Computer vision syndrome (CVS) is a condition resulting from focusing the eyes on a computer or other display device for protracted, uninterrupted periods of time. Some symptoms of CVS include headaches, blurred vision, neck pain, fatigue, eye strain, dry eyes, irritated eyes, double vision, vertigo/dizziness, polyopia, and difficulty refocusing the eyes.
In CVS, the screen is not considered as a passive object where information is merely displayed. It is an active device that emits radiations towards the user of the computer. For CVS researchers, the screen is emitting phototoxic light whose damaging effect can be reduced by wearing blue light-filtering lenses. An alternative remedy to shielding the retina with specialized spectacles is to follow the 20 20 20 rule. 20 20 20 is an algorithmic formulation of the sequences of action one should follow to avoid CVS: “Every 20 minutes, focus the eyes on an object 20 feet (6 meters) away for 20 seconds”.