Prevent Digital Eye Strain - No more headaches/migraines, blurred vision, difficulty focussing or strained eyes (Digital Eye Strain) from using your digital screens. These 'HEAVY DUTY' lens block 98.5% of all HEV blue-light on 400-520nm spectrum and 100% from 400nm, emitted from all digital screens. This is perfect for heavy duty users, offering maximum protection for those staring at screens for long hours, such as Coders, Gamers, Office workers and those with serious sleep issues. Sleep Better - It is not just your eyes, but also your brain which can be adversely affected by digital screens. HEV blue light can affect your circadian rhythms, tricking your brain into thinking it’s the middle of the day and preventing you getting a good night’s sleep.