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.
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