- The study eye shows definite retinal thickening due to a CRVO based on clinical examination involving the center of the macula that is not refractory to further therapy as based on the investigator s clinical judgment. CRVO is defined as an eye that had retinal hemorrhage or other biomicroscopic evidence of RVO (e.g., telangiectatic capillary bed) and a dilated (or previously dilated) venous system in at least three quadrants of the retina drained by the affected vein.