The light sensitivity of the human visual system depends on the direction of view.

The near-stable North-South orientation of the natural geomagnetic field provides an ideal basis for navigation. Sailors have used it since ancient times, animals for much longer. Various mechanisms have developed for this purpose.

The magnetic field sensitivity of the human visual system shows resonance and compass characteristic.

Orientation in the geomagnetic field is essential for many animal species. As yet, the interaction mechanisms of this weak field with the organisms are understood only incompletely. One mechanism in question is the interaction with the photochemical reaction in the retina.

Periodic inversion of the vertical component of the earth's magnetic field influences fluctuations of visual sensitivity in humans.

According to theoretical considerations, the magnetic field of the earth could influence the first steps of light-induced changes in ocular photopigment, an effect that is thought to underlie the magnetic orientation of some animals. To find out whether man could be influenced in this way, we have tested the effect of an artificial fluctuation in the direction of the earth's magnetic field on oscillations of the visual sensitivity in 27 healthy subjects. The resultant spectra show a significant influence of the field fluctuations, indicating that man is sensitive to changes in the direction of the earth's magnetic field.

Influence of an alternating 3 Hz magnetic field with an induction of 0.1 millitesla on chosen parameters of the human occipital EEG.

In 62 volunteers it was studied, whether an alternating 3 Hz magnetic field (induction 0.1 mT) vertically applied to the head over a period of 20 min causes changes in EEG parameters. The study's design was a random crossover controlled, blind one.