My eyeglasses Rx vs. my contact lens Rx...do they jibe?

January 9, 2017 4:47 PM

Can you determine if my contact lens (bifocal)prescription and my eyeglasses prescription are the "same" ? (links below)

You are not my Doctor.
I am terrible at keeping records (and I will do better in the future).

I started wearing multi-focal contact lenses a couple of years ago and I really love them. In March of 2016 I went to my eye doctor and she gave me two prescriptions, one for eyeglasses and another for the contact lenses. Prior to seeing her I saw a male eye doctor (in the same office with her) and he switched me to the bifocal contact lenses*. I made my last two pair or contacts last a really long time (I'm poor)! I also never got the eyeglasses prescription filled because I do all right with readers from the drugstore (I buy around +2.25 or +2.50).

I placed an order for contacts and I got them today. I put them in and could not read a thing....nothing! It was like having no correction at all. (REALLY too bad because I bought 4 boxes of them and they are expensive). I called the eye doctor's office and they argued with me, telling me that this IS my prior contact lens prescription. (But I know that can't be, because I am able to see and read with the prior contact lenses). *I asked them to check the other doctors prescription and they said they "would have to send for them" (?) Unfortunately I can't find any of my paperwork from my appointment with the other Dr.

I have searched the internet to try to find out how to read eyeglass and contact lens Rx and I am totally confused. The eye doctor's office finally said that I can come in and see someone, but they gave me an appointment three weeks from now! My question to you is...can you read these two prescriptions and can you tell from my eyeglasses prescription what the strength of the bifocal contact lenses "should" be? What I am getting at is that I think Dr. "L" made a mistake and that the bifocal contact lens strength should be 2.25 not 1.25. If anyone here can shed light on these two Rx and whether or not they seem like there is any discrepancy, I would so appreciate it. I'd love to resolve this sooner than 3 weeks from now.

contact lens
eyeglasses

posted by naplesyellow to Health & Fitness (12 answers total)

I'm not your doctor, and I'm not an expert on contacts. I make eyeglasses.

What I'm guessing is that it was either a typo or misreading (incredibly common) or very possibly a mistake based in the fact that your eye doctor is one of those weirdos who write prescriptions in a positive cyl, which is a legitimate method but not the one used by most eye doctors and almost never by labs. It's a certain sort of eye doctor that uses them, and if your two eye doctors are of the two different sorts, it could be that. I don't see any reason for your add power to be 1.25 instead of 2.25.

That's also a weird looking contact prescription, could I possibly see the box? It should be individually labeled. There's no explicit description of the sphere, cylinder or axis and they could also just be pure 1.25 'cheater' contacts which lack your ~+1 sphere power in both eyes.

(Unsolicited, I know, but you have an astigmatism in both eyes, and that has to be made to prescription, readers don't have it. The brain can adjust for a pretty significant range of visual flaws, which is why you do fine without real glasses, but it means that you are constantly straining to correct your axis, which is bad. Real eyeglasses with a cyl and axis will simply feel better, even cheap ones.)
posted by neonrev at 5:17 PM on January 9, 2017 [3 favorites]

You need to contact the doctor's office again and tell them that you need an appointment sooner than 3 weeks. They'll have one, you just have to ask again. And again.
posted by radioamy at 5:17 PM on January 9, 2017 [1 favorite]

The more I think about it, the more I think that those contacts are just spherical 1.25 addition contacts (if that was all I had to go on, that's what I'd make), which is just not at all correct and would, to you, seem as though there is no correction. If the box has a prescription label and it does not have a sph or cyl power then that is what has happened.
posted by neonrev at 5:24 PM on January 9, 2017

On those prescriptions "add" is the progressive addition for reading. The 2.25 number you're seeing is the progressive addition, not the base prescription. The contact lens prescription has an "add" value of "high," which corresponds to the one in your glasses prescription (for those lenses your choice of add power are low and high, not number values).

Your glasses prescription includes astigmatism correction (the cylinder and axis values) while the contact lens prescription doesn't. Because of that the contact lens prescription's spherical correction (labeled "sph") is adjusted to be between the uncorrected "sph" value on the glasses prescription and the astigmatic correction, at a value determined to be appropriate for you by your doctor. IANAD but the two prescriptions look similar enough to me, based on the adjustments that have been made for (1) contacts in general, (2) spherical contacts instead of toric lenses, and (3) the options for progressive addition in those contacts.
posted by fedward at 5:30 PM on January 9, 2017

Response by poster: Here is a photo of the box. I feel very stupid reading the answers so far, because none of what you've said makes any sense to me. I am 66 years old and I think my poor eyesight has to do with the "beginnings" of cataracts. (At least that is what the female Dr said to me once). My vision is quite blurry. The bifocal contacts have been GREAT (the ones I had that ran out). Would the contact lens Rx I got recently be considered a mild correction? My eyesight is so bad I can't read the word "SHAMPOO" on the bottle in the shower! I wish I had kept any of the prior boxes/containers/Rx that would prove conclusively that it was a higher strength than prescribed in March. Thanks again for looking at this for me.
Photo of box
posted by naplesyellow at 6:38 PM on January 9, 2017

Would the contact lens Rx I got recently be considered a mild correction?

Anecdata, I don't wear multifocals (maybe they're different?) and I definitely don't want to derail your thread into a one-upping about vision correction, but I (not a doctor, and not someone with cataracts) would definitely consider your correction to be mild, or at least in the range of normal. My prescription fluctuates a bit, but I wear -6.0 to -7.5 and have since I started wearing contacts as a teenager and personally paying attention to the number; I'm 30 now. My glasses have always been in that range as well. I started wearing glasses pretty much as soon as I started school and teachers noticed I was making mistakes from my desk in the back of the room. I can't imagine having good enough eyesight to be able to get by with the readers from the drugstore!

I don't really do anything without correction, not even shower, much less attempt to read there. I've always lived this way, I find this normal and it's really not a big deal. Lots of people have worse. I have a friend who has correction in the -14 range. He also lives a normal life. You just get up, put on your glasses, and leave them on until you go to bed. Maybe take them off in the shower if you want, but memorize where everything is. I usually wear my contacts. Occasionally I'll nap with my contacts in and it's really weird to be able to see clearly right off the bat when I open my eyes; it feels wrong.

If you've always had pretty normal vision, it may bother you, but I wouldn't worry about your eyes failing or having what seems to you to be especially bad vision from a pure prescription strength perspective. I hope this helps your worries.
posted by spelunkingplato at 8:30 PM on January 9, 2017 [1 favorite]

Also, again, I don't know anything about multifocals, but I do have astigmatism correction and your contact prescription looks strange to me (from a non-multifocal perspective). My contacts prescription is like your glasses prescription, with cylinder and axis specified. The contacts are also "toric," which means they are weighted so that they always stay in one direction on your eye, for astigmatism correction. There's a tiny line on them near the edge; they also cost more. I feel like you would know if your last contacts were toric, they would be labeled as such, and someone at some point would have discussed with you your astigmatism. I used to not have astigmatism correction and then I did, and there was a conversation about how these lenses were different and how to best put them in. It's possible to have mild enough astigmatism to not bother correcting for it (I fluctuate from exam to exam), but I'd think they'd talk to you about the change.
posted by spelunkingplato at 8:43 PM on January 9, 2017

Without knowing what the old prescription was, it's hard to know where things have gone wrong here. That box matches the new prescription you posted. Is that the same brand of contacts you wore before? When you saw the doctor and got that prescription did they put you in a trial pair?

If your prescription changed (either in lens or power) and you kept wearing your old lenses, you're only now having to adapt to the new lenses. That adaptation period is why they give you the trial pair, and I've never had a doctor prescribe new contacts for me without putting me in a trial pair while I'm still in the office. I put the lenses in right then and there, they check the fit and the power, and then I have a followup in a few days to make sure they're still working right for me. It is possible your new lenses are a different brand, or aren't fitting in quite the same way, and so the reading power isn't where it should be.

The next time you can't read something, look up for a few seconds and blink a few times (while still looking up) and then try again. If you can read after that, it's possible the lenses just aren't settling properly into place. They'll be weighted and they're supposed to spin and orient themselves correctly, but they might not be doing that for you. If this is poor fit or a bad prescription it should have been caught when they gave you a trial pair. But I don't get the impression that happened, since you're only now filling a prescription written in March. Your best bet is to follow up with the doctor, and in the meantime see if your +2.25 reading glasses will allow you to read while you've got the contacts in. You may need something like a +3 now without contacts.

As for feeling stupid, there are (up to) three measurements in an eyeglass prescription:

1. The sphere, which is the base correction of the lens (sometimes referred to as the distance vision correction). Yours is +1 or +1.25, depending on which eye. By itself, it's not a particularly high number, but keep reading.
2. The cylinder and axis (which I'm counting as one measurement even though they're two numbers). Picture a contact lens held between your fingers, with no pressure applied. It has a spherical shape. If you squeeze it a bit it will bulge in one direction (front to back) and flatten out in the other (side to side). Your eye is effectively a little like that squeezed contact lens; that's called astigmatism. In your right eye, 0.75 cylinder adds* 75% more correction to your 1.0 sphere, but only along the 10° axis specified. Your left eye has a lower cylinder correction (.25) added to a higher sphere (1.25), along the 170° axis. Imagine holding a donut flat in each hand. If you tilt one hand 10° to the left and one 10° to the right, the edge of the donuts facing you indicate the way your prescription is tilted in each eye. In this crazy example the outer circumference of the donut* is the cylinder correction, and the circle you see after taking a bite is the sphere. But wait, there's more!
3. The addition, which is what makes bifocals bifocals, or progressive lenses progressive. It adds plus (magnifying) power in just the "reading area" of the lens. Your addition is 2.25 (or, in the contacts, "high," which is said to be appropriate for the range +1.75 to +2.50).

For contacts there will be two more numbers for how the lens physically fits your eye, the diameter and base curve. Diameters don't really change within brands, and the base curves only come in one or two choices per brand (the base curve you got is the one the doctor prescribed). Your contact lens prescription does not correct for astigmatism so it omits the cylinder and axis values, but it still has a base power and an addition for reading. The uncorrected astigmatism shouldn't make much of a difference, but it will mean that you'll never see quite as sharply with contacts as you would with glasses.

* Just to make matters especially confusing, opticians and the labs that make lenses have mostly changed the way they write these values. Your doctor is an MD and did it the old school way, with the cylinder power indicated with positive numbers (this is what neonrev was talking about). The new way is to write cylinder power with negative numbers, but that also means the sphere and axis values are different. If you imagine the donut from my analogy, this time instead of holding it flat, hold it up on edge, and then tilt it 80° down in opposite directions so it's in the same final position as the earlier example. Same donut, different way to describe it. There are converters to go from plus to minus, but they don't really matter here since your contact prescription didn't include those values anyway.

** The geometric name for the shape of a donut is a torus. A contact lens that corrects for astigmatism is sometimes known as a toric lens. If your astigmatism is minor enough your doctor may choose not to correct it for you when you wear contacts, since toric lenses can be uncomfortable and may drift out of place. Ask Me How I Know.
posted by fedward at 8:45 PM on January 9, 2017 [1 favorite]

You should absolutely not feel stupid, lenses, especially contact lenses, are a very specialized and complicated area. I know people who've worked in the industry 25 years or more who still get mixed up from time to time, and it's also a very individual sort of science, the muscles and the brain learn a lot over time and can mix stuff up a lot. How can you tell for sure why someone isn't seeing right? Anyone who pretends that there is some certain answer to optical lenses because physics says so is a fool. Brains can make really fucked vision work out, and make corrective vision look horrible. Also the words don't make much sense unless you have to visualize the form of the lens.

It's very difficult to actually compare prescriptions across people. I've known people who seen just fine at a -1.50 cyl that's off 4 degrees and .25 in both, and I've known people who get headaches looking through lenses off by less than a degree. It's incredibly personal, and the brain adjusts to a lot of things. But also, for what it's worth, I'm young and that is a more mild prescription, minus the add (which is due to a loss of muscle control that age just does to most people, mostly) than I have as well.

Cataracts at that age are a real concern. I would consult a doctor about it first, obviously, but it would also be unusual for you to have working contacts and non-working contacts because of it. But I'm not a doctor, I just make lenses.

I've contacted my boss and the lady who does our contact orders, and both are willing to take a look and see what they think tomorrow morning sometime. Three weeks seems ridiculous to me as a wait time, but I don't know where you live. I've stop in if you have time and ask for an appointment in person, there may be people who don't show up, or extra time. If you're having problems and have two eye doctors, I'd want to make sure it isn't some mix-up in person.
posted by neonrev at 8:45 PM on January 9, 2017 [2 favorites]

The new way is to write cylinder power with negative numbers, but that also means the sphere and axis values are different.

I'm basically certain that this is what is going on, as this sort of shit happens all the time. There's a lot of steps between the doctor and the order, and using the old way messes a lot of people up if they aren't paying attention. Happened today, as a matter of fact. The old school way is totally out of line with the way lens blanks are made and the software to make them designed, and the boss says that's pretty common with contacts as well.

And yeah, I think we might be dealing with an issue with the differences between different assumptions of different sorts of eye doctors. Personally, I'm technically an optician despite lacking any formal training, I just passed a test, and this differs state by state. It's hard to figure out why a lens isn't working without both the eye and the lenses present.
posted by neonrev at 9:31 PM on January 9, 2017 [1 favorite]

I don't have an answer to the question you asked (and I've found all of those answers terribly cconfusing, too) but as far as having four boxes of the wrong prescription lenses -- the company you ordered from will likely take them back. At least, it's worth asking.
posted by i_am_a_fiesta at 10:04 PM on January 9, 2017

Got some second opinions today at work, and the consensus seems to be that from the info we have, the two most likely issues are a screw-up somewhere along the prescription chain (which could be anything really), or, as the contact specialist tells me, possibly a change in the manufacturing process of the contacts you have, or a change in the brand of contacts.

From a patient to patient perspective, across a population, the wide range of contact lenses can be hyper specific. In eyeglasses, the distance between the physical eye and the lens is somewhat flexible, there's complicated math about vertex distances I need to learn now. But in contacts, which sit directly on the eye, there is much less margin for error (This, I am told, is why the add power is 1.25 instead of 2.25. The lens is directly on the eye and thus there is no need to increase the power to cross any distance. Neat stuff.) and so small changes can mean much more.

As I'm told, there are a lot of differences in how different contacts are made, thicknesses, material composition and creation, the differences are miniscule and toric lenses (which I think those are) are even more personally specific. Sometimes a small change is made on the production side and suddenly some people can't use that contact lens any more. This is like a constant struggle to keep up on, it sounds.

So, the upshot is that you're gonna need an in person thing to try and fix this. There are a lot of ways this could have gone wrong, and there are no obvious resolutions that don't involve actually looking at your eyes and the contacts. Wish I could help more.
posted by neonrev at 10:17 PM on January 10, 2017