Nearsighted Glasses Causing Farsightedness?
March 10, 2010 10:59 AM   Subscribe

Can wearing my glasses prescribed for nearsightedness hurt my close up vision?

I can see things perfectly up close, but I have trouble seeing things far away (nearsightedness). I recently got a prescription for glasses (my first pair ever).

As I was leaving the eye doctor's office, she said offhand something along the lines of "If you only wear them occasionally, you'll probably never need reading glasses". I took this to mean wearing my nearsighted glasses will actually hurt my ability to see things close up.

YANMD, but is there any truth to her statement? Will wearing my nearsighted glasses slowly hurt my ability to see things up close?
posted by chrisalbon to Health & Fitness (11 answers total) 2 users marked this as a favorite
Short answer, nope.
posted by so_ at 11:05 AM on March 10, 2010

posted by The Bridge on the River Kai Ryssdal at 11:07 AM on March 10, 2010

Short answer: No.

Long answer: Being nearsighted actually acts as a buffer against presbyopia (the "arms too short" syndrome). However, when presbyopia does start to kick in, wearing corrective glasses or contact lenses will make close stuff blurrier than it would if you left off your corrective lenses. Solution: take off your glasses to see stuff clearly up close.
A nearsighted (myopic) person can naturally see objects clearly up close, but needs glasses to see things in the distance. The problem with a myopic eye is that it has too much built-in magnifying power, and images that appear in the distance focus inside the eye at a point that lies in front of the retina. Pulling an object closer moves the image further back inside the eye, and eventually the image will focus clearly on the retina. Even after near sighted people become presbyopic (see above) they ALWAYS have the built in ability to see clearly at near. Unfortunately, this may mean holding objects at the end of your nose if you are very nearsighted.

As a myope ages he loses the focusing power of his lens (becomes presbyopic) just like everyone else. However, a myope has a built in ability to see clearly at near as soon as he removes his glasses or contacts. If you wear glasses, have simple nearsightedness (that is, not too much astigmatism), and are over the age of 42, you may have noticed that you need to remove your glasses to see clearly up close. Once you put your glasses back on, your eyes behave just like normal folks (emmetropes), and if you want to read through your glasses, you will need extra magnifying power, just like emmetropes. Since you already wear glasses, now you are going to need a bifocal lens. Having refractive surgery, wearing glasses, or wearing contacts all has the same effect on your eyes, optically speaking. All these methods effectively make you into an emmetrope.
posted by maudlin at 11:24 AM on March 10, 2010

I can think of a few things (which are true) that she may have meant:

1. While you have them on, your near-vision superpowers will be defeated and your ability to focus closely will be no better than other folks around your age with normal sight.

2. Depending on your prescription (if it's just around -1 or -2 spherical and little or no cylindrical) you will probably be fine without bifocals for a long time or forever, since you can simply take them off or look under them for near stuff.
posted by fritley at 11:25 AM on March 10, 2010

If you are younger than 40 or so, they will increase your visual acuity a distance but will not affect your ability to see up close; this is because below that age your eyes can still focus on objects at different distances; as you age, however, your eyes lose this ability as the lens ages and becomes stiff (presbyopia). So with your glasses on you will eventually lose your ability to see up close, but only with your glasses on. As the presbyopia progresses, though, you will eventually need bifocals or something similar. I had a long conversation with the ophthalmologist who did my LASIK about this. Since I was having nearsightedness corrected, I would indeed need reading glasses earlier than if I hadn't had the LASIK, in other words, during the time when a nearsighted person with glasses could simply remove their glass for near vision I would not be able to do that. I am 46 now and don't need reading glasses, but I can tell I will in the next few years. But everyone eventually needs reading glasses or something similar.
posted by TedW at 11:28 AM on March 10, 2010

Response by poster: Thanks all!

For the record I am 26.
posted by chrisalbon at 12:12 PM on March 10, 2010

I JUST had an eye exam, like 15 minutes ago, and I too am nearsighted. And the doctor specifically said that I can wear them for up-close work if I want to (who would WANT to?) but there will be no benefit (no negative impact either). Where I'll see the most benefit (no pun intended) is when driving and the like where I will be looking out over distances.

So no, no danger.
posted by arniec at 12:59 PM on March 10, 2010

There is a plausible argument, based in systems theory, that it should be just the reverse of what your doctor implied.

Your eye has a number of mechanisms that allow it to achieve acuity when you are looking at nearer and farther objects, changing the shape of the lens as was mentioned above, for example.

It makes sense that you, as an uncorrected low myope, would have been pushing these mechanisms toward their limits in favor of seeing objects farther away almost all the time, at the expense of making your close up vision worse than it would have been without such pushing, although your close vision would still probably be at least as good as that of a person with 'perfect' vision uncorrected.

But now with correction, you are able to relax these mechanisms toward their equilibrium in the center, making your close vision better than it was before.

However (as an attempt to save your doctor's observation), the situation could be different for uncorrected high myopes, or myopes whose correction leaves them fairly near-sighted.

Those people's mechanisms could have in essence 'given up' trying to improve far vision, and giving them corrective lenses, especially if those corrective lenses left them slightly undercorrected, as recently was standard practice according to my ophthalmologist, could make their accommodation mechanisms push toward far vision again, causing their close vision to degrade slightly even as their far vision improves.
posted by jamjam at 2:37 PM on March 10, 2010

NO, but age will.
Ask me. I know. Get off my lawn too.
posted by Drasher at 2:43 PM on March 10, 2010

(who would WANT to?)

a potential answer for this: I wear my glasses/contacts constantly, because if I take them off I can't read a book without just about brushing the page with my nose.
posted by jacalata at 5:57 PM on March 10, 2010

I'm nearsighted. My doctor explicitly tells me not to use my glasses when I'm working on close-up work.

My problem was accommodative insufficiency. My eyeball apparently elongated during my early thirties to adapt to all the computer work I was doing, and dropped me from mild farsightedness to mild nearsightedness. If I were to continue to use my nearsighted glasses while working on up-close projects, my eyes would continue to get worse. So I only wear them for walking around or driving.

I think the answer to your question will depend on the exact condition you are having corrected.
posted by pointless_incessant_barking at 7:48 AM on March 11, 2010

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