Mine I, Shoji T, Kumagai T, et al. - Researchers conducted this cross-sectional study to examine the difference between monocular sensitivities measured with and without background light given to the nontested fellow eye in glaucoma patients using a new perimeter named “imo.” The sample consisted of 51 patients (102 eyes) with open-angle glaucoma who were affected with at least 1 significant point in the central 10 degrees. Using the Humphrey Field Analyzer 24-2 and 10-2 programs, a routine ophthalmic examination and visual field testing were conducted. In the worst eye group of glaucoma patients, monocular sensitivities measured with background light given to the nontested fellow eye were higher than those measured without background light. When assessing the impact of functional impairment in glaucoma patients, monocular mean sensitivity measurements of the worse eyes with fellow eye's background light conditions and their related indices should be carefully considered.