Q. Mercury is a poisonous liquid. So doctors prefer to keep the thermometer on the fore head. Thermometers are made up of hard glass casings inside which the mercury is kept. There is no data to show that working before a computer for more than 7 hours is harmful to the eyes. Depending on each person, the contrast of the screen has to be adjusted to give minimum strain on the eyes.
Some people do use extra screens on their computer monitors to lower the glare from the terminal.
Eyes blink automatically to adjust the fluid pressure in and around the eye. Eye is the most important of all the sensory organs human being have. You should not watch a TV screen from very close. It is bad for your eyes. Bright glare and moving pictures will make your eyes tired.