Computer use is often characterised by viewing a monitor or other display up close and focusing intently on it. After extended use you tend to not blink as fast. This causes increased strain on your eyes and vision as well as dehydrating your eye balls.
Then it all goes downhill from there and you are very uncomfortably suffering from eye strain, headaches and the myriad of other Computer Vision Syndrome symptoms.
An overuse syndrome, studies show that the vast majority of computer users suffer from Computer Vision Syndrome. However it is relatively simple to diagnose. It is not that difficult to treat Computer Vision Syndrome. And with some good ergonomic practices it is possible to prevent Computer Vision Syndrome altogether.

