Proposed Mechanism for Central Retinal Artery Occlusion Following Neurointervention Other Than Thromboembolism: Iodine Contrast

Objective: Nonionic contrast media to lower osmolality are widely used in most cerebral angiography. But, there is no ideal contrast media near to blood which has similar viscosity and osmolality. The authors proposed mechanism by contrast media itself as the possible cause of rare central retinal artery occlusion. Material and Methods: The first case is the 47-year-old female complained decreased visual acuity immediately after transfemoral cerebral angiography (TFCA). Diffusion magnetic resonance (MR) showed no evidence of intracranial lesion. Some branches of central retinal artery (CRA) were obstructed and retinal edema was found on fluorescence fundus photography. The second case is about the 67-year-old male who developed the central retinal artery obstruction (CRAO) 1hour after coil embolization on unruptured cerebral aneurysm. Results: The current available nonionic contrast media have various range of osmolality, in those the iopamidiol has the lowest osmolality but it is far from that of human blood. The mechanisms of CRAO the authors suggest are as follows: (1) periarterial edema from hyperosmolality and induced inflammation, (2) thrombogenic effect from higher viscosity, and (3) decreased blood flow and barrier aggravating ischemia. Conclusion: The authors suggest that angiography operating setting (e.g., tube voltage selection) should be optimized in circumstances with lower osmolar and viscous contrast media.