Background, focus, and key pointsA 51-year-old woman presented with a pressure-like headache behind her right eye and horizontal diplopia. On exam, she was unable to abduct or adduct the right eye but had intact vertical eye movements. Her deficits could not be overcome using the oculocephalic reflex. Imaging initially was interpreted as optic neuritis, but on careful review with radiology, a diffuse enhancing hyperintense signal within the orbital apex confirmed an orbital infiltrate. The focus of this case study is to review the localization approach for diplopia and build a differential diagnosis for orbital processes. Another key point is the importance of relying on the physical exam as the guide to a patient’s management rather than imaging findings, which can often be misleading.