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M. Takimoto, K. Yanashima, K. Magatani; Quadrantic Checkerboard Pattern Reversal VEFs: Case of Homonymous Hemianopsia . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2713.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To examine the quadrantic areas of the visual field separately by visual evoked magnetic fields (VEFs) requires considerable time. In addition, it is difficult to decide the position and size of the absolute equivalent current dipoles for the four quadrants because, with the conventional pattern reversal stimulus, we must record the individual responses from each quadrant. To record VEFs from all quadrants simultaneously, we have developed a pattern stimulus which has a different stimulus trigger and interval for each quadrant. The aim of the present study was to evaluate the VEFs elicited by this stimulus. Methods: VEFs were recorded from normal subjects without any ocular diseases except refractive errors, and from patients with homonymous hemianopsia with the whole-head MEG system (VectorviewTM). Refractive errors were corrected with a nonmagnetic frame and optical lenses. The checkerboard pattern reversal stimulation was composed of the four quadrants, and each was stimulated with a different stimulus trigger and interval. VEFs were recorded simultaneously from the four quadrants. The responses around 100 ms after the stimulus trigger (M100) were estimated. Results: In controls, M100 responses were recorded from the primary visual cortex for each quadrant. In patients with homonymous hemianopsia, the M100 responses of the right upper and lower visual field stimulation were present in the primary visual cortex, but the responses of the left visual field were not recorded. Conclusions: With quadrantic pattern stimulation, VEFs can be recorded simultaneously for each quadrant. The quadrantic pattern stimulation can be used to detect visual field defects objectively in a short time.
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