A Case of Junctional Scotoma Caused by Idiopathic Optic Chiasmitis at the Macular Fiber Chiasm

Abstract

　A 37-year-old man experienced blurry vision in his left eye. His corrected visual acuity was 1.2 OD and 0.6 OS. The relative afferent pupillary defect was negative. Humphrey visual field test indicated bitemporal hemianopia within 10º of visual field and diminished sensitivity in the central nasal field of the left eye. Brain gadolinium-enhanced magnetic resonance imaging (MRI) revealed an enhanced small lesion slightly to the left posterior part within the center of the optic chiasma. The patientʼs visual acuity recovered to 1.0 without treatment, and his visual field defect disappeared. A repeated brain MRI showed no enhanced lesion in the optic chiasma. We speculate that this patient had inflammation, specifically of the crossed macular fibers and uncrossed fibers towards the left of the chiasma. Consequently, this case supports the anatomical evidence indicating the existence of macular fiber chiasma within the optic chiasm. Moreover, such cases could be misdiagnosed as a nonorganized visual disturbance, especially without appropriate selection of the visual field program.