Eye strain is “a feeling of fatigue and soreness that usually happens as a result of extended concentrated activities such as computer work or reading,” says Vicente Diaz, M.D, Yale Medicine ophthalmologist and assistant professor of ophthalmology and visual sciences at Yale School of Medicine. Driving (especially long distances) and classroom work (such as reading a projector or chalkboard) can also result in eye strain, he adds.

Neda Shamie, M.D., LASIK, cataract and corneal surgeon at the Maloney-Shamie Vision Institute in Los Angeles adds that eye strain is a term to describe a set of symptoms, and is not a disease.

During intense concentration, the natural blink rate of the eye slows down, making eyes more dry, uncomfortable and tired. “You may find yourself having a hard time focusing,” she says. “The eyes feel tired and you may feel like you need to close your eyes for comfort.”

Eye strain can also be related to tired eye muscles. When we focus on closer objects like screens, our eye muscles have to work to keep the vision in focus, called accommodation.

“The muscles can go into spasm, much the same way your biceps may spasm after a strenuous exercise, and the eyes find it hard to relax and focus at a distance,” she says.

Digital Eye Strain

Digital eye strain (DES) is the type of eye strain that occurs specifically as a result of digital use, including prolonged computer, phone and tablet use, explains Dr. Shamie. It can also be referred to as computer vision syndrome. The root cause of DES is the combination of looking at a close object that requires a high amount of visual attention for a long period of time, without taking a break. Glare from the screen is a component, too, as it makes the eye uncomfortable.

Additionally, when viewing a screen, letters and numbers are not as precise or sharply defined as on a printed page and the level of contrast of the material to the background is reduced, according to the American Optometric Association. Viewing distances and angles also differ from other tasks, such as reading something close up and straight on, resulting in varying eye focusing and movement requirements that can also strain the visual system.

Due to the increase of screen time and prolonged computer, phone and tablet use, dry eyes are also becoming a permanent problem, increasingly impacting younger patients. A 2018 study in BMJ Open Ophthalmology found that DES may impact up to half of the computer users.

Causes of Eye Strain

While staring at a screen is a major cause of eye strain, it’s not the only one. Other causes include:

• Reading with dim light: Reading with a dim light can cause eye strain due to the struggle of getting your eyes to focus on the page, says Dr. Shamie.
• Focused tasks: Reading in general, for example, “can also cause one to not blink as much,” says Dr. Shamie. “This can then lead to eye strain.”
• Driving long distances or any other task requiring extended time of focus: Long distance drives can often result in eye strain, as eyes often struggle to focus on the horizon, especially after long periods of intense concentration, says Dr. Shamie.
• Having an underlying vision issue or wearing the wrong contact lens or glasses prescription: Wearing the wrong prescription either in contact lenses or glasses forces the eyes to try to focus through that correction, explains Dr. Shamie. “This overexerts the focusing muscles in the eye as well as the muscles that help one squint to bring an image into focus, causing strain and headaches.”
• Stress or fatigue: Stress or fatigue is often the result of long projects, mounting tasks and countless hours working on the computer, staring at screens with little break, says Dr. Shamie, “which in turn leads to eye strain caused by dry eyes.”