Computer Vision Syndrome: Symptoms, Causes and Practical Solutions

For millions of people, the working day now means seven, eight or more hours in front of a monitor, followed by an evening on a phone or tablet. By late afternoon the eyes feel heavy and gritty, the text seems to swim, and a dull headache settles behind the forehead. This cluster of symptoms has a name: computer vision syndrome (CVS), also called digital eye strain.

The good news is that computer vision syndrome does not cause permanent damage to the eyes, and most of its causes are within your control. In this article we look at the symptoms in detail, explain the main causes, and set out practical changes to your workstation, lighting and habits that make a real difference, as well as the signs that mean you should see an eye care professional.

How common is computer vision syndrome?

Studies around the world consistently find that a large proportion of people who use screens for work report at least some symptoms of digital eye strain; in many surveys the figure is well over half. The American Optometric Association (AOA) describes it as one of the most common occupational complaints of the digital era. Symptoms are not limited to office workers: students, gamers, programmers, designers and children doing online schooling are all affected. Risk increases with the number of hours spent on screens without breaks.

Symptoms of computer vision syndrome

The symptoms fall into three broad groups: eye surface symptoms, visual symptoms and body symptoms. Most people experience a mix.

Symptoms usually build during the day, are worst after long, uninterrupted sessions, and improve after rest or sleep. If symptoms are present first thing in the morning, or affect only one eye, another cause is more likely and an examination is advisable.

What causes computer vision syndrome?

Sustained near focusing

To see a screen clearly, the focusing muscle inside the eye (the ciliary muscle) has to contract and stay contracted, a process called accommodation. At the same time, the two eyes turn slightly inward (convergence). Keeping this effort up for hours, at a fixed distance, causes fatigue. After a long session, you may notice that distant objects look blurry for a few moments when you look up; this is the focusing system being slow to relax.

Screen text can also be harder to focus on than print. Characters on a screen are made of pixels with slightly less sharp edges than ink on paper, and contrast may be lower, especially with small fonts or poorly chosen colours.

Reduced and incomplete blinking

Blinking spreads a fresh layer of tears across the front of the eye. When we concentrate on a screen, our blink rate drops considerably, and many blinks are only partial. The tear film then evaporates and breaks up, exposing the surface of the eye and causing dryness, burning and fluctuating blur. This is one of the most important and most underestimated causes of symptoms. Our article on why blinking matters explains this in more detail.

Glare and reflections

Bright windows behind or beside the monitor, overhead lights reflecting from a glossy screen, or a screen much brighter or darker than the room all make the eyes work harder. People often squint or tilt their heads to avoid reflections without realising it, which adds to fatigue and neck strain.

Uncorrected or poorly corrected vision problems

Even a small uncorrected refractive error, such as mild astigmatism or hyperopia, can significantly increase effort at the computer. From the early forties, presbyopia makes near and intermediate focus harder. Many people wear glasses designed for distance or reading at around 40 cm, while a monitor sits at 50 to 70 cm, so neither prescription is ideal. Progressive lens wearers often tilt their heads back to use the lower reading portion, straining the neck. Binocular vision problems, such as convergence insufficiency, can also cause marked discomfort during screen work.

Environmental factors

Air conditioning, heating, low humidity and air blowing from vents or fans all speed up tear evaporation. Contact lens wearers are particularly sensitive to these conditions. If this applies to you, our article on dry eyes in air-conditioned offices offers targeted advice.

Ergonomics: arranging your workstation

A well-arranged workstation reduces both visual effort and physical strain. These are the main principles recommended by eye care and occupational health organisations:

• Distance: place the monitor roughly an arm's length away, typically 50 to 70 cm. If you need to lean forward to read, increase text size rather than moving closer.
• Height: the top of the screen should be at or slightly below eye level, so you look slightly down at the centre of the screen. Looking down reduces the area of exposed eye surface and therefore evaporation.
• Angle: tilt the screen slightly backwards (about 10 to 20 degrees) and keep it straight in front of you, not off to one side.
• Text size and contrast: use comfortable font sizes, dark text on a light background in bright rooms, and adjust zoom freely. High contrast is easier on the eyes than stylish grey-on-grey designs.
• Documents: if you work from paper, use a document holder at the same height and distance as the screen so your eyes do not have to refocus constantly.
• Laptops: for long sessions, use a separate keyboard and raise the laptop on a stand to bring the screen up to the right height.
• Posture: sit back in the chair with feet flat, shoulders relaxed and elbows at roughly a right angle.

Our screen setup tool helps you calculate the ideal distance and height for your monitor size, and our article on the ideal monitor setup covers multiple-monitor arrangements.

Lighting: getting it right

Many offices are lit for paper work, which needs more light than screens. Excess ambient light makes the screen look washed out and creates reflections.

A simple test: the screen should look neither like a light source in the room nor dim and hard to read. Adjust brightness until a white page on screen looks similar to a white sheet of paper on your desk.

Habits that relieve symptoms

1. Take regular breaks. Follow the 20-20-20 rule: every 20 minutes, look at something about 6 metres away for 20 seconds. Add a longer break of several minutes every hour or two.
2. Blink deliberately. During breaks, blink fully and slowly several times, closing the lids completely.
3. Use lubricating drops if needed. Preservative-free artificial tears can relieve dryness. Avoid redness-relieving drops for routine use.
4. Stay hydrated and manage the air. A desk humidifier and moving away from air vents can help.
5. Do short relaxation exercises. Our office programme combines distance focusing, blinking and palming into brief sessions.

Glasses for computer work

If you are over about 40, or if you already wear glasses and still struggle at the computer, ask your optometrist about lenses designed for intermediate distance. Options include single-vision computer glasses set for screen distance, office or occupational progressive lenses that cover desk and screen distance, and adjustments to your current prescription. An anti-reflective coating reduces reflections from the lens surfaces. Lenses that filter blue light have not been shown to reduce eye strain in good-quality trials.

Children and computer vision syndrome

Children may not complain of eye strain directly. Instead, they may rub their eyes, become irritable, avoid tasks, hold devices very close or complain of headaches. The same principles apply: breaks, good lighting, appropriate distance and plenty of outdoor time. Children with symptoms should have an eye examination, as an undetected refractive error or focusing problem is often the cause.

When to see a doctor

Book an eye examination if symptoms persist despite improving your setup and habits, if you have not had an eye test in the last two years, if you are over 40 and struggling with near or intermediate focus, or if you notice double vision, frequent headaches or one eye working harder than the other. An optometrist or ophthalmologist can check for refractive errors, presbyopia, binocular vision disorders and dry eye disease.