You blink far less when you look at a screen. That is why your eyes burn by evening

When you concentrate on a screen, you blink much less. In one well-known study, people's blink rate fell from around 18 times a minute in normal conversation to fewer than four while they worked at a computer. Other studies since have found similar drops, and that many of the blinks we do make on screens are only partial, not closing the eye fully.

With fewer blinks, the tear film dries out and breaks up. The result, at the end of a long day of laptop work, phone scrolling and TV, is the familiar set of symptoms: dry, gritty or burning eyes, redness, blurred vision that clears when you blink, headaches, and eyes that water too much as they try to catch up. Doctors call it digital eye strain, and it is now one of the commonest eye complaints among office workers and students.

Easy on the eyes - Follow the 20-20-20 rule: every 20 minutes, look at something 20 feet away for 20 seconds. - Make a point of blinking fully and slowly a few times whenever you look away from the screen. - Keep the screen at arm's length and just below eye level, and reduce glare from windows and lights. - An AC or fan blowing at your face dries your eyes faster. Point it elsewhere. - If your eyes stay red, painful or blurry, or you haven't had your eyes tested in two years, see an eye doctor. Sometimes the answer is simply the right glasses.

Where this comes from - Patel S et al. Effect of visual display unit use on blink rate and tear stability. Optometry and Vision Science, 1991. - Sheppard AL, Wolffsohn JS. Digital eye strain: prevalence, measurement and amelioration. BMJ Open Ophthalmology, 2018.