This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Retina, Subject name: Ophthalmology
The clinical findings differentiating ophthalmic aery occlusion from central Retinal aery occlusion is 
Select and explain. 
A. Sudden painless loss of vision, B. Box carring of vessels, C. Area of retinal whitening, D. Absence of cherry red spot
D: Absence of cherry red spot
Answer: D: Absence of cherry red spot 
Explanation: Within a few hours of CRAO the retina loses its transparency, becoming opaque and milky-white, especially in the neighbourhood of the disc and macula. At the fovea centralis, where the retina is extremely thin, the red reflex from the choroid is visible and appears as a round cherry-red spot, presenting a strong contrast to the cloudy white background. As choroid derives its blood supply from the ophthalmic aery, in ophthalmic aery occlusion even choroidal circulation is affected and hence a cherry-red spot is not clearly visible