Baek SU, et al. - In this longitudinal observational study, researchers examined the clinical results of primary open-angle glaucoma (POAG) with an initial single-hemifield defect on visual field (VF) testing and the related risk factors for the involvement of the opposite hemifield during follow-up. The sample consisted of 108 patients (108 POAG eyes) who met the following conditions: single-hemifield defect at initial VF examination and follow-up > 5 years. During the follow-up period, eyes that had undergone noncataract surgery and laser treatment have been excluded. According to the patterns of VF progression, participants were divided into group A (sparing of opposite hemifield) and group B (involvement of opposite hemifield). In total, 63 eyes were classified as group A and 45 as group B. Data reported that the average follow-up period was 7.9 years. According to findings, 41.7% exhibited involvement of the opposite hemifield during the average 8.0-year follow-up in 108 POAG eyes with an initial single-hemifield defect. Findings suggested a significant association of older age and absence of optic disc vertical tilt with a greater likelihood of involvement of the opposite hemifield.