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pinecrest
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Post by pinecrest » Sun Oct 06, 2013 10:02 pm

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livesoft
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Re: Getting prescription of old eyeglasses

Post by livesoft » Sun Oct 06, 2013 10:05 pm

Take the old eyeglasses into your eye doctor the next time you see them and tell them what you told us here. They can just figure out the prescription from the lenses directly.
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JamesSFO
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Re: Getting prescription of old eyeglasses

Post by JamesSFO » Sun Oct 06, 2013 10:05 pm

Most places will just put your glasses on their little measurement unit and tell you what they are.

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Post by pinecrest » Sun Oct 06, 2013 10:14 pm

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Re: Getting prescription of old eyeglasses

Post by livesoft » Sun Oct 06, 2013 10:19 pm

pinecrest wrote:Livesoft, the thing is, I don't need an eye exam and don't want to pay for one. Will a doctor be willing to just take someone off the street and figure out their Rx? I'd be willing to pay for it, but I don't know if they'd consider that a waste of their time.
But you also don't need this information right away either, so just wait until you have an eye exam --- even if it is 10 years from now.
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donall
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Re: Getting prescription of old eyeglasses

Post by donall » Sun Oct 06, 2013 10:52 pm

I would go in for an eye exam and ask to have my prescription on my old glasses determined. Best to have one's eyes checked more often than once every ten years. I think the recommendation is one exam every year or every two years.

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Re: Getting prescription of old eyeglasses

Post by Sheepdog » Sun Oct 06, 2013 11:33 pm

In my state opticians must have your eye care provider written prescriptions, not over one year old, to make new glasses. (That is what my eyeglass provider told me, anyway. I contacted my opthamologist to get a new dated prescription copy when I needed a replacement for a broken lense.) They won't make them without that up-to-date prescription. I have read that in California, it is two years, by state law.

By the way, you should check your eyes every couple of years, not just for the prescription, but to check for glaucoma, cataracts and other eye diseases and abnormalities. Your eyes are precious, aren't they?
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Post by pinecrest » Mon Oct 07, 2013 12:05 am

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Mudpuppy
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Re: Getting prescription of old eyeglasses

Post by Mudpuppy » Mon Oct 07, 2013 12:14 am

Even if I purchase glasses at the eye doctor's office, I always ask for the prescription on paper. This helps with my record keeping, and I keep it in my wallet in case something happens to my glasses while I am traveling and I need a replacement pair. A little late for the OP I suppose, but something to keep in mind for the next eye exam.

And to echo what others say, they can measure the prescription from the lenses, although I have had an eye doctor in the past claim the machine is not as accurate as having a copy of the prescription. I have no clue how accurate this claim was though. If you go to a new eye doctor and don't have your old prescription, they will normally check the lenses for free, just so the doctor can track changes to the prescription.

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Re: Getting prescription of old eyeglasses

Post by supton » Mon Oct 07, 2013 5:16 am

That's funny, I've always been under-prescribed.

It's a bit of an annoyance, really; they ask me to read the lowest line, and I'll stumble over 3 of the 10 characters (or whatever the amount is), miss one or two, because they are fuzzy as all out. Then they'll tell me that I have 20/15 vision and isn't that great? 20/15 my foot, everything's fuzzy at that distance...

I just ordered some glasses from Zenni (Chinese company) and am waiting to see how those turn out.

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Re: Getting prescription of old eyeglasses

Post by nisiprius » Mon Oct 07, 2013 5:30 am

Don't worry about "wasting their time." Or, rather, if you're uncomfortable about that sort of thing AS I AM, "feel the fear and do it anyway."

----☞ Honestly, I think the standard recommendation to have eyes examined every two years is really good advice. I want to avoid medical topics but this is a case where there is an honest-to-gosh condition they can easily and safely detect, that you don't notice yourself until it's too late and your vision is seriously endangered. If you are looking for a benchmark to "see how I am doing vision-wise," what you are saying, really, is you want an exam. Your prescription is only one benchmark. Your ocular pressure is a really important benchmark. So are other things they check. Think about it: the eye is the only part of your body that has a handy little window in it where a doctor can look in and see how your blood vessels are doing.

As others have noted, they can measure a lens on a device called, you'll never believe this, a lensometer. Well, actually I learn from Wikipedia that they just call it a lensmeter these days. That can be, and usually is done by an optician, not an eye doctor. It takes very little time. I mean like a couple of minutes. It wouldn't surprise me if the some places might do it for free as a favor, for example, if your regular doctor is at a big group practice that includes vision services, ask their optical shop. Though I'm sure others will refuse if you're not buying anything.

Second, even if you're not covered by insurance, a refraction costs something like fifty bucks where I live, where costs tend to be high.

As to whether they will "take you off the street and just refract you" I'm not absolutely quite sure. The problem is that if they are not convinced you've had a full exam, they will want to give you a full exam and may be fairly insistent about it. But that's not very expensive either.

I had the opposite problem once. I didn't needed a refraction but I wanted my eyes checked because they felt so dry and itchy, and I was right outside a mall Doc-in-a-Box, and he reluctantly agreed to just do the exam (slit lamp etc.) without the refraction.

Third, even though I'm old and my vision is stable, my prescription has changed enough in ten years that I see much better with my current glasses than my ten-year-old glasses.

Finally, even though I believe myself to be very careful in cleaning my glasses--and opticians have commented on what good shape my old glasses are in--stuff happens; I'm not sure what; even with no visible scratches, new glasses are noticeably clearer than old glasses. Not a huge thing, but noticeable.

I try to remember to ask for my written prescription whenever I get refracted, but often forget.
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frugaltype
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Re: Getting prescription of old eyeglasses

Post by frugaltype » Mon Oct 07, 2013 7:12 am

Where I live, a visit to the ophthalmologist's office for a new prescription only is $30. If you can afford that, you can find out the old and new prescriptions. Years ago I did a what is my old prescription question to a place and they did tell me the measuring thing was not totally accurate. I forget any other details about this.

+1 the recommendations to get regular eye exams if you can afford them. Esp. as one gets older, problems that can cause permanent eye damage can get caught early and fixed or mitigated.

I'm not sure your thought about tracking vision changes is workable. My eyes have changed pro and con as I have aged.

I'm another one where they underprescribe. I can be wildly guessing at fuzzy letters and they count that as reading.

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Re: Getting prescription of old eyeglasses

Post by nordlead » Mon Oct 07, 2013 7:46 am

Find a place with a 30-day guarantee. The place I go to will give you brand new lenses if they don't work for you (even if you just don't like how the frames look). We had a temp optometrist (the normal guy was on vacation) who bumped up the prescription after the exam. We went back, they re-did the test and we got new lenses.

You are in control of the prescription (outside of post adjustments that they shouldn't be making). If a line is blury tell them so, if you think the prescription is too strong, tell them so. Maybe I'm just lucky, but our optometrist is great.

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Re: Getting prescription of old eyeglasses

Post by Epsilon Delta » Mon Oct 07, 2013 2:25 pm

pinecrest wrote: Do smaller eyeglass places just take people in off the street with no history with them?
In my experience yes. In many cities and several countries I've walked into opticians for minor services such as missing screws, nose pieces or bent frames. All of them have been happy to help and most of them do it gratis, in which case I usually slip a few bucks in a charity box on the receptionists desk.

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Re: Getting prescription of old eyeglasses

Post by climber2020 » Mon Oct 07, 2013 2:44 pm

frugaltype wrote:Where I live, a visit to the ophthalmologist's office for a new prescription only is $30.
It brings me great joy when I witness the rare occasion of this word being spelled correctly :D

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Re: Getting prescription of old eyeglasses

Post by Flobes » Mon Oct 07, 2013 2:53 pm

pinecrest wrote: Yup, and I'm looking forward to finding an affordable heath plan under ACA so I can get a full-fledged opthamological exam. (Funny how these plans with high deductables keep people like myself out of ALL doctor's offices! )
My current $5000-deductible individual private insurance includes a free annual complete eye exam including vision, prescription, cataract, glaucoma, retina tears, etc. It's part of the free "wellness" benefits expanded in the last several years, not subject to the deductible, that has brought me into doctors' offices.

I don't yet know whether my new ACA insurance will include vision coverage because I'm still shopping my options. But I'll be checking my eyes regardless; I really want them to be fully functional in my old age.

Also I agree with the other posters based on my experiences: I've had my glasses serviced in many places where I am not a customer, and there's never been a charge. And the only time I had a nonproper prescription, I was retested and the lenses recreated at no charge.

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Re: Getting prescription of old eyeglasses

Post by SPG8 » Mon Oct 07, 2013 3:16 pm

pinecrest wrote:Since I know the title can be a bit controversial, let me say ahead of time that my reason for wanting to know an old prescription is NOT to use it for new frames. In my case, it's strictly for informational purposes. I'd like to use it as a benchmark to see how I am doing vision-wise
Tolerance is typically about an 1/8th, which can easily turn into a 1/4 by the time you walk out of the store. So if you're off in opposing directions on two pairs, could be up to a half.

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Re: Getting prescription of old eyeglasses

Post by gerrym51 » Mon Oct 07, 2013 3:51 pm

:mrgreen:
climber2020 wrote:
frugaltype wrote:Where I live, a visit to the ophthalmologist's office for a new prescription only is $30.
It brings me great joy when I witness the rare occasion of this word being spelled correctly :D

sort of like pseudoephedrine :mrgreen:

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Post by pinecrest » Mon Oct 07, 2013 4:22 pm

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Re: Getting prescription of old eyeglasses

Post by bertilak » Mon Oct 07, 2013 4:25 pm

re lensometer (I like that much better than lensmeter!):

I believe lenses have a nearly microscopic prescription laser-etched into them somewhere near the edge. If memory serves, That is how my eye doctor (low risk spelling!) determined the prescription of an old pair.
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ScarletIris
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Re: Getting prescription of old eyeglasses

Post by ScarletIris » Mon Oct 07, 2013 7:31 pm

Optometrist here. I want to comment on a few points. Hopefully I can stay out of anything that will get my comment or this thread locked.

One tip for getting a good prescription is to have them compare your old and new Rx using a trial frame. I always ask how a person liked their old glasses and read the old prescription using a lensometer. If they had a favorite old pair and brought them along, I read them too. At the end of the exam, I first show them the difference in prescription using the phoropter, then I use a trial frame to simulate the new prescription. Often I have them put on the trial frame, look at the chart and around the room, then switch to compare with their favorite old Rx. I want to equal or improve upon the old Rx. The trial frame is key because you are essentially comparing apples to apples in a natural state instead of one where your peripheral vision is blocked, you are in a state of semi-darkness, etc. I would estimate 98% of eye doctors have a trial frame and most would probably do this extra step for you if asked, though some don't do it routinely like I do.

As to "undercorrecting" the trial frame can help as well; I can hold extra lenses in front of it to show one step stronger or weaker. Sometimes I have to say "this is as good as it is going to get", because an increase or decrease in prescription does not improve the vision any further. A pretty big misconception I hear all the time is "just make it stronger" - too strong is blurry, just like not strong enough is blurry.

Only one component of the prescription is laser etched on the lenses - the strength of a "no-line" progressive bifocal, if applicable. Most places will read the full prescription for you at no charge, though some may be wary due to the encroachment of online glasses sellers. Eye doctors, mainly optometrists, have, as a business model, charged very little for the exam, and made up for it due to mark ups on glasses. The online selling of glasses (with no verification or dispensing requirements) is threatening, but has not gained enough market share to make much impact on the business model yet.

I want to chime in to agree with PP that stress that an eye exam is more than just a refraction. You are doing yourself a potential disservice to not have your eye health thoroughly checked.

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Post by pinecrest » Mon Oct 07, 2013 8:50 pm

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frugaltype
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Re: Getting prescription of old eyeglasses

Post by frugaltype » Tue Oct 08, 2013 7:26 am

climber2020 wrote:
frugaltype wrote:Where I live, a visit to the ophthalmologist's office for a new prescription only is $30.
It brings me great joy when I witness the rare occasion of this word being spelled correctly :D
Firefox's Check my spelling knows all.

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Re: Getting prescription of old eyeglasses

Post by Browser » Tue Oct 08, 2013 11:16 am

Perhaps someone can clarify. I always thought that they read a lens prescription from some sort of optical device ("lensmeter"). But then I observed that there are nearly invisible numbers imprinted in my plastic eyeglass lenses. I seem to recall (but it's a fuzzy recollection) that somebody in an optician's office told me that's what they look at to determine the prescription -- the "optical device" is a magnifier that lets them read the imprinted numbers. Is that right, or am I recalling a weird dream I had once? If that's all there is to it, then seems to me it's no big deal to walk into an optical shop and ask them to do it. I dunno, maybe you can do it yourself.
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Re: Getting prescription of old eyeglasses

Post by climber2020 » Tue Oct 08, 2013 11:23 am

Browser wrote:Perhaps someone can clarify. I always thought that they read a lens prescription from some sort of optical device ("lensmeter"). But then I observed that there are nearly invisible numbers imprinted in my plastic eyeglass lenses. I seem to recall (but it's a fuzzy recollection) that somebody in an optician's office told me that's what they look at to determine the prescription -- the "optical device" is a magnifier that lets them read the imprinted numbers. Is that right, or am I recalling a weird dream I had once? If that's all there is to it, then seems to me it's no big deal to walk into an optical shop and ask them to do it. I dunno, maybe you can do it yourself.
That's for over the counter reading glasses. If you hold them up to a light source at a certain angle, you can see the glass power etching.

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Re: Getting prescription of old eyeglasses

Post by Browser » Tue Oct 08, 2013 11:45 am

Don't mean to hijack the thread, but since there is at least one optimist (er, optometrist) on the thread I'm dying to know why different optometrists come up with entirely different results with eyechecks. I just had two different readings. For my left eye OD #1 came up with a result of -2.75 sphere, -2.75 cylinder, 85 axis. OD #2 came up with -2.00 sphere, -4.00 cylinder, 75 axis.

In my previous exam about 4 years ago, for my right eye OD #1 came up with -4.00 sphere, -2.25 cylinder, 95 axis. OD #2 had -3.25 sphere, -3.00 cylinder, 93 axis.

I'm thinking that if most people had their eyes checked by at least two different specialists they'd observe the same variability that I have in the results. Most people don't do that, and since the brain seems to be so good at adapting vision to whatever we're looking through they never notice.
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Re: Getting prescription of old eyeglasses

Post by frugaltype » Tue Oct 08, 2013 12:16 pm

Browser wrote:Don't mean to hijack the thread, but since there is at least one optimist (er, optometrist) on the thread I'm dying to know why different optometrists come up with entirely different results with eyechecks. I just had two different readings. For my left eye OD #1 came up with a result of -2.75 sphere, -2.75 cylinder, 85 axis. OD #2 came up with -2.00 sphere, -4.00 cylinder, 75 axis.

In my previous exam about 4 years ago, for my right eye OD #1 came up with -4.00 sphere, -2.25 cylinder, 95 axis. OD #2 had -3.25 sphere, -3.00 cylinder, 93 axis.

I'm thinking that if most people had their eyes checked by at least two different specialists they'd observe the same variability that I have in the results. Most people don't do that, and since the brain seems to be so good at adapting vision to whatever we're looking through they never notice.
Every time except once when I've gotten an eyeglasses prescription, it's involved the switching lenses "Which one is better" scenario. The one exception (unless I imagined this), they just did something to measure my eyes and announced that they knew the prescription. Is there such a device?

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Re: Getting prescription of old eyeglasses

Post by bertilak » Tue Oct 08, 2013 12:19 pm

frugaltype wrote:
Browser wrote:Don't mean to hijack the thread, but since there is at least one optimist (er, optometrist) on the thread I'm dying to know why different optometrists come up with entirely different results with eyechecks. I just had two different readings. For my left eye OD #1 came up with a result of -2.75 sphere, -2.75 cylinder, 85 axis. OD #2 came up with -2.00 sphere, -4.00 cylinder, 75 axis.

In my previous exam about 4 years ago, for my right eye OD #1 came up with -4.00 sphere, -2.25 cylinder, 95 axis. OD #2 had -3.25 sphere, -3.00 cylinder, 93 axis.

I'm thinking that if most people had their eyes checked by at least two different specialists they'd observe the same variability that I have in the results. Most people don't do that, and since the brain seems to be so good at adapting vision to whatever we're looking through they never notice.
Every time except once when I've gotten an eyeglasses prescription, it's involved the switching lenses "Which one is better" scenario. The one exception (unless I imagined this), they just did something to measure my eyes and announced that they knew the prescription. Is there such a device?
My eye doctor uses that as a starting point to the typical "which is better" game.
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Re: Getting prescription of old eyeglasses

Post by nisiprius » Tue Oct 08, 2013 12:25 pm

frugaltype wrote:Every time except once when I've gotten an eyeglasses prescription, it's involved the switching lenses "Which one is better" scenario. The one exception (unless I imagined this), they just did something to measure my eyes and announced that they knew the prescription. Is there such a device?
Yes. One of my eye doctors has a little gadget like a stereoscope, you look into it and you see a sort of sunburst image like an old TV test pattern, it looks a little blurry, you hear little gzickety-zicks like R2D2 or a camera autofocusing and it... uh... autofocuses it. What is it called? Google, click, click, wow, you'll never believe THIS one, it's called an autorefractor. They don't use it for the final prescription, though, they use it for a start and then go through the traditional procedure.
Browser wrote:Don't mean to hijack the thread, but since there is at least one optimist (er, optometrist) on the thread I'm dying to know why different optometrists come up with entirely different results with eyechecks.... I'm thinking that if most people had their eyes checked by at least two different specialists they'd observe the same variability that I have in the results. Most people don't do that, and since the brain seems to be so good at adapting vision to whatever we're looking through they never notice.
I'm no eye doctor, but: were your eyes dilated? They called it "dilating" because it enlarges the pupil but it also relaxes the focusing muscles and makes it impossible for you to adjust the focus voluntarily. In some states, I believe, only ophthalmologists are licensed to do this, but in others optometrists can do it, too.

If an eye doctor refracts you without dilating your eyes, there are all sorts of possibilities for you to be unconsciously changing your accommodation and affecting the results. Their exam procedure and the sequence in which they do things is supposed to minimize this. But I think they get more consistent results if they dilate first.
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Re: Getting prescription of old eyeglasses

Post by Browser » Tue Oct 08, 2013 1:03 pm

Eyes were not dilated for either exam. I've had many exams over the years and never had the eye exam after my eyes were dilated -- does anybody do this? The dilation was always done after the vision exam so that the retina can be examined by the ophthalmologist. Both exams were of the "which is better, A or B?" variety; however, OD#2 did use the autorefractor for the initial reading. Both were reputable clinics: first one was a University hospital eye clinic with a top reputation. Second was at the office of an OD, not done by an assistant. I've noticed that the A vs. B procedure leaves something to be desired, since blinking or shifting your eyes somewhat often makes a difference in how clear the letters appear. One factor that might be relevant is that OD #2 said my pupils were unusually small; however, he also said that this often improves distance vision, sort of the same effect you get looking through a pinhole.
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Re: Getting prescription of old eyeglasses

Post by frugaltype » Tue Oct 08, 2013 3:21 pm

Browser wrote:Eyes were not dilated for either exam. I've had many exams over the years and never had the eye exam after my eyes were dilated -- does anybody do this? ... I've noticed that the A vs. B procedure leaves something to be desired, since blinking or shifting your eyes somewhat often makes a difference in how clear the letters appear.
Not mine - dilation has always been after. With the either or thing, I ask them to wait until my eyes adjust to the new "picture."

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Post by pinecrest » Tue Oct 08, 2013 4:57 pm

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Re: Getting prescription of old eyeglasses

Post by Browser » Tue Oct 08, 2013 6:42 pm

pinecrest wrote:
Browser wrote:I just had two different readings. For my left eye OD #1 came up with a result of -2.75 sphere, -2.75 cylinder, 85 axis. OD #2 came up with -2.00 sphere, -4.00 cylinder, 75 axis.

In my previous exam about 4 years ago, for my right eye OD #1 came up with -4.00 sphere, -2.25 cylinder, 95 axis. OD #2 had -3.25 sphere, -3.00 cylinder, 93 axis.
Wow. I'm no eye doctor (obviously), but I'd think a -4.00 cylinder was extremely high for a -2.00 sphere. That sounds like a mistake.
That concerns me. I'd like to hear from someone who is an optometrist about that.
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Re: Getting prescription of old eyeglasses

Post by ScarletIris » Tue Oct 08, 2013 8:16 pm

Resident optometrist here, back from a long day of saying "which is better -one or two?".

In school we actually had a spelling test to ensure we knew how to spell ophthalmologist correctly.

We use a lensometer (either manual or automatic) to determine the prescription from the glasses. I usually do this manually by determining the strength of best focus in the machine and those numbers translate to the prescription. The sphere, cylinder, and axis of the glasses is not etched into the lens but if you have a progressive, "no line" bifocal that number is laser etched into the lens. Normally it is etched in the lower temporal quadrant of the lens and can best be seen using a reflection on the surface of the lens. Some place may have a progressive reader machine (not sure the official name, we don't have one) that is a combination magnifier and backlight to more easily see the etching.

The first step is the "autorefractor", the machine gives us an estimation of your prescription. Some people do end up with exactly what the machine said, but normally I can tweak it a bit better than what the autorefractor suggests, and in some cases (highly nearsighted people and farsighted kids), it tends to underestimate the prescription quite a bit. In the "olden days" before autorefractors, you could do the same thing manually using a slit of light and loose lenses - retinoscopy. While we still learn it in school and are tested on it on boards, I don't use it clinically very often, but it can be helpful for patients unable to position into an autorefractor and/or non-verbal patients.

I recommend getting the eyes refracted before the dilation is done. The only time I dilate before the refraction is when I have a young child that I suspect to be moderate to highly farsighted, because they have incredible compensating/accommodating power due to a very flexible lens. For adults, our accommodative power is much reduced, though not noticeably until 40's and presbyopia hits. There are three components that give an eyeball a certain prescription: the length of the eyeball (within your head), the lens inside the eyeball, and the front curve of the eyeball. Yes, the lens inside the eyeball is controlled by muscles, but if I come up with a much stronger prescription that is perfect when your eyes are 100% medically relaxed, it is going to be too strong for your daily use.

Cyl and Sphere power are unrelated. A patient may have zero sphere power and -5.00 cyl or may have -5.00 sph and zero cyl. But those prescriptions are definitely not interchangeable!

I agree that your Rx seems quite a bit different each time. Some eye doctors will decrease the cyl a bit and increase the sphere in order to make a prescription easier to get used to; the formula is normally decrease the cyl by -0.50 and increase the sphere by -0.25. High cylinder power/astigmatism if done incorrectly can cause feelings of dizziness, wooziness, weirdly 3-Dness, floor coming up at an angle, things being tilted, feeling of being on a ship. I would say high cyl (above -3.00) can be one of the more difficult things to get right, the higher the cyl the more precise the prescription has to be.

-2.75 sphere, -2.75 cylinder, 85 axis. Could have some wooziness due to cyl change with the amount of cyl you have; these first two Rxes are similar other than the axis.
-2.00 sphere, -4.00 cylinder, 75 axis.= Approximately -2.50 -3.00x075 - I would think you would have definite wooziness with a cyl change of 20 degrees
-4.00 sphere, -2.25 cylinder, 95 axis. = Approximately -3.75-2.75x095 This is the one that stands out to me as overall strongest by quite a bit.
-3.25 sphere, -3.00 cylinder, 93 axis.

From this, it seems OD#1 tends to err stronger than OD#2, and that your Rx is getting "better"/less nearsighted since your visit 4 years ago.

Hope I have shed some light while not providing medical advice outside of the scope of this forum. If anyone else has any "ask the optometrist" questions, I would be happy to answer. I'm thankful to share knowledge as I've been soaking up a lot from others here!

pinecrest
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Post by pinecrest » Tue Oct 08, 2013 10:25 pm

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Last edited by pinecrest on Mon Feb 24, 2014 4:37 pm, edited 2 times in total.

Browser
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Re: Getting prescription of old eyeglasses

Post by Browser » Tue Oct 08, 2013 10:45 pm

pinecrest wrote:Thanks ScarletIris. A lot of good information there.

I'm still trying to wrap my head around the fact of a -4.00 cylinder with a -2.00 sphere. I was under the impression that unless one had some sort of "structual" astigmatism problem, that the astigmatism increases as the myopia does. And the progression is like maybe -.25 at a time. Judging by your "A patient may have zero sphere power and -5.00 cyl" comment, I guess that's not true! How would somebody get such a disproportionate increase in astigmatism relative to the myopia? And is there a way to prevent the asigmatism from happening? I assume the old advice about not tilting your head is an "old chestnut", but who knows.
I remain concerned about it also. I have all prescriptions from previous years but am not at home base and don't have access to them. However, I'm pretty sure that this eye (the left) has had a fairly consistent reading of about -3.50 sphere and -3.00 cylinder for some time. Since 3 years ago my vision seems to have significantly changed in both eyes, as Scarletiris points out, with general nearsightedness decreasing for some reason. On 9/13 OD#1 had -2.75 x -2.75 and on 10/13 OD#2 had -2.00 x -4.00. The sphere has decreased in both exams, but #2 seems to have favored a lower sphere with a higher cylinder than #1. The spherical equivalent refraction (Sphere + 0.5xCylinder) seems to be about the same for both, (4.125 vs. 4.00) which I understand is sorta the overall power correction. But I wonder about emphasizing the cylinder so much by #2 in light of Scarletiris' remarks that this degree of cylinder correction might have some weird effects unless it is spot on. Combine this with progressive lenses and it sounds touchy.
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frugaltype
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Re: Getting prescription of old eyeglasses

Post by frugaltype » Wed Oct 09, 2013 6:32 am

ScarletIris wrote: High cylinder power/astigmatism if done incorrectly can cause feelings of dizziness, wooziness, weirdly 3-Dness, floor coming up at an angle, things being tilted, feeling of being on a ship.
Ah, that's why when I got new glasses every year it would take me a couple of weeks to get used to table tops looking tilted, then they would revert to looking normal. And why I started clinging to old prescriptions :-) I thought it was a normal adjustment process. I do go to a different eye doc now, since I moved, and do not have that effect with a new prescription.

pinecrest's later remark about head tilting caused me to look that up, since I had never heard anything about that. Sites that talk about that also talk about reading adversely affecting eyesight. I always thought the latter was on old person's tale? Is it true?

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Re: Getting prescription of old eyeglasses

Post by ScarletIris » Wed Oct 09, 2013 9:45 am

I would say that astigmatism and nearsightedness do progress slowly like -0.25 per year, but not in lockstep. Usually the nearsightedness increases as the axial length of the eye increases as a child grows, adults have more minor adjustments to the power. For a child an increase in nearsightedness of -1.00 to even -2.00 per year is not surprising; with adults, it would be large change warranting investigation. With many adults the eyes shift more farsighted/less nearsighted when you turn mid 40's. The astigmatism changes much less, usually minimally. If someone had an astigmatism change of -2.00 in a year I would be making a note to watch for keratoconus, a degenerative condition where the cornea warps.
pinecrest wrote: How would somebody get such a disproportionate increase in astigmatism relative to the myopia? And is there a way to prevent the asigmatism from happening? I assume the old advice about not tilting your head is an "old chestnut", but who knows.
If you think of astigmatism as in the corneal shape and myopia mainly in the axial length of the eye you see that they are not tied. I would be surprised to see someone go from -1.00-1.00 to -1.25-1.25 to 1.50-1.50, etc. Tilting your head has no effect. The muscles in your eyes actually make your eyes also roll so your eyes are always in same position relative to the floor with any tilt. Actually, other than staring at the sun, which can blind you, there is little you can do to strengthen or weaken your eyes - wearing the correct, wrong, or no glasses will make your eyes feel strained and get headaches, but not change your prescription to need stronger or weaker glasses.

Different doctors have different confidences; some doctors will find the perfect strength, and if the astigmatism seems high, shave it down a little in the final Rx to make it easier to adjust to and so that they have fewer remakes, while other doctors will give the full strength of astigmatism hoping to give you the most perfect vision. OD#1 probably is more cautious, while OD#2 is trying to get the most perfect vision hoping you can adjust to the full cyl.

So astigmatism is where your eye is not perfectly round so your vision is not perfectly round. It's like a carnival mirror where people look stretched. Your eye actually has two different prescriptions and the greater the difference between the two the greater the amount of astigmatism the greater the "stretch" is in your vision. When you have an astigmatism lens it "unstretches" your vision. Think of an O far away, the greater it is stretched (the direction of the stretch is the axis) the more difficult it is to make out. With lenses however there is also a magnification or minification effect as well. Think how a person's eyes will look proportionately larger or smaller behind their glasses than in real life. If you have astigmatism, part of the glasses magnify more than the other part (the more astigmatism, the more this difference in magnification) and that difference in magnification creates a slant if not lined up correctly with the eye.
frugaltype wrote:Sites that talk about that also talk about reading adversely affecting eyesight. I always thought the latter was on old person's tale? Is it true?
Jury is kind of out on that one. Yes, studies hypothesize that reading and extensive near work increases myopia in a population in general, but per person, I would not say people who love reading always have large Rxes while people who hate reading don't need glasses or vise versa. There is a lot of studies being done on the causes and treatments of myopia but there is not a clear answer at this time. Genetics has also been said to be a cause as it can run in families. However, I have seen several sets of identical twins and they have never matched prescriptions.

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