Optic nerve sheath meningioma
C. Another MRI scan of the orbit
The initial presentation of unilateral optic disc edema with intact vision raises an interesting differential diagnosis, including incipient nonarteritic anterior ischemic optic neuropathy (NAION), unilateral papilledema, compressive optic neuropathy, and optic perineuritis. Risk factor modification (choice A) would not be correct because it is the next step in the management of NAION, for which hypertension, hyperlipidemia, diabetes, and obstructive sleep apnea are commonly found modifiable vascular risk factors.1 Visual acuity can be normal in the setting of disc edema in incipient NAION; however, the duration of optic swelling would have been shorter, and NAION would not have caused gaze-evoked amaurosis.1,2 Nonarteritic anterior ischemic optic neuropathy most commonly causes an inferior altitudinal defect, whereas our patient had peripheral field loss in the right eye. A lumbar puncture (choice B) is not the next step, but it would be used to obtain the opening pressure to diagnose papilledema, which can also cause visually asymptomatic disc edema. However, papilledema causes transient visual obscurations and not gaze-evoked amaurosis.