Slashdot Mirror
Ask Slashdot: Are Progressive Glasses a Mistake For Computer Users?
An anonymous reader writes I'm a daily, all-day computer user and use two 19-inch monitors for my work. I'm at the age now where I need reading glasses, and my optometrist steered me to progressive lenses. I don't need any correction for distance, only reading. I'm trying very hard to get used to them, but I hate them. The focal point seems to be about 1 inch big, with everything around that blurry. Reading books on my iPad is a struggle; I have to turn my head side to side simply to keep the line of text in focus, and when I do that, the page warps and flow in a dizzying manner. I don't think reading should be like watching a tennis match. And using my two monitors at work? Hopeless and frustrating! Has anybody here who uses either very large or multiple computer monitors figured out how to comfortably use progressive glasses? Or are they simply inappropriate for this kind of use?
dont use it. Now pay my secretary
have you seen my sig? there are many others like it but none that are the same
What did your optometrist say when you asked these questions?
Just as you, on "expert" advice I got some progressives...hate them. The "sweet spot" is just too small.
I now have a pair just for screen work; much, much better.
Thinking of getting laser corrective surgery, then will need a pair just for close reading.
I'm mainly near sighted, but had been using bifocals. That was very annoying when trying to see a monitor while standing higher than the monitor. Had to get new glasses a year ago so I went with progressives. The place I got them said I could return them within one month if I didn't like them. At first they were very annoying, but after a little over a week I got used to them and now they're great. They work fine for me with multiple monitors. But everyone is different and some people never can get used to them.
After about ten years of struggling with this I've settled on two 27" 1920p monitors, using broad but low +1.5 glasses that I can peer over when I glance at anything else in the room. I can actually work with the monitors without the glasses as long as Chrome is set to 125% zoom, but it's slightly more comfortable with the glasses, since I can then use the default fonts for virtually everything.
No. Well...maybe. Actually, yes. It really just depends.
I suspect you have a very high correction. My corrections are +1.50 and +1.75 or thereabouts, and I have had progressive lenses for years. They work fine without the problems you describe. My wife, however, has corrections of around +8.0 in both eyes and could never make a go of progressive lenses for the reasons you state. Eventually, she decided on Lasik surgery, which has unfortunately not really gone well -- we're over six months out from the initial surgery and she still needs glasses. She's one of the 1% or so for whom it does not work on the first try.
Good luck.
Dog is my co-pilot.
I have a pair of bifocals (non-progressive, as I don't wear them often). My opthamologist recommended normal bifocals over progressives as I usually wear contacts (only need glasses for reading). He said that the progressives take quite a while to get used to.
I use a single-prescription pair of reader glasses (-1.5) for computer work -- and they are less than what I use for reading books and newspapers (-2.0) as I usually sit further from the monitor than I hold printed material for reading. My opthamologist recommended the cheap ones from the drug store as opposed to a custom made pair. He said that's what he generally recommends unless someone has a dramatic difference between eyes.
I feel your pain. I wear progressives, and for my first pair, the optimal focal area was ridiculously small just as you describe. A couple of years ago I went to a new optometrist and explained that I wanted glasses that had a more natural feel for close viewing. That 'spot' effect isn't there, and I love them.
I had a similar problem with bifocals. My optometrists and I settled on a pair of glasses for working on my desktop computer which were corrected to three feet, my usual distance from my monitor. I find they are also useful for reading off paper, too.
See your doctor for a single-vision prescription for the distance from which you use your monitor.
I would suggest UVA/UVB filtration as well as polarization
Polarized lenses often don't play well with LCDs.
dont use it. Now pay my secretary
Really. If you only need glasses for reading, then get a $2 pair of reading glasses and only use them when you read.
More generally, if your glasses are not helpful when using a computer, then, while using a computer, TAKE THEM OFF.
I'm not a big fan of progressives either. Got a couple pairs last year, but as I type this I'm wearing my old glasses, I find they're better for computer work.
Never let a lack of data get in the way of a good rant.
AC author should go to his nearest CVS (or rite-aid or whatever) and pick up a cheap pair of reading glasses to try. Hell, you can find some at your local $0.99 store. Test them out for reading.
I opted for a pair of Birth Control Glasses (as my wife calls them). They basically look like 'Santa' or 'Ben Franklin' glasses. Little half-sized rectangular lenses that sit at the tip of my nose most of the time. I just look over them for EVERYTHING except reading. When I sit down to work or read a book I push them back up to the bridge of my nose and read comfortably. They ran me something like $4. For "events", I have a normal looking pair of bi-focal glasses (not progressive). They are just clear glass on top and 1.25 mag on the bottom (those I spent ~$40 -- they are also transition lenses). They look decent for weddings and parties where I wont embarrass my wife (heh).
The reason why *I* opted for this is because I HATE taking glasses on/off all the time. This works for me. You might find that glasses with some type of string or cord that hangs at your neck works for you. Or glasses you hang on your collar when you aren't reading/working works for you. The point is that there are cheap alternatives and it's easy to test.
I've also tried progressives and don't have a problem with them -- you just need to learn to use your neck in place of your eye muscles. Tilt replaces eye focus. I prefer my little glasses right now, but I may move to progressives eventually.
I have the same problem as the OP with age related astigmatism and my optometrist suggested progressive lenses. One thing my optometrist was clear to point out was the limitations of the cheaper progressive lenses, where the area in focus was narrow. More expensive lenses offered a much wider field of view, which is what I purchased, but they weren't cheap at $800. The only downside to the lenses I bought was significant barrel distortion on the extreme edge of the lens.
For general use I love my progressives as I can drive and read with the same pair of glasses. I do keep several pairs of general reading glasses around for reading and computer use.
This site has a great comparison, at least for Nikon lenses:
http://www.nikoneyes.com/produ...
Sorry if that came off a bit harsh, but it should be fairly obvious that multifocal lenses are not suited for viewing objects at a fixed distance. Everyone I know with 'progressive' lenses dislikes them; they find them disorienting and only wear them because they want a single pair for all purposes and hate the look of bifocals.
Your eyes are not something to be trifled with; get a pair of proper conventional lenses that suit the distance you will be working at and save yourself the misery of 90% of your vision being out of focus all the time.
How can I believe you when you tell me what I don't want to hear?
With proper, prescription lenses, the lenses are designed to accommodate your eyes. That means you may have a +0 (non-corrective) and a +0.25 or a +1.75 and +1.25. Interpupiary distance is also important: poorly-centered lenses are the cause of painful headaches. All in all, prescription lenses, even prescription reading glasses, are vastly superior to off-the-shelf bifocals.
I got transition lenses in a single-focus design, and I hate them. They're fantastic, except when they get dirty every 5 minutes, get a burrito shoved into them (they're further from my face than my eyes are), or cause my eyes to water. I plan to have contact lenses fitted; this will be more annoying at first, but will have the incredible advantage of being cleaned every 11 seconds, as well as providing a larger field of view. Silicone soft lenses transmit enough oxygen to safely use them for 30 days straight, rather than removing them at night time; I can elect to remove them at night if desired, but I'll still minimize the risk of complications by providing oxygen permeability similar to not having lenses.
Optometry is hard. Some of us are decisionary maximizers, so it's hard even being the patient!
Support my political activism on Patreon.
I wear progressives as well and they are terrible for computer use. I have to tilt my head way back to focus on that little sliver at the bottom of the lens - and then move my head from side to side across the screen. After about an hour of that I was getting a stiff neck. So now I have two pair. One pair of progressives for everyday use and a second pair that are focused for about arms length that I use for the computer.
It's a bit of a hassle changing them back and forth but it's better than what it was before.
I could not get used to them, so I went back to regular lenses.
It sounds like you may need regular glasses just to wear for close work.
For those of us who are near-sighted, we just need to wear glasses when driving or watching TV, and take them off for close work. I suspect you could do the opposite. If not, maybe you need two sets of glasses, one for close work, and another to see clearly at a distance.
More generally, if your glasses are not helpful when using a computer, then, while using a computer, TAKE THEM OFF.
You said that wrong . It should be:
More generally, if your glasses are not helpful when using a computer, then, while using a computer, . . .
TAKE THEM OFF.
YEEEEAAAAAAAHHH!!!!!
We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
I got progressives 20 years ago and it has taken some learning to get best use. Here are alternatives:
1. Get simple, fixed focus lenses for screen work. This is the absolute best vision quality.
2. The big tip: Forget about stylish narrow lenses. They don't have enough vertical space for progressives to work well.
3. The really big tip: Make sure that your optician doesn't set your normal vision spot too low on the lens. That crams all the progression in the bottom third of the lens. My normally head position is slightly "chin up". I make sure I'm looking at the optician slightly "chin down" has he places the mark on the lens for normal vision.
Presbyopia is hell.
I had progressive trifocals for a while. I kept them for a couple years...you get used to them. But, the last time I got a new prescription, I told my doctor that I didn't really think I needed them. He agreed. I'm back to normal lenses, and saved a bunch of money.
The correct answer is 42.
Like you, I used a pair of progressive glasses and hated them. When it came time to replace them, I got the optometrist to write out three prescriptions:
1. Distance use as in driving or moving about.
2. Medium-distance for computer displays
3. In close for reading and reading only.
Three single-vision glasses have proved far better than those progressive lenses. If money is tight, look into buying them online.
I'm lucky enough to still have great eyesight at age 42 (still use the good old-fashioned 6x13 aka "fixed" font in my xterms on my 108 dpi monitor).
However, my mother got progressives at one point, and wore them for a very short time before replacing them. She plays church organ, and has to be able to see music, keys, stops, and (optionally) the choir director. Different organs have different numbers of keyboards (called manuals), and with more manuals, the music stand just gets farther up and farther away. She has different pairs of glasses for 2, 3, or 4 manual organs. She tried progressives, but they were terribly distracting; she also tried traditional bifocals, but they didn't really work either.
Every time I think about getting Lasik surgery or similar, I think of Bill Gates .... And so far, it hasn't.
Some people are just squeamish about a laser burning away their eyeball tissue. You should not assume Bill made the decision based on logic. Also, some people just aren't candidates for LASIK. I had it done (very satisfied) but my wife was told her lens was too thin for the amount of correction she needed.
Coke-bottes: think lenses generally used by far-sighted people who need glasses to see in focus up close.
Bi-focals: have a half-circle shaped area in the bottom of each lens at a different power (for reading) while the rest of the lens is set for regular viewing
Progressive: has the regular lens gradually change to reading power so you don't have the tell-tale line (and power jump) associated with bi-focals.
I refuse to sign
I had the exact same experience as yours with my first set of bifocals. What solved my issues with it is getting what's called a computer grind on the lens. This type of grind widens the peripheral view while sacrificing a bit for reading paper based documents. Since I don't do anywhere as much book reading as I do computer, this was the perfect tradeoff.
The computer grind in the industry is well understood and not the exact technical term they use, but it helps them understand the type of lens grind your looking for.
Hope this helps a bit...
TAKE
THEM
OFF
Coincidentally, the same eye chart as seen in Naughty Optometrists 4.
systemd is Roko's Basilisk.
Don't use progressives or bi-focals. Do this:
Take a tape measure and measure the exact distance to your monitors when working.
Go to an optometrist and get a written prescription for that exact distance (bring the tape measure with you*) including the "PD", pupillary distance, at that range. Do not buy the glasses from them.
Go to Zenni Optical ...and order some $6.95, single vision prescription glasses from them that fit your PD size.
http://www.zennioptical.com/u6...
Add the standard anti-reflective coating for $4.95
For about $12 you have custom computer glasses.
* Yes, I actually do this. And, yes; I'm a nerd.
I've been using glasses for 40 years now (myopia) and staring at computer screens for 30, and everything went fine.
Three years ago presbyopia arose, and I took a pair of progressive lenses.
Learn to move your head, not your eyes.
Basically, re-train yourself.
Mastering the English language is fucking easy: all you have to do is to put an f* word in every fucking sentence.
Been doing this for 10 + years.
Regular Progressive Lenses have very little width in the mid-vision which is used for computer screen viewing. Wide Corridor Progressive Lenses have a much wider view area in mid-vision.
Talk to your optometrist. Some lens brands to ask about: Definity by Essilor and Unique Digital by Kodak. Also get anti glare coating.
Wide Corridor Progressive Lenses are expensive, but worth it, if you are using computers for a living.
Yeah, but contact lenses won't work for close-up stuff. Contacts are for when your eyes are the wrong shape; the reason older people can't read well is because their intraocular lenses are no longer flexible and they can't focus on close-up things. Contacts won't help with that; if you put contacts in to correct that, you won't be able to see anything farther than arms' reach. And unlike bifocals/progressive-lens glasses, you can't really orient contacts so that a region with different correction is at the bottom.
That sounds like a problem I'll have later, and not the problem I have now.
Support my political activism on Patreon.
And unlike bifocals/progressive-lens glasses, you can't really orient contacts so that a region with different correction is at the bottom.
I don't use them specifically and couldn't tell the OP if they would help their specific situation, but there are bifocal contacts on the market now. I do use toric astigmatism lenses in one eye which are similar, they're designed in a way that causes them to settle into a certain "up" and "down" orientation when installed.
This
Look at what happened here: You needed new glasses, your doctor suggests progressives, which you try and don't like. Then, instead of approaching your doctor about the issue, you post on /. instead. Maybe you're just looking for a second opinion, but it sounds like you're not comfortable talking to your doctor. You should find a doctor that you can bring up these issues with. Also, your doctor should have asked you about what you do all day (reading the iPad, using your computer) and offered you choices based off of your health and habits, not just your health alone. Just my two cents.
I always figured coke-bottle referred to lens thickness.
Pre-PRK, I had horrible near-sightedness (-7.50 or so), and referred to my glasses as "coke bottle" due to the thickness. As in "as thick as if they were cut from a coke bottle".
General Relativity: Space-time tells matter where to go; Matter tells space-time what shape to be.
I started life with coke-bottle glasses, and then got contact lenses right after high school. Now fifty years later, I have just stepped up to implanted lenses. These give me crisp distance vision again, and the Milky Way at night, with no more obscuring glare rays coming out of oncoming headlights. We're a Dark Sky Community, and I can now see M31 naked eye, which I never could reach before.
But implants are fixed focus, so I have to pay close attention to near-diatance correction. I bought Walgreens readers for the computer/reading distance and another pair for the "TV distance" of ten feet or so. This combination gives me a large focus area in both modes at very low cost.
1. driving and long distance, like TV across the room.
2. Near distance, like Computer monitor, stuff on the table I am eating.
3. Reading, 1-2 feet. I use this for reading or working in detailed model assembly.
The long distance makes a big difference when driving at night. Otherwise, change is not required all the time, I can adjust close enough for a bit with any set.
I never could get used to head bob, and pointing my nose at the ceiling to read text on a monitor was crap for dignity.
Try a few options, and look for cheap prescription glasses from China. (You can get 3 pairs vs one at the local Dr's office)
Mclae.
Reading glasses, those off-the-shelf from a rack with a positive prescription, are not for those that need prescription glasses. They are for older individuals who still can focus at distance, but who have lost the muscles and lens plasticity to focus their eyes on closer objects.
The eye becomes able to focus on a smaller range of distances in older age, and for a person with good vision who has not needed prescription glasses, this might mean they can focus from infinity to 100 cm instead of infinity to 10 cm of their youth, making reading a book difficult.
The majority of those needing prescription glasses are myopic, or short-sighted, meaning that they can focus well on close objects, but cannot bring far objects into focus with their eye's lens. They will never be able to see far objects such as the stars clearly without optical correction. Unfortunately, after correcting the vision with prescription glasses, the same problem also occurs in older age, individuals can no longer bring closer objects into focus while wearing prescription glasses.
Simply taking the glasses off allows for seeing close objects again, but is suboptimal. First, the prescription glasses likely also correct for astigmatism, another type of distortion in the eye's lens or shape. Secondly, uncorrected vision in people that are quite myopic, such as myself at over -4, means that I can read a book when held a bit closer than would seem normal, but cannot focus on 2x24" monitors when they are 0.5m away, computer monitors are too far away to see. I would travel the world in a bubble where only things 15" or closer can be seen without glasses.
When the eye's lens becomes less plastic in older age, this may mean that the 0.5m monitor can neither be seen cleary with traditional prescription glasses or without correction. A second pair of glasses could be tuned for things 0.5m-5m away
The problem with bifocals and progressive lenses is that they assume you are looking down to see close objects. For those that do close-up work, from SMD soldering repair to dentistry as well as individuals working in front of monitors, they are not a good solution, as the work is directly in front of the eyes.
One practical solution for computer work is 40" 1080p monitors at a farther distance. This takes research when subsituting a television, because many HDTVs that one might try to use at 1920x1080 do not have clear 1 to 1 pixels as advertised, even with digital input.
They are weighted, so under normal use they properly orient themselves.
Let Microsoft know, whether it wishes us well or ill, that we shall pay any price, bear any burden, meet any hardship
BCGs were popularized by the massive, rugged glasses issued for free in the military, but, by definition, they're any glasses that will ensure that nobody will want to procreate with you. BCGs come in many styles, but they're all incredibly ugly.
Totally agree. I also happen to have been in the OP's position.
I too went down the progressives route when I had began to have more trouble reading. They were great for books where the near focus area was well designed, but for computer use all they do is give a clearer view of the keyboard.
Now I have reading glasses and regular glasses. If I have a long day at the screen, I'll be wearing my reading glasses. I can still use them during breaks as there's not a a great difference in my reading and far-sighted prescription, but the difference for screen work is very noticeable and helpful.
The problem with bifocals and progressive lenses is that they assume you are looking down to see close objects...
I wear progressive lenses and they work very, very well with my laptop + external monitor setup. The key is properly positioning the monitors. Yes, the monitor needs to be lower than you may have positioned it prior to needing reading glasses; but, it's really not a problem to position the laptop and external monitor to accommodate this.
Since you're on /., you probably will care to understand the Minkwitz relationship:
deltaA/deltaX = 2 × deltaM/deltaY
where A is the astigmatism created by the lens, M is the power of the correction provided by the lens, and X and Y are the usual coordinates. Thus progressive lenses always get blurry in direct proportion to the difference between your near and far correction, and in inverse proportion to the vertical distance between the near and far sweet spots.
In practice, some advanced techniques such as grinding both sides of the lens and applying wavefront or raytracing optical simulations can make the problem less noticeable (mainly by moving the worst areas from one spot to another). Some brands of lenses are better than others, and some labs do a better job of making them than others. If you go for progressive ("PAL") lenses, ask to see the "occupational" lenses from several different manufacturers. Learn how to see the "invisible" manufacturing codes printed on your lenses.
My solution at the moment: fixed-distance computer glasses, plus Hoya Summit iQ PAL lenses adjusted to increase the size of the reading zone a bit.
The coke-bottle tickness for glasses can now be much reduced by using high-densidy (and now even ultra-high-density) glass/plastics which have a (much) higher than normal refraction index, The higher refraction index means that you don't need as sharp a curve (and, thus thickness) to achieve the needed focus correction.
A you get older, your ability to change focus for various distances reduces, and so multi-focal lenses start to become valuable. When you first get them, they suck, but as your focus ability declines, they can become more useful. Bifocals (and, similarly progressives) are meant to give you easy access to reading at short (book) distances. Progressive lenses have two advantages over regular bi/tri focals:
The problem with progressive is that (as pointed out), they have a smaller sharp-focus field, at any distance, and they take more getting used to. (once you get used to them, they are, actually, pretty useful for a lot of things)
One problem for computer users is that -- especially for desktop uses, we often are reading at mid distances -- neither far focus nor book distances. This is outside the historical "Best Practice" for the optometric profession. The first time my mom 'surprised' me with progressive lenses, we had a long talk about how my distances were not 'normal'.
What I would suggest doing is talking to your optometrist about the standard distances you encounter at work. (use a tape measure and actually MEASURE the distances), then come up with a bifocal pair for those> distances... having some hard numbers will also make it a bit easier for your optometrist to determine whether multi-focal lenses are even a good idea. This would probably also mean talking to a real optometrist, and not just an optician (essentially just an optical technician).
The probable best result (my guess) would be two pairs of glasses -- one set for work distances, and another set for 'normal' uses. If you go that path, you might want consider avoiding the 'pretty' stuff for the 'work' pair (i.e. don't bother with really high density glass, or anti-reflection coatings) It'll make the second pair that much cheaper.
OS Software is like love: The best way to make it grow is to give it away.
Thanks for the elaboration, so there's basically four different styles of glasses? Is there another 'professional' or 'official' name for normal glasses or they're basically just 'glasses' and we refer to everything else with those names? I expect there's probably a more professional name than 'coke bottle'.
"Coke Bottle" is a pejorative term referring to the lensing effect on the persons eyes in order to correct their vision. The most common reason, historically, for "Coke Bottle" lenses was cataract surgery to remove the lens of the eye, before we had the ability to replace the lens. Mostly they are provided to very small children these days, when cataracts occur earlier, and general replacement of the lens is contraindicated.
The generic professional term for all non-vanity based glasses is "corrective lenses".
There are various lenses for various conditions:
- "myopia" is near-sghtedness
- "presbyopia" is far-sightedness, and if age related, is usually corrected by over the counter "readers" or "reading glasses"
- "macular degeneration" can be age related, or caused by a number of other conditions, such as diabetes, and results in damage from the center of the retina outwards; special glasses can "work around" the problem by focussing all light as a ring around the retina outside the area of damage, and depend on the ability of the brain to reintegrate it into a normal field of view.
- "Keratoconus" is a cone shaped cornea that will prevent a full field of view, since light no longer focusses un the retina; unlike macular degeneration, there is no retina damage, and this is fully correctable with special lenses.
Generally, if you care about thee things, or just find them interesting, you can always stop by a not-very-busy Len Crafters or other similar store, and chat up their optometrist or opthamologist, or just read about them on the net.
I have been near sighted since early grade school, needing pretty strong correction. I have probably used more than 100 prescription glasses over the years, including various bifocals and progressives.
I did okay with my first pair of bifocals, from about age 40 to 45. I was building custom computer systems and repairs, so a mix of close-up bench work and general vision.
Between 45 and 50 I was doing more classroom and group support and the bifocals were not working well for this. I was having to do a lot of middle distance work as well as close up and far distance. The job required standing at the back of the room and scanning client/student computer screens where distances ranged from 4 feet to 30 feet. Shifting focus in those middle distances was very fatiguing, which made me grumpier than my usual lovely self, which did not win awards from the managers. Fatigue from eyestrain can develop without you being aware of it; you might have a kind-of, sort-of headache or you might just get more obnoxious without realizing what's happening.
Progressives worked well for me, after I deliberately set out to learn how to use them. Your neck gets more of a workout, since you need to tilt your head to bring things into focus. It takes a few days of deliberate practice to get the habit. It is not natural for humans, though I'm told that it is common in other species. Horses were mentioned. I never really looked into it. Once I learned how to use them they were a delight: I never before had such good vision at all distances.
I am now retired. I wear contact lenses set for distance vision and carry reading glasses with me. I still have progressives as a backup. The contacts are partly vanity: near-sighted eye glasses make the eyes look a little smaller than is natural, in a sort of reverse-cute ugliness. But mostly the contacts are better for photography and outdoor sports (I can wear proper hazard glasses when bicycling, etc).
TL,DR SUMMARY: Progressive lenses require doing some training to learn to position your head correctly for different distances. They are very much worth the effort if one is constantly having to shift between middle distance viewing as well as far and near. For photography, hiking, bicycling, kayaking, etc the best is contacts set to make one mildly far sighted, and carry reading glasses.
Will
I wish I'd been smart enough to have figured this out during my teenage years. Got glasses at twelve for being barely nearsighted, but kept wearing them when doing up-close tasks like reading and using the computer. I think my eyes got lazy with the correction and I made my vision worse. In the last few years I've started taking them off when indoors when I'm going to work on an arms-length task and I've found that my distance vision seems to also be improving a bit.
In really bright light I can see further without my glasses than in dim light, and I'm starting to wonder if I could pass a driving eye exam without my glasses. Haven't had a whole lot of desire to try, but it would be nice, in case I break or lose my glasses and need to get home without them.
Do not look into laser with remaining eye.
I have one toric lens contact for mild astigmatism. If I'm laying on my side for a while to work on the car or take a nap, my vision will be strange for a minute or so when I straighten up. They might not be the best choice for someone into extreme sports, figure skating with lots of high speed twirling, aerobatic pilots, etc.
Will
I should have said that coke-bottles are the ones that make peoples eyes look big from the other side (ie, make the wearer's eyes look big when you're not the wearer). I should have also included Normal: what we consider normal glasses are those for near-sighted people who need them to see far away. These are thinner than coke-bottles and don't have the bug-eyed affect.
Kinda like Milton's glasses in Office Space...
You're messin' with my Zen Thing, man.....
I've never been nearsighted, but I've now needed reading glasses for a decade due to age. Some astigmatism, plus slightly different magnifications for one eye than the other. What works well for me is to have my optometrist prescribe one set of glasses for computer use (with the focus distance set for computer distance, which is longer than the book-reading distance that standard reading glasses focus on), and a combination of drugstore glasses and older computer glasses scattered around the house and car, and a couple of special pairs (like the reading-lens safety glasses and the extra-strength readers for close work.)
So there are computer glasses at home and work that (almost) never leave their desks, and general-purpose reading glasses elsewhere. Most of them come from Zenni Optical, who make decent glasses really cheap ($10-20 for boring frames, unless you need progressives.) The catch with them is that you do need to know the pupillary distance, which your optometrist won't always write down unless you specifically ask, and that measurement depends on the focus distance (so computer glasses will be different than book-reading glasses or distance glasses.)
I also have a few of those skinny drug-store glasses that come in tubes, so you can leave one in the laptop bag or jacket pocket and it won't get squashed. Not perfect, but good enough for short periods of reading, or for restaurant menus.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
- "presbyopia" is far-sightedness, and if age related, is usually corrected by over the counter "readers" or "reading glasses"
Not exactly. Far-sightedness is hyperopia. Presbyopia refers specifically to the loss of "focal accommodation" with age; if you have otherwise normal vision, this usually manifests itself as loss of the ability to focus on close objects.
I've been strongly myopic from childhood. Now, in my early 50s, presbyopia means that without glasses I can only focus on things about six to ten inches away from my eyes, instead of things from two to ten inches away. With glasses, I can still see normally to infinity, but I need bifocals to cover both far and near ranges -- unless I hold the target up close and peer under my glasses.
If you start out with hyperopia (far-sightedness), and presbyopia sets in, you may not be able to focus at any distance -- your nearest focus distance may be beyond infinity.
Coke bottle glasses...think Bubbles from Trailer Park Boys.
Remember 1/object_distance + 1/image_distance = 1/focal_length ?
If you have your screen at R meters away, add (1/R) to your lens strength in diopters. Diopters are 1.0/focal_length in meters. That will give you the same comfortable image_distance at your eye when looking at your screen.
Suppose you have your monitor 0.5 of a meter away, and you use -5.0 diopter glasses because you are short-sighted. You add (1/0.5) = 2.0 to -5.0 diopters and get -3.0 diopters. The person who had -5.0 diopters and used -3.5 diopter lenses for computing work probably uses a screen 2/3 meters away. If you are short-sighted, the diopter values should get smaller in magnitude; if you are long-sighted, the diopter value will get bigger.
Add 2 diopters if your screen is 50 cm away.
Add 1.5 if your screen is 67 cm away.
Add 1 if your screen is 1m away (a bit far, but maybe you have a big monitor)
Hot damn, that school physics is actually good for something! Too bad they had to black out the lab to show us, and we all fell asleep. Now, all I need is some frictionless pulleys and massless string...