Studies have indicated 70 percent to 90 percent of people who use computers extensively, whether for work or play, have one or more symptoms of computer vision syndrome. The effects of prolonged computer use are not just vision-related. Complaints include neurological symptoms like chronic headaches and musculoskeletal problems like neck and back pain.
Unfortunately I've started to experience this over the past three months. Continual fatigue, frequent headaches, inability to focus on screens for long periods of time, higher sensitivity to brightness...it sucks. For a while my routine had me in front of a screen for more than twelve hours per day.
I'm not sure what to do besides be aware of it and start taking small steps to reduce screen time. This means more frequent breaks at work to walk a lap in the hallway, or moving back to paper books, or dimming the brightness on all my devices as low as comfortably possible. It's starting to help, but I'm still far ahead of the three-hour-per-day range of comfort.