ISCEV standard for clinical visual evoked potentials (2025 update).

Visual evoked potentials (VEPs) are electrophysiologic responses to pattern or flash stimuli, recorded over the occiput. VEPs can provide information regarding the function of the visual system and are valuable in the diagnosis and investigation of optic nerve disease or post-retinal visual pathway dysfunction. The ISCEV VEP Standard specifies stimulus and recording conditions for three basic types of recording: (1) Pattern-reversal VEPs elicited by checkerboard stimuli with large 1° (degree) and small 0.25° check widths. (2) Pattern onset/offset VEPs elicited by checkerboard stimuli with large 1° and small 0.25° check widths. (3) Flash VEPs elicited by a flash which subtends a visual field of at least 20°. The ISCEV VEP Standard protocols are defined for a single recording channel with a midline occipital active electrode. Multi-channel VEPs for evaluation of chiasmal and post-chiasmal lesions, together with protocols specific for pediatric populations, are also described in this document as non-standardized additions. The main changes in the updated ISCEV Standard for clinical VEP include an option to perform a simultaneous pattern electroretinogram (PERG) and pattern-reversal VEP recording, a revised definition of the origin and the analysis of the most prominent VEP components, and more precise descriptions of non-standard multi-channel and pediatric VEP recordings, intended to encourage convergence of widely used non-standard methods. These changes aim to provide a clinically relevant document about current practice which will facilitate good quality recordings and inter-laboratory comparisons.