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This abstract is assigned to session OB Free papers: Strabismus / Neuro-ophthalmology

Title	Right hemisphere dominance in multi-channel VEP recording.
Abstract Nr.	330

Purpose	Multi-channel visual evoked potentials (VEP) are often recorded as a diagnostic tool to demonstrate visual field defects in patients who are not able to perform perimetry. Previous studies have shown a right hemisphere dominance for sinusoidal gratings. Does this hemispheric asymmetry exist for standard pattern-reversal VEP recording?
Methods	Retrospective analysis of VEP recordings of 37 children (0 to 10 years of age) and 11 adults (18 to 75 years of age) with no known visual field defects. Three active channels were used according to the ISCEV guidelines: two lateral electrodes were placed at O1 and O2 and a third midline active electrode at Oz. All three active electrodes were referenced to a common electrode Fz. A standard pattern-reversal VEP was performed. Results of the 60’ element size are reported.
Results	In children, no hemispheric preference was observed for latency. With regard to amplitude, however, a significant right hemispheric predominance was observed ( 72% of right eyes and 71% of left eyes). Mean interhemispheric difference was 4.4µV for right eyes and 3.6µV for left eyes. Mean hemispheric difference was comparable in both eyes. In adults, a similar hemispheric asymmetry was observed: 91% of right eyes and 70% of left eyes showed a right hemisphere dominance for amplitude. However, the effect was much smaller than in children (1.4µV for the right eyes and 1.5µV for left eyes).
Conclusion	Caution is needed when interpreting amplitude data in multi-channel pattern reversal VEPs because of right hemisphere dominance.

Author 1

Last name	COECKELBERGH
Initials	T
Department	Universitair Ziekenhuis Antwerpen / Universiteit Antwerpen
City	Edegem