Junctional Scotoma and Patterns of Visual Field Defects Produced by Lesions Involving the Optic Chiasm

Background: Lesions of the optic chiasm (OC) typically produce bitemporal hemianopia (BTH) on visual field (VF) testing, whereas lesions located at the nasal optic nerve-chiasmal (ON-OC) junction have been proposed to produce junctional scotoma (JXS), a central defect in the ipsilateral eye with temporal field loss in the contralateral eye. In this study, we investigated whether the pattern of VF loss in patients with chiasmal compression predicted the appearance of the causative lesion on neuroimaging and described the clinical presentation of these patients with different types of VF defect. Methods: Retrospective chart review of patients seen in tertiary neuro-ophthalmology practice over 6 consecutive years with lesions abutting or displacing the OC was performed. Lesion size and location relative to the OC on neuroimaging was determined and correlated with VF defects as well as optical coherence tomography (OCT) of the peripapillary retinal nerve fiber layer and macular ganglion cell complex (GCC). Results: Fifty-three patients were enrolled. VFs demonstrated JXS (n = 18), BTH (n = 14), monocular VF defect (n = 4), and no VF defect (n = 17); 64.7% of cases with normal VFs had radiologic OC compression. Lesion volume was highest in the JXS group, and these patients also had the poorest presenting visual acuity. All patients with JXS showed involvement of the ON-OC junction; however, not all cases showed compression of the OC from the nasal direction (15 of 18), and 17 of 18 also showed compression of one or both prechiasmatic ONs. Compression of the ON-OC junction was also seen in 79% of BTH, 100% of monocular VF defect, and 59% of no VF defect cases. Fifty percent of patients with normal VFs already had thinning of the GCC on OCT. GCC thinning was most pronounced nasally in the BTH group, but diffuse bilateral thinning was found in 38% of cases compared with 60% of JXS. VFs improved in 6 of 6 patients with BTH but only in 5 of 8 JXS cases after treatment. Conclusions: JXS is more often seen with larger lesions and when there is compression of both the prechiasmatic ON and ON-OC junction. These patients have worse presenting visual acuity and poorer outcomes. Not all patients with radiologic compression had VF defects, although 50% of patients with normal VFs had evidence of compression on the macular GCC analysis, emphasizing the importance of macular OCT in the evaluation of patients with lesions involving the OC.