Continuous use of computer without rest can cause lethargy and sleep. The muscles controlling the eye lids may fatigue leading to droopy eyes. The symptoms leading to this is called Computer Vision Syndrome or CVS. The main reasons of CVS are Pulsed Electromagnetic Radiation (PEMR) and Artificial light from the Monitor and difficulty in focusing . The Monitor especially the CRT monitor generates PEMR which carries energy radiation. Continuous exposure of eyes to light especially the UV rays from the computer monitor can induce sleep. The retina of eye has photosensitive cells called Rods with Rhodopsin pigment. It undergoes bleaching into Opsin and Retinene when exposed to light. This bleaching reaction elicits nerve impulses which passes into the brain and we see the image by the interpretation of visual signals in the brain.
After the bleaching reaction, resynthesis of Rhodopsin takes place instantly. But if the eye is exposed to light continuously there will not be sufficient time to resynthesize the Rhodopsin. So, as a protective measure, brain induces sleep to close the eyes in order to block light.
Artificial fluorescent light from the monitor is another factor. Artificial fluorescent light is the form of fractioned light which leaves out many segments of the spectral range. Flickering of the screen is also dangerous since the flickering rate is higher than the ‘Flicker-Fusion’ rate of the human eye. CVS is also caused due to bad contrast or excessively or poorly illuminated screen.
The human eye focuses very well on images with a well-defined edge, such as printed material with dark text on a light background. The eyes respond quite differently to electronically generated images shown on a screen. While printed letters and symbols have very distinct edges that are created by layering ink onto paper, images on a Video Display Terminal (VDT) are produced by grouping together small points on the screen known as pixels. The eyes will try to focus on the plane of the computer screen, but cannot maintain that focus for long and will eventually relax to a focal point somewhere behind the screen called the resting point of accommodation (RPA). The eyes constantly switch between focusing on the screen and the RPA, causing fatigue.
Background illumination, posture, positioning of the monitor, ocular conditions like dry eyes and uncorrected refractive errors etc, increases the risk of CVS. Close watching reduces the muscle movements of the eyes and causes strain and fatigue.CVS is more in CRT monitor use but LCD monitor also creates eye strain and fatigue.
If you feel fatigue or monotonous after prolonged use of computer, it is the condition called as Work fatigue. The symptoms of Work fatigue includes, eye strain, dry eyes, head ache etc. The symptoms can be reduced by setting the correct colour contrast of the monitor and giving breaks to computer use, 5-10 minutes break after 1 hour use.
Wide spread overuse of computer and handheld mobile devices is resulting in a harmful and dangerous physical condition on the human body, known as Text Neck.The disorder is associated with chronic headache, pain in the shoulder, neck etc. The frequent forward flexion causes changes in the cervical spine, curve, supporting ligaments, tendons, and musculature, as well as the bony segments, commonly causing postural change.
Pain in the fingers, wrist etc due to the over use of Key board and Mouse. Clinically it is called as Repetitive Strain Injury – a condition caused due to the repetitive task like sitting in the same posture for long time and compression in the wrist and fingers due to over strain in the median nerve.
The human body is not designed to remain in a sedentary position for long periods of time. The highest incidences of back pain are found in workers whose jobs are entirely sedentary or entirely manual like jobs using computers.