We have a running joke in my household. My husband and I make a good pair because he can see well at a distance, but not close, while I’m the opposite—I can still read without glasses, but everything distant is quite fuzzy. We could still function even if we both lost our glasses as long as we’re together! But it may not be an accident that we ended up like this.
Use it or lose it?
I always presumed this had something to do with the “use it or lose it” theory. My husband’s job as a teacher involved keeping a close eye on a lot of squirmy middle-graders, both at the front and (especially!) at the back of the class. He was constantly refocusing on different distances but didn’t spend as much time examining things up close.
In contrast, my job as a pharmacist required me to spend a lot of time working on a computer, entering and checking prescriptions, and looking at bottles of pills up close to make sure they were the right ones. As it happens, my favourite hobbies are knitting and reading, both of which require close-up focus, so I’ve spent a lot of my life focussing close rather than far.
New results from an ongoing study of young students in China support my observation, especially in children aged 6 to 8. In 2019, 5.7% of six-year-olds were near-sighted, requiring glasses to see clearly distance clearly, but in 2020, after an extended period of lockdown, that number had jumped to 20%... 1 in 5 now needed glasses for distance. The difference for 7-year-olds was 16.2% vs 26.2%, and for 8-year-olds it was 27.7% vs 37.2%.
They note that, during their lockdown, children were not allowed outside often. They also spent time looking at computers for home schooling rather than looking around a classroom as they normally would in school.
Here’s the science…
Dr. Caroline Klaver, ophthalmologist and researcher at Erasmus Medical Canter in Rotterdam, explains a likely mechanism for the development of myopia (near-sightedness). It takes energy to focus the eye on something close. When we require the eye to do this for long periods of time without breaks, the physical shape of the eye can change, becoming elongated (front to back) to make the task of focussing easier. Having a genetic predisposition for this also makes it more likely that a permanent change will occur. If you are near-sighted, your children are more likely to be too.
So, developing near-sightedness is believed to be a combination of genetics and environment… “nature plus nurture”. The researchers believed the unusual increase in myopia in 2020 was a combination of more screen time for schooling and less time being outdoors, another well-known risk factor for developing near-sightedness, as you usually focus on more distant objects when outside.
She also explains that, although we tend to blame screen time, your eyes don’t know what you’re looking at. Looking at anything closely for long periods of time (like me with my knitting and books) has the same effect.
However, the effect appears to be greatest in children when the eye is growing and developing. According to this recent study, 6 to 8-year-olds were most affected, with a gradually decreasing impact in older children even though they spent more time home-schooling on a computer than the younger children did.
Better to prevent…
Although many of us think of myopia as a relatively minor inconvenience, requiring glasses or contacts to correct vision, it also increases risk of eye problems in later life, Klaver explains. The physical lengthening of the eye front to back that happens in myopia means there is more area at the back of they eye for the retina (the light sensing structure at the back of the eye) to cover. This can lead to increased risk of glaucoma or retinal detachment and vision loss. Developing myopia at a younger age can further increase risk.
To reduce risk, it is recommended to give the eyes a break every 20 minutes when doing close work by looking off into the distance (for example, out the window) for at least 20 seconds. Playing outside for 2 hours a day is also recognized as reducing risk of becoming near-sighted.
What about presbyopia (far-sightedness)?
Almost everyone loses their ability to see up close as they age but some lose it sooner and more severely than others. Most sources say there is no way to prevent presbyopia, the inability to focus on close objects that makes us need reading glasses as we age.
However, there doesn’t appear to be much actual research into whether this loss of close vision can be prevented. A close focus close requires tiny muscles in the eye to change the shape of the eye’s lens, focussing your vision on what you’re looking at. Eye specialists tell us that the lens becomes stiffer with age and eventually can no longer change shape enough to focus closely, and that’s when we start needing reading glasses. Another theory says that loss of function of the tiny ciliary muscles or changes in the structures in front or back of the lens may also contribute to the problem. However, exactly why this happens with age is not understood.
Can everyday activities help?
I can’t help wondering if what you do every day makes a difference. I lost the ability to overpower my distance contact lenses enough to read easily some years ago, but I can still read without any lens. My adjustment for this was to switch to wearing one contact lens—one eye to see distance and the other to read. My optometrist told me not everyone can do this, but my brain only took a couple of days to adjust. I had previously tried the “bifocal” contacts but couldn’t see clearly close or far with them… my brain just couldn’t sort out the near and far mixed focus the lenses provided, although many people can. Aren’t our brains interesting!
So, I’ve been wondering if there’s a logical reason why I can still manage without reading glasses while my hubby is constantly looking for his (who knows where they all disappear to…). On average, people first report presbyopia symptoms between age 42 and 44 and develop complete lack of accommodation (the ability to change the eye’s focus) by age 50 to 55. Experts universally agree there’s nothing you can do to reverse presbyopia once you have it, however there is some anecdotal suggestion that a prevention program promoting general eye health with the addition of eye exercises, alternating focus near and far, might help prevent it. We know that exercise helps to maintain function in essentially every other part of the body… it would make sense that it could help the eye’s lens too.
Unfortunately, there isn’t good science to say this works, but it certainly wouldn’t do any harm to make a habit of changing your focus periodically when doing close work. Those with occupations requiring extensive use of near vision are reported to notice symptoms earlier more often than others the same age. So, this doesn’t fit with my theory of using my close vision more than my hubby. But perhaps I was changing my focus at work more than I realized as I checked for customers at the counter between prescriptions. My habit of knitting while watching TV over the years may have worked in my favour too, causing me to change my focus often as I checked for dropped stitches.
So, while it may be too late for many of us, we can encourage our children and grandchildren to spend time outdoors and to take breaks from close work to change focus.
References:
Presbyopia—Eyewiki
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