This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glaucoma, Subject name: Ophthalmology
[{'content': 'Marcus Gunn sign is seen in \nSelect and explain. \nA. Retinitis pigmentosa, B. Retinal detachment, C. Diabetic retinopathy, D. Hypeensive retinopathy', 'role': 'user'}, {'content': "Answer: D \nExplanation: Grading of hypeensive retinopathy:Keith and Wegner (1939) have classified hypeensive retinopathy changes into following four grades:_ Grade I: It consists of mild generalized aeriolar attenuation, paicularly of small branches, with broadening of the aeriolar light reflex and vein concealment._ Grade II: It comprises marked generalized narrowing and focal attenuation of aerioles associated with deflection of veins at aeriovenous crossings (Salus' sign)._ Grade III: This consists of Grade II changes plus copper-wiring of aerioles, banking of veins distal to aeriovenous crossings (Bonnetsign), tapering of veins on either side of the crossings (Gunn sign) and right-angle deflection of veins (Salu's sign). Flame-shaped hemorrhages cotton-wool spots and hard exudates are also present._ Grade IV: This consists of all changes of Grade III plus silver-wiring of aerioles and papilloedema.Ref: Khurana; 4th edition; Pg. 258", 'role': 'assistant'}]