Low endogenous recanalization in embolic central retinal artery occlusion--the retrobulbar "spot sign"

Central retinal artery occlusion (CRAO) is most often indirectly diagnosed by lack of retinal perfusion. Direct embolus characterization may help to understand the natural course and low response to treatment. In a previous study we identified a hyperechoic signal within the optic nerve and in the central retinal artery ("spot sign").

In this study we performed a follow-up investigation in 7 patients with CRAO and positive spot sign indicating the embolic cause of the occlusion after a median interval of 17 months (range 11-38 months) using a battery of tests (ocular color-coded sonography, optic coherence tomography [OCT], fundoscopy, amongst others).

The spot sign persisted in all patients, none had high-grade internal carotid artery stenosis, stroke or transient ischemic attacks. Four patients were completely blind, 3 patients were able to recognize hand movements. OCT demonstrated retinal atrophy, and fundoscopy revealed only minimal arterial perfusion.

The hyperechoic spot sign may be an important predictive prognostic marker for persistent loss of vision. Its persistence may indicate calcified or cholesterol emboli and may explain the low therapeutic success rate to thrombolysis. Further studies on their origin and significance in atherosclerotic disease are warranted.