What finding is most characteristic of central retinal artery occlusion?

The finding most characteristic of central retinal artery occlusion is a pale fundus with a cherry red spot. In this condition, there is an obstruction of blood flow through the central retinal artery, leading to ischemia (lack of oxygen) in the surrounding retinal tissue, which appears pale or white because of the lack of blood supply.

The cherry red spot occurs at the fovea, which is the area in the center of the retina that is thinner and has a higher concentration of photoreceptors. Since the foveal area is devoid of the underlying retinal pigment epithelium and choroidal blood supply remains intact, there appears a contrasting red spot against the pale surrounding retina. This classic clinical finding is crucial for diagnosing central retinal artery occlusion and differentiating it from other retinal pathologies.

Other findings like optic disc edema, retinal edema with cotton wool spots, or flame-shaped retinal hemorrhages may suggest different retinal conditions such as retinal vein occlusion or other forms of retinopathy, but they are not hallmark signs of central retinal artery occlusion.