Thresholds and Mechanisms of Human Magnetophosphene Perception Induced by Alternating Magnetic Fields

Abstract

Time-varying Magnetic Fields (MF) are a cornerstone of major modern healthcare technologies and are also a byproduct of our modern environment. Virtually everyone is exposed to power-frequency MF (50/60 Hz), inducing in our body electric fields and currents, potentially modulating brain function. MF-induced electric fields within the central nervous system can generate flickering visual perceptions (magnetophosphenes), which form the basis of international MF exposure guidelines and recommendations protecting workers and the general public. However, magnetophosphene perception thresholds were estimated 40 years ago in a small, unreplicated study with significant uncertainties and leaving open the question of the underlying mechanism. Here, we report magnetophosphene perception in 81 volunteers exposed to MF (eye or occipital exposure) between 0 and 50 mT at frequencies of 20, 50, 60 and 100 Hz. Frequency-dependent threshold were quantified and support an interaction between induced electric fields and retinal rod cells. Beyond fundamental and immediate implications for international guidelines and recommendations, these results have translational potential for the differential diagnosis of retinal disorders.