I've heard it said very often: Using a computer/smartphone can make you nearsighted.
Is it true? Is there good research on the topic?
Yes, it can, just as much as reading or any other activity where you're looking at something close to your eyes.
Doing a substantial amount of near work on a regular basis can increase the risk for myopia. Myopia is associated with greater time spent reading and doing near work, better reading test scores, more years of education, occupations that require a great deal of near work, and greater academic ability
Personal computers are possibly one of the most empowering tool humanity has ever created. They're tools of communication, creativity, and they can be shaped by the user.
But, of course they "computers" come with various negative effects. One negative effect is affecting your eyesight.
Computer users (including me) have reported many eyesight problems like blurred vision, redness in the eyes, fatigue, eye strain, dry eyes, irritated eyes, double vision, vertigo/dizziness, polyopia, and difficulty refocusing the eyes resulting from computer display.
The medical community had to create a term for all those eyesight problems, which is:
It is defined by the American Optometric Association as:
the complex of eye and vision problems related to near work which are experienced during, or related to, computer use.
Somewhere between 50% and 90% of the people who spend three hours or more a day at a computer as reported by the National Institute of Occupational Safety and Health.
Also, a total of 795 students, aged between 18 and 25 years, from five universities in Malaysia filled a questionnaire survey study regarding the duration of daily continuous use of computer, symptoms of CVS,...
Ninety percent of university students in Malaysia experienced symptoms related to CVS, which was seen more often in those who used computer for more than 2 hours continuously per day.
It has been reported by the National Center for Biotechnology Information that children get affected by it. The study reported that:
Children can experience many of the same symptoms related to computer use as by adults. Extensive viewing of the computer screen can lead to eye discomfort, fatigue, blurred vision and headaches, dry eyes and other symptoms of eyestrain.
It has been mentioned also here:
Currently it seems that there is no clinical evidence linking computer use results to permanent vision problems. So, it is unlikely that the use of computers causes permanent changes or damage to the eyes or visual system.
World Health Organization. Provisional statements of WHO working group on occupational health aspects in the use of visual display units. VDT News, 3(1):13,1986.
Mutti DO, Zadnik K. Is computer use a risk factor for myopia? J Am Optom Assoc, 67(9):521-30, 1996.
A study compared computer and hardcopy conditions with regard to blurred vision during a task.
30 normal subjects read identical text (same size, contrast, viewing angle, luminance) aloud either from a desktop computer screen or a printed hardcopy page at a viewing distance of 50 cm for 20 minutes.
Immediately following completion of the reading task, subjects completed a written questionnaire asking about their level of ocular discomfort during the task.
Significant differences in median symptom scores were reported with regard to blurred vision during the task (t = 147.0; p = 0.03) and the mean symptom score (t = 102.5; p = 0.04).
Symptom scores mean: observations on discrepancies when defining symptoms using words and numbers.
Symptoms following sustained computer use were significantly worse than those reported after hard copy fixation under similar viewing conditions.
That most important factor is the angle of gaze at the computer monitor.
Twenty-eight people participated in an experiment and measured:
The distance from the eye to the computers' monitor (A)
the computers' monitor height (B)
and visual axis height (C)
D was defined as B (the computers' monitor height) - C (visual axis height)
Angles of gaze to the computer monitor, could be found by, angle=tan(-1)(D/ A).
Then they divided angles into two groups:
Group 1: participants with angles of gaze ranging from 0 degrees to 13.9 degrees.
Group 2: participants gazing at angles larger than 14 degrees.
Statistical analysis of the evaluated variables was made. The results:
Computer users in both groups used more tear supplements (as part of the syndrome) than expected. This association was statistically significant (p<0.10). Participants in Group 1 reported more pain than participants in Group 2. Associations between the CVS and other personal or ergonomic variables were not statistically significant.
Clinical studies of myopic progression and transient myopia among VDT users are considered, as is television viewing as a risk factor for juvenile myopia.
Dr. Maria Liu, head of the new Myopia Control Clinic at UC Berkeley’s School of Optometry said:
There are a number of factors involved in the increase of myopia, but I have no doubt that changes in lifestyle over the past several decades that include more time spent indoors and the early use of handheld computers play a big role.
The problem with smartphones and iPads is that kids often hold them closer to their eyes than they would a book, and they can become totally absorbed for hours at a time. The working distance for handheld devices is much closer than it is for laptops and TV.
Many eye doctors who specialize in children’s vision say sustained computer use puts kids at higher risk for childhood myopia (nearsightedness). They point out that, though myopia affects approximately 25% of the U.S. population, nearly 50% of adult computer users with a college education are nearsighted. Computer use, especially among youngsters whose eyes are still changing, may be the reason for this disparity.
Research seems to support this theory. A study of 253 children between the ages of 6 and 10 at the University of California at Berkeley School of Optometry found a strong correlation between the amount of time young children spend on the computer and their development of nearsightedness.
Which really means that there is absence of evidence, but not necessarily evidence of absence. It is still a theory.
A very important report (referenced, clear, and simple) by American Optometric Association.
Information for cause, diagnosis and the treatment for CVS by American Optometric Association.
YouTube video about How to Protect your Eyes from Computer Vision Syndrome.