause of cotton wool spots. Conditions associated with retinal edema are: Diabetic retinopathy Hypeension Retinal vein occlusion Retinal aery occlusion Retinal macroaneurysms Retinal vascular malformations Other forms of retinal vasculopathy Hyperviscosity Papilloedema Neuroretinitis Ocular trauma Age related macular degeneration Ref: The Wills Eye Hospital: Atlas of Clinical Ophthalmology edited by William Tasman, M.D 2nd edn page 210, The Retina in Systemic Disease: A Color Manual of Ophthalmoscopy By Homayoun Tabandeh, M.D page 40