Many people who regularly use computers suffer from eye strain and fatigue. Looking at a monitor for a long time can strain your eyes or can make any other problems you are having with your eyes seem more apparent. There is also research to show that late-night exposure to bright lights can affect sleep quality. This can be mitigated by reducing blue-light exposure.
We recommend four free software solutions below. All but f.lux are released under an open source license. f.lux is freeware.