The human circadian rythm is entrained by the sun. Using VR glasses for playing games or watching movies, the user is completely shielded from environmental lighting. There is neither an influence of natural daylight on circadian rhythm nor from artificial environmental lighting. The only light source which contributes to the circadian rhythm is the display of the VR headset. Since VR glasses are mostly used in the evening or during the night when melatonin secretion begins, phase delays of sleeping rhythms and bodily functions are expected. To quantify melanopic illuminance, the measured illuminance is weighted with the melanopic sensitivity function. The received melanopic lux correlate with the intensity of melatonin suppression. We measured and calculated values for each of the different display color and demo scenes used in VR glasses. The demo scenes are screenshots from different situations in commonly known games that can be played in virtual reality. For a white background e.g., we measured an illuminance (at eye level) of 90 lx, a melanopic action factor of 0,96 and 105,6 "melanopic lux". From this we assume that melatonin will be significantly suppressed in the evening using VR glasses. In a future study we will investigat the expected effects.