title: Through a glass darkly.
mesh_terms: D000328:Adult; D000368:Aged; D003027:Cluster Headache / Q000150:complications / Q000503:physiopathology*; D005132:Eye Manifestations; D005137:Eye, Artificial; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013508:Ophthalmologic Surgical Procedures; D010146:Pain; D014653:Vascular Headaches / Q000503:physiopathology*