Okay, not many people wear glasses in my family so we aren’t used to them. This is probably an easy question for those who wear glasses. My sister and I were debating about whether an uncle is nearsighted or farsighted because we can’t remember.
When you stand in front of him and look at him, his eyes look bigger when he wears his glasses. Kind of like this guy, but not as pronounced.
Is he nearsighted or farsighted?
Does he wear the glasses all the time or just for reading/looking at things within arms distance? If he uses them all the time for viewing the world around him (driving, etc.) then he is probably near sighted. If he just uses them to look at things close up then he would be farsighted.
Uh… Hm… I don’t quite remember, but I think he wears them pretty much all the time.
We’re having the debate because my sister’s MIL is nearsighted and when she wears her glasses her eyes look smaller than they are in real life, and I’m quite sure Uncle Dude’s eyes look bigger.
And we’re both too stubborn to call him long distance to ask something so silly.
Eyeglasses for those that need assistance for near vision (that is, a farsighted person) have converging lenses, which will bend the light so as to magnify the eyes. The opposite, for nearsighted people, will have a diverging lens, which will bend the light so as to minify the eyes.
Yeehaw! That means I win! He’s probably farsighted!
:: Spikes football, does endzone dance ::
Thanks!
An example for the opposite effect: I am 9.5 dioptries nearsighted (i.e. without glasses I can only see clearly to a distance of 4 inches) and my SDMB picture gallery photo shows how much smaller my eyes look behind glasses.
If he’s over a certain age (i.e., 40), he could just be presbyopic and not hyperopic (far-sighted). Everybody who has normal vision becomes presbyopic at around age 40.
Mops
Probably a typo, but if not, the word is “diopters.”
Thanks, you are right; I neglected to look up the unit name in English.
Ok, I always get this twisted around.
I can read books and the computer fine. I need glasses to read road signs. Anything more than 6 feet away requires glasses.
So, I’m nearsighted? If my prescription is strong, I get tiny, beady eyes?
Sarah Palin’s eyes are magnified in photos. So she’s badly farsighted? She needs glasses to read a book. But, should be able to read a road sign 15 feet away?
Have I got that right?
Yes. If you’re nearsighted you can’t see things (clearly) far away.
Yes, you’re nearsighted. You have the vision (uncorrected) to see near. Near sight. Get it? People who are far sighted can sight (see) far without their glasses.
I don’t know Palin’s eye sitch, but probably. It’s complicated as you age because most people nearing 40 start to develop presbyopia, which is like far sightedness but specifically due to age. It’s the one that makes you need reading glasses that you didn’t need when you were young. But it doesn’t give you the ability to see far if you’re already nearsighted, either. So older adults who were nearsighted while young can be, effectively, both near *and *far sighted when presbyopia sets in - and that’s when they need bifocals, with one area of the lens for good near vision and one for far vision.
Probably, but there are degrees of far- and near-sightedness. I am nearsighted, and don’t need glasses to read a book. I need a slight prescription for a computer screen at arm’s length, and a little more for distance. I need less adjustment now than years ago, because the trend with age is towards farsightedness, which may cancel some nearsightedness. (In my case, the diopter value has roughly changed from -3 at teen years to -1.5 now.)
When you are young, your eyes can adjust within a wide range. Older, the adjustment range becomes less. So a teenager can get by with a single-vision lens to correct everything, but someone over 60 may need bi- or tri-focals to cover all ranges.
Actually, no. Sarah Palin is middle-aged, so if she is indeed farsighted, unlike younger farsighted people, she can’t use increased focusing power to compensate for her farsightedness.
In other words, middle aged farsighted people (aka hyperopes) lose the ability to see far away as they get older, and they have an even harder time reading up close than plain old presbyopes (aka those with “aging eyes.”) So it’s often a double loss – these are people who have never had to wear glasses before, who find that first their ability to read close up goes, and then their ability to see far away.
Anyone have an idea why I don’t need glasses at all anymore? I’m 57, and I just played a game of basketball yesterday without glasses and didn’t miss a thing (visually speaking)–I saw the other players, and the basket perfectly all game long, and I hardly need my glasses to drive these days, whereas in previous years I couldn’t see road signs clearly nor other cars more than a block away. Now I’m good.
I also don’t need reading glasses anymore–they’re positively annoying, and I take them off whenever I work on a computer. I still lug them around–fifty years of habit die slowly–though it’s often six hours before I miss them. (I guess if I want to drive, I’ll wear them just because my license says I need them, and my vision isn’t perfect, just good enough to drive, so it’s a safety measure, but really I think I’m pretty safe without them behind the wheel.) What’s up with that, and can I count on it to continue? I’ve been like this for a couple of years now.
Not necessarily. I’m farsighted and really only need my glasses for close-up stuff, but a lot of the time these days I still keep wearing them constantly because I just kind of forget that I have them on.
Plus, they give me that irresistible Woody Allen-esque look.
Is there any actual difference between presbyopia and hyperopia?
And is it actually everyone? I thought it was only almost everyone or even just most people.
There is a significant difference between presbyopia and hyperopia.
Hyperopia means, essentially, an eye with a refractive power too weak for its axial length, or the length from front-to-back (cornea to retina.)
Presbyopia means the lens becomes stiffer and less elastic with age, and is therefore unable to change focusing power. We need the greatest focusing power for close-up work; therefore presbyopia doesn’t affect distance vision at all – unless you are the sort of person who uses your lens to compensate for a lack of refractive power in the eye – as many young hyperopes do. So presbyopia has a very unfortunate affect on hyperopes, who now find that, without classes, they can’t see clearly at distance or near. (People with astigmatism of sufficient refractive error suffer the same problem.)
Does it happen to everyone? Yes and no. Everyone loses elasticity of the lens. Some people are not bothered by this to the same extent as others, for a variety of reasons – small pupil size can act as a “pinhole” effect and increase clarity at distance and near, for example, enabling some elderly people to read print (so long as it isn’t too small) without reading glasses.
In pseudotron ruber ruber’s case, a few things might be happening, and it would be impossible to tell without giving him an eye exam. One possibility is that one eye is more myopic (nearsighted) than the other. Sometimes people choose to have that situation created artificially with contact lenses, known as monovision. In that case, he might be using one eye for distance and one for near.
The other possibility is he’s slightly nearsighted in both eyes to begin with – if he can drive without glasses, he probably has vision better than 20/40 (this is true in most, but not all, states.) So maybe he’s slightly myopic, has become accustomed to slight blur in the distance, and uses a combination of slight myopia and the remaining accommodative power of a 57 year old (not much) to be able to see the computer (which generally requires a working distance further away than reading material, and hence less accommodation/refractive power.) If he is, say, a -1.00 myope, and can still accommodate half a diopter with ease, he has an effective +1.50 add for computer use, which is sufficient – but not sufficient to read the smallest print at a closer working distance. Just my guess.
Sorry if any of that is confusing. There’s a reason I had to take coursework in this stuff…
