Eye strain and symptoms caused by computer use is called Computer Vision Syndrome - a term used to describe a range of eye strain and pain.

With the use of digital devices so commonplace for both adults and children, it's important to ensure that the way they're used is optimised to 

How Do Computers Affect Vision?

As you work at a computer, your eyes have to focus and refocus constantly.  Your eye muscles need to make very precise movements to allow you to read and work smoothly. They may look up and down from the screen to other objects in the distance, and need to refocus closer to see your keyboard or other objects. All of this requires a great deal of effort from your eye muscles.

Additionally, screens can vary greatly in quality, contrast, refresh rate, and glare.

If you have an existing eyesight problem, working on a computer for a prolonged period of time can exacerbate it. So, it's important to wear glasses if you have them. If you need glasses but don't have them, or if you wear the wrong prescription for computer use, you might find you could be working much better after a proper assessment.

Computer related eyestrain can occur at any time, and at any age, but it may also be exacerbated by age-related changes and may get worse with time, if not well managed. Around the age of 40, your ability to change focus from near to far objects will start to worsen, as well as your ability to see things up close (known as presbyopia). This can worsen issues relating to Computer Vision Syndrome.