This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Which of the following condition is associated with Macular edema? 
Select and explain. 
A. CRAO, B. Papilledema, C. Diabetes mellitus, D. Age related macular degeneration
C: Diabetes mellitus
Answer: C: Diabetes mellitus 
Explanation: Cystoid macular edema occur following retinal vascular disorders such as diabetic retinopathy caused by diabetes mellitus and central retinal vein occlusion. It can also occur as a post operative complication following cataract extraction and penetrating keratoplasty, following intraocluar inflammation, as a side effect of adrenaline eyedrops and in retinal dystrophies. Must know: Cystoid macular edema: It refers to collection of fluid in the outer plexiform layer (Henle's layer) and inner nuclear layer of the retina centred around the foveola. It occur due to leakage of fluid following breakdown of inner blood retinal barrier. Ophthalmoscopy in this case shows honey comb appearence. Fundus fluorescein angiography shows flower petal appearence. Ref: Comprehensive Ophthalmology By AK Khurana, 4th edn, page 273