<s>[INST] A 65-year-old woman presents for a routine eye examination. Her ocular history is significant for bilateral cataracts, which were repaired with cataract surgery in both eyes several years ago. The current corrected visual acuities are 20/20 in the right eye and 20/30 in the left eye. The patient does not currently wear glasses for distance vision. However, she does wear a reading add for near vision.
On further questioning, the patient reveals that she has noticed progressive difficulty judging spatial relationships and navigating stairs over the past several years. She denies any recent trauma or acute changes in vision. Her medical history is significant for hypertension and hyperlipidemia, both of which are well controlled.
On examination, cover testing reveals a small esotropic deviation at near, which increases in size at distance and with lateral gaze. Hertel exophthalmometry readings are within normal limits. The remainder of the examination, including the pupils, motility, and visual fields, is otherwise unremarkable. The patient is referred for an MRI scan of the orbit and a CT scan of the head.
The CT scan reveals a left AION with a hypodense lesion consistent with optic atrophy. What is the characteristic visual field defect associated with this condition?[/INST]