CRP and anterior ischemic optic neuropathy: A-RION, anterior radiation-induced optic neuropathy; P-RION, posterior radiation-induced optic neuropathy; AION, anterior ischemic optic neuropathy; MRI-DTPA, magnetic resonance imaging - gadolinium DTPA; FA, fluorescein angiography; OCTA, optic coherence tomography angiography; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; CSF, cerebrospinal fluid; CGCA, giant cell arteritis