I purchased three different blue light blocking glasses from three different suppliers. I am in behavioral sleep therapy from a local hospital provider because my circadian rhythm became disrupted following unplanned quadruple heart bypass surgery! The quality and performance of this pair are excellent compared to the other two. One of the others is actually designed to protect eyes from industrial laser beams and is thus much darker. The this pair is the least expansive and adequate, however both go the other glasses are too dark to use if I need to go to the bathroom in the middle of the night. This best pair costs the most, however performs very well. I had some difficulty finding OTG Blue Blockers that fit over my large glasses, tried a few others that were just too small. If these ones were a little less expensive I would probably buy two more pair, but as my income is fixed (I am retired) I will be very happy with the one pair.