Magneto- and electrophosphene thresholds in the retina: a dosimetry modeling study

Objective.Sensations of flickering light produced by time-varying magnetic fields or electric currents are called magneto- or electrophosphenes. Phosphene thresholds have been used in international guidelines and standards as an estimate of the thresholds of exposure that produce effects in the central nervous system (CNS). However, the estimated threshold values have a large range of uncertainty.Approach.Phosphene thresholds were approximated by simulating five phosphene threshold experiments. Retinal electric fields and currents induced by electric and magnetic stimulation were calculated using the finite element method and 14 anatomically realistic computational models of human heads.Main results.The radial component of retinal current density was determined to be in the range of 6.0-20.6 mA m^-2. This study produces more accurate estimates for threshold current density in the retina using detailed anatomical models and the estimates had a reduced range of uncertainty compared to earlier studies.Significance.The results are useful for studying the mechanisms of retinal phosphenes and for the development of exposure limits for the CNS.