A 29-year-old obese woman presented to the emergency room with horizontal binocular diplopia, new headaches and transient visual obscurations. Examination revealed an elevated blood pressure of 146/101, visual acuity of 20/20 in both eyes, a right abduction deficit (75% of normal), moderate bilateral optic disc edema and enlarged blind spots in both eyes on visual field testing. Magnetic resonance imaging (MRI) and magnetic resonance venography (MRV) showed signs of raised intracranial pressure and lumbar puncture in left lateral decubitus position demonstrated an opening pressure of 38 cm of water with normal cerebrospinal fluid contents.
She was diagnosed with idiopathic intracranial hypertension (IIH) and was started on acetazolamide 500 mg BID and followed on a monthly basis. She also started on ramipril for hypertension. Acetazolamide was increased to 750 mg BID at the one-month follow-up and 1g BID at the two-month follow-up due to increasing papilledema at which time she reported resolution of the diplopia. A few days after her two-month follow-up, she developed sudden loss of vision in the superior part of the visual field in her right eye. At her three-month follow-up, she had a new right RAPD and a superior altitudinal visual field defect on Humphrey 24-2 SITA-Fast visual field testing .
She was diagnosed with a right anterior ischemic optic neuropathy. There was a reduction in the optic disc edema in both eyes at that time, with mild temporal pallor evident in the right more than the left eye. Her symptoms of headache and transient visual obscurations also resolved. The right superior visual field defect persisted at subsequent follow-ups.
In summary, NAION should be considered as a cause of vision loss in patients with papilledema especially when the vision change is sudden. This must be differentiated from visual field defects from worsening papilledema, which may require surgical intervention
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