A 46-year-old woman presents for new onset vision loss in her right eye for the past month. She has no pain or diplopia and feels that her vision has been stable since. Her medical history is unremarkable and felt that she might have had COVID one week before vision loss, but did not test for the virus. Her best corrected visual acuity is 20/60 OD and 20/20 OS with a relative afferent pupil defect OD. Her dilated exam reveals normal optic discs with cupping at 0.6/0.6 OD, OS. Optical coherence tomography (OCT) reveals a normal retinal nerve fiber layer and ganglion cell complex OU. Threshold perimetry is normal in her left eye and there is an inferior arcuate defect in her right eye.
While it is tempting to initially diagnose this as retrobulbar optic neuritis, possibly associated with multiple sclerosis, it would be a superficial assessment. The lack of pain is concerning as the vast majority of patients with retrobulbar demyelinating optic neuritis complain of pain. A painless loss of inferior visual field can often occur from non-arteritic anterior ischemic optic neuropathy, but the normal disc appearance and lack of a disc-at-risk mitigated against this diagnosis.
Upon further discussion, she acknowledged that she felt that she was having trouble with her right contact lens for several months. She acknowledged that her vision loss may have been present for longer than the past month and that she may had just become aware of it. Contrast enhanced magnetic resonance imaging of the brain, orbits, and chiasm revealed a planum sphenoidale meningioma compressing the prechiasmatic portion of the right optic nerve. Subsequent craniotomy with tumor removal was successful, with her visual acuity improving to 20/15 and her visual field loss totally resolved. This was anticipated as her OCT findings were normal, indicating that structurally her visual system was intact though she had functional loss on visual fields.
My first impression was pituitary adenoma