A Matter of Facts About Eyes

You use your eyes every waking moment, so here are some things worth knowing about them, and a few simple habits that keep them comfortable.

Did you know…

1. You blink many times a minute. Each blink spreads a thin film of tears across the front of your eye, which keeps it moist and comfortable.
2. You blink less at a screen. When you concentrate on a phone, a computer or a book, you tend to blink less, which is one reason eyes can feel dry or tired at the end of a long day.
3. The cornea does most of the focusing. The clear front window of the eye does about two-thirds of its focusing. The lens behind the pupil then changes shape to focus on things near and far.
4. Your pupil changes size with the light. The iris, the coloured part of the eye, opens in dim light and closes in bright light, so the pupil gets bigger or smaller.
5. Your retina works like the sensor in a camera. It lines the back of the eye and turns light into signals for the brain. Its small centre, the macula, gives you the sharp central vision you use for reading and seeing detail.
6. Your brain does a lot of the seeing. The optic nerve carries signals from each eye to the brain, which puts them together into one picture.
7. You have a blind spot, and you never notice it. Where the optic nerve joins the back of each eye there are no light-sensing cells. Your two eyes cover for each other, and your brain fills in the gap.
8. Two eyes give you depth. Working together as a team (this is called binocular vision), your eyes let you judge how near or far things are.
9. Eye colour comes from the iris. Some people are born with a different colour in each eye. This is called heterochromia.
10. The lens inside your eye becomes less flexible from about our forties. That is why reading gets harder, and it is a normal part of getting older. Reading glasses, bifocals and multifocals all help. Read more on our vision over 40 page.

Looking after yours

• Give your eyes a break from screens and close work. Every 20 minutes, look at something about 6 metres (20 feet) away for 20 seconds.
• Blink often when you are at a screen.
• Have your eyes tested every year. At an eye test your optometrist checks how well you see, how your eyes work together and how healthy your eyes are.

Book an eye test and tell us about your day: your work, your screens, your driving and your hobbies.