People may suffer from blurred vision, red or irritated eyes, double vision, headaches, neck and/or shoulder pain when spending much time with computer or portable electronic devices. This is because characters on computer screens are made up of tiny dots of light called pixels and lack the uniform density and sharply defined borders of text characters printed with link on paper. Constant refocusing caused fatigue of the focusing muscle inside the eye, which is a major component of digital eye strain.