It is hard to deny the prevalence of the internet and technology in our daily lives especially when considering that people in the UK spend an average of roughly 6 hours on an electronic device every single day! Your eyes will inherently have to endure most of the negative effects that are associated with prolonged use of your devices.

Your eyes focus on objects using ciliary muscles that can contract or relax to change the shape of the lens- a transparent, flexible tissue that is found directly behind the pupil. By altering the curvature of the lens, you can refract light by varying amounts depending on the object’s distance.

The culmination of all the effects of prolonged computer use is called Computer-vision-syndrome (CVS) and includes the following symptoms which can affect up to 90% of computer users:

  • Headaches
  • Watery/dry eyes
  • Blurred or double vision (diplopia)
  • Increased sensitivity to light
  • Extra-ocular symptoms such as back or neck pain.

The reason for this is because the focusing systems of the eyes are not well suited for electronically generated characters on your monitor. Letters on a computer screen are not as clear as printed letters due to varying brightness of the pixels and its overall lower resolution. The human eyes find it difficult to sustain focus on a computer screen so end up constantly relaxing and straining to refocus on an imaginary point behind the monitor called the resting point of accommodation (RPA). This constant contraction and relaxation by the ciliary muscles create eye fatigue.

It has also been found that when focused on a video game for example, your blink rate reduces by about half from a normal baseline of 10-15 blinks per minute. The rate of incomplete blinks is also much higher which leads to increased evaporation of moisture from the eye, resulting in dry eyes.

    Other causes include:
  • Poor lighting, either to light/dark or resulting in monitor glare
  • Improper viewing distance
  • Poor seating posture
  • Uncorrected vision problems

Prevention: It is important to wear the correct prescription glasses for you to reduce any unnecessary eye strain. Posture and your workstation arrangement are also particularly important.

  • Optimally, the computer screen should be 15 to 20 degrees below eye level and also be approximately 30 to 50cm away from you.
  • Position the computer screen to avoid glare as much as possible
  • Stick to regular rest breaks. The AOA recommends the 20-20-20 rule where you take a 20s break every 20mins of activity looking at something 10feet away.
  • Finally, a basic tip would be to just remember to blink!


Milad Rouf Final Year Medical Student, Cardiff University.

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