Binasal Field Defect in Non-arteritic Anterior Ischemic Optic Neuropathy.

Non-arteritic anterior ischemic optic neuropathy (NAION) is the most common cause of optic neuropathy in older adults and is usually associated with an altitudinal visual field defect. Binasal hemianopia is a rare visual field presentation, and most causes are due to ocular pathology instead of brain pathology. It is an infrequent finding in NAION. We report a rare presentation of binasal hemianopia visual field defect in a patient with NAION. This a case of an elderly lady with underlying uncontrolled type 2 diabetes mellitus, hypertension, and dyslipidemia who presented with a sudden onset of painless blurring of vision in the left eye. She had a similar episode of blurred vision involving the other eye two years ago. Her visual acuity was reduced in both eyes. Humphrey visual field showed a binasal field defect. Fundoscopy showed mild hyperemic optic disc swelling in the left eye and a pale disc in the right eye. The CT scan and MRI were normal. She was co-managed with the medical team to control her systemic risk factors. Although NAION is the most common cause of optic neuropathy in older adults, binasal hemianopia is a rare visual field presentation in NAION. The history and assessment from this case add important information toward diagnosing NAION.