Eye Strain in the Digital Age - Causes, Symptoms, and Evidence-Based Solutions

Eye Strain Is Really Muscle Fatigue

Eight hours or more in front of a PC, a smartphone during the commute, video on a tablet after getting home. Modern eyes are under a load they have never faced before. In a survey conducted by Japan's Ministry of Health, Labour and Welfare in 2008, about 70% of workers reported physical fatigue or symptoms from information equipment work on the job (the term used until 2019 was VDT work), and the most common symptom was "tired or painful eyes."

The main cause of eye strain is not blue light but "overtension of the ciliary muscle." The ciliary muscle adjusts the thickness of the lens to bring things into focus, and it contracts when you look at something close. Look at a PC or a smartphone for hours and the ciliary muscle stays contracted and can no longer relax, which brings on deep aching behind the eyes, blurred vision, and headaches. It is the same state as holding your arm bent for hours on end.

Three Symptom Groups from Information Equipment Work

Eye Symptoms

Tired eyes, dryness, redness, blurred vision, difficulty focusing, sensitivity to brightness. These arise from ciliary muscle fatigue and dry eye acting together. From your 40s onward in particular, the lens loses elasticity (the start of presbyopia), which increases the burden on the ciliary muscle even further.

Physical Symptoms

Stiff shoulders, neck pain, headaches, lower back pain. The posture you adopt to look at a screen easily becomes "forward head posture," with the head jutting out ahead of the body, which places excessive load on the neck and shoulder muscles. The head weighs about 5 kg, but tilting it forward just 15 degrees increases the load on the neck to roughly 12 kg.

Mental Symptoms

Irritability, anxiety, reduced concentration, poor sleep. Eye fatigue disturbs the balance of the autonomic nervous system and produces overactivity of the sympathetic branch. Smartphone use before bed lowers sleep quality not only because of blue light but also because of the autonomic disruption that comes with tired eyes.

How Dry Eye Develops

Blinking Less

Normally a person blinks about 15 to 20 times a minute. When you are concentrating on a screen, however, that drops to 5 to 7 times a minute. Blinking is what spreads tears evenly across the surface of the eye, so when it becomes less frequent the tear film breaks up and the cornea dries out.

Lower Tear Quality

Tears have a three-layer structure: an oil layer, a water layer, and a mucin layer. The oil layer, secreted by the meibomian glands (the sebaceous glands along the edge of the eyelid), keeps tears from evaporating. When long hours of screen work or leftover eye makeup clogs the meibomian glands, the oil layer runs short and tears evaporate more easily. In an air-conditioned office, humidity can fall to 30 to 40%, which accelerates that evaporation further.

The Effect of Blue Light - Overrated Versus Actual

What Blue Light Is

Blue light is visible light with a wavelength of 380 to 500 nm, and sunlight contains it as well. The amount of blue light emitted by PC and smartphone screens is only a few dozenths of what is in sunlight. One hour outdoors on a clear day exposes you to far more blue light than eight hours in front of a PC screen.

The Effect on the Retina Is Limited

Animal experiments have shown that high-intensity blue light damages retinal cells, but those experiments used intensities far removed from ordinary conditions of digital device use. The American Academy of Ophthalmology (AAO) has stated its view that the scientific basis for blue light from digital devices causing eye disease is insufficient.

Do Blue Light Blocking Glasses Work?

Multiple randomized controlled trials have produced negative results on the effect of blue light blocking glasses against eye strain. A 2023 Cochrane review concluded that blue light filtering lenses may not reduce symptoms of eye strain during computer use (with the caveat that follow-up was short term and the certainty of the evidence is low). Rather than investing in blue light blocking glasses, practicing the 20-20-20 rule described below is far more effective. If you want to be able to tell for yourself what works and what does not, an evidence-based guide to eye health is a good way to build a foundation of knowledge.

The 20-20-20 Rule - The Simplest Effective Measure

The 20-20-20 rule means that every 20 minutes you look at something at least 20 feet (about 6 meters) away for 20 seconds. Looking into the distance lets the ciliary muscle relax and releases the tension of focus adjustment. Setting a reminder every 20 minutes with a timer app is the practical way to do it.

On top of the 20 seconds of distance viewing, deliberately blinking about 10 times also helps prevent dry eye. Find methods that are easy to fit into daily life, such as looking at the view outside the window or at the wall on the far side of the office.

Adjust Your Environment to Reduce the Load on Your Eyes

Screen Settings

Set screen brightness to roughly the same level as the ambient light around you. A screen much brighter than its surroundings tires the eyes, and one that is too dark makes you squint to read the text. Set text size so that it reads comfortably from arm's length (about 60 cm). Position the monitor so that the top of the screen is at or slightly below eye level, and the exposed surface of the eye shrinks, which holds down tear evaporation.

Adjusting the Room

Angle the air conditioner vents so the airflow does not blow directly at your eyes. Keeping indoor humidity at 40 to 60% with a humidifier suppresses tear evaporation. Even just putting a small USB humidifier on your desk improves the humidity around your eyes.

When to See an Ophthalmologist

If you have any of the following symptoms, this may not be simple eye strain but an eye disease, so you should see an ophthalmologist: a sudden drop in visual acuity, part of your visual field going missing, rainbow-like rings around lights (halos), a sudden increase in floaters, or eye pain that does not improve with rest. From your 40s onward the risk of glaucoma rises, so making an annual eye examination a habit is recommended.