Temporal light modulation from LED lighting and seizure risk: A focused review of visible flicker, invisible modulation, and evidence gaps

Critically assess whether light emitting diode (LED) lighting temporal light modulation (TLM) is linked to seizure risk while distinguishing established evidence on visible flicker in photosensitive epilepsy from weaker evidence on prolonged exposure to invisible or supra-critical flicker fusion (CFF) modulation. The review also lists desired data: modulation depth at 100/120 Hz, waveform and driver parameters, neurological symptoms, and ethically possible seizure-incidence observations under measured lighting. The narrative focused review used a structured search of recent literature and targeted inclusion of foundational and immediately relevant findings. Intermittent photic stimulation and visible flicker, prolonged exposure to invisible or supra-CFF TLM, temporal light artifacts during eye movements, modulation depth and waveform, and practical study designs for neurological and seizure data were categorized. Visible flicker in photosensitive epilepsy, notably in the 3-65 Hz range, with maximal sensitivity at 15-25 Hz, is the strongest evidence. Susceptible people may have seizures after intense stroboscopic exposure, but this does not prove that LED illumination with high-frequency imperceptible modulation causes seizures. Even without seeing the flicker, continuous exposure to 100 Hz lights can cause headaches, eyestrain, and increased visual-cortex activity, according to foundational research. Phantom array effects reveal that supra-CFF modulation may cause visual discomfort during saccades. Direct evidence relating typical LED modulation depth to seizures is missing. Evidence suggests caution, not causality. Thus, the paper's goals are to define what is known and what should not be overinterpreted and to suggest ways to gather more data. Because seizures are rare and safety-critical, double-masked studies should initially prioritize more common and lower-risk outcomes like headache, eyestrain, visual discomfort, task performance, and cortical activation in relation to modulation depth, while seizure incidence should be examined through carefully monitored secondary endpoints or prospective surveillance under measured lighting conditions.