After a long summer break, kids are heading back to school and turning their attention to learning. But more time in the classroom means more time in front of screens.
The article “5 ways to protect from short-sightedness in children” doesn’t mention the real reason short-sightedness progresses in children who spend a lot of time in front of screens. When the eye focuses at a far away object, it is relaxed. When focusing closeup, the eye must accommodate, which means the ciliary muscles contract, releasing tension on ligaments that hold the lens. So, the lens then springs back to a thicker, more rounded shape that increases its refractive power.
However, the eye tries to adapt to a long-term situation, meaning that it tries to remain in a relaxed position. So if someone spends a lot of time reading closeup, it will change the shape of the eye or the lens so that the ciliary muscles can be relaxed while reading closeup. That’s called myopia.
Sometimes, it’s genetic, when you see very small children wearing eyeglasses. It obviously didn’t come from closeup reading. However, to prevent the adaptation of the eye to be relaxed when reading closeup, wearing reading glasses will enable the eye to focus far away (on infinity) and be able to read close up.
Notice that people who wear glasses all the time tend to keep getting stronger and stronger prescriptions for their eyeglasses if they spend a lot of time reading, because the eye wants to continually adapt to make it relax when reading. The way to thwart that is to not wear glasses while reading, or if vision is too far gone, use glasses with an older, less powerful, prescription, so the ciliary muscles don’t have to contract as much.
Believe it or not, I figured this out in elementary school, when I observed kids who wore eyeglasses coming back after summer vacation with ever stronger eyeglasses. I was myopic and refused to get eyeglasses. Fortunately, I was always assigned a seat in the first row in school because I was very short. And when eye test time came, I would just memorize the bottom line of the eye chart that was always hung in front of the room. In middle school, I couldn’t cheat because the teacher cleverly put the eye chart in the back of the room.
So, I was given a prescription to visit an ophthalmologist who told me I would have to wear glasses the rest of my life. Hogwash, I thought. I never had his prescription filled and that worked until I was 18 years old and had to pass the State’s driving test. My vision was about 20/40 or 20/50 as I remember. Since I wanted to drive, I got the eyeglasses but only wore them while driving or when going to the movies. And that continued, my vision not changing for the next 62 years, when I had to have cataract surgery at the age of 80.
And cataract surgery, at least in the U.S., seems to have a silly vision goal for most people who have it done! I had the power of the replacement plastic lenses selected so that my left eye can see clearly between 12 and 18 inches, and my right eye can see clearly from 18 inches to 39 inches. That’s called monovision. However, my perception with both eyes open is that everything is clear from 12 inches to 39 inches and I’m unaware of my eyes switching which one takes precedence. It turns out that the image my brain creates comes from the eye that makes things clearer, and the other eye adds three dimensionality. And blurry vision doesn’t actually become noticeable until much further away. At home I can see everything clearly. And it’s nice not to have to wear glasses at home, unless I’m watching a movie on TV.
Almost all people, if they get the monovision solution for cataract replacement lenses, seem to get them to correct for one eye to focus clearly for intermediate distance and the other eye for far distance. That means they must wear glasses for the 95% of the time they are not looking at Mars or driving or going to the movies. And without glasses they can see clearly from about 5 feet to infinity. Everything close up is blurry without glasses. That makes no sense to me.