Glasses or Contacts
February 1, 2004 10:10 AM   Subscribe

Spectacles only? I got a copy of my glasses prescription from my eye doctor, and it says "Spectacles only". I have an existing copy of my contact lens prescription, complete with measurements. If I keep the same numbers but substitute the new sphere measurements, can I order contacts with this prescription?

And on a secondary point, wtf does "spectacles only" mean, anyway? That seems silly.
posted by anildash to Health & Fitness (11 answers total) 1 user marked this as a favorite
No, you can't order contacts with a "spectacles only" prescription. Eye doctors do a contact-lens fitting to give you a contacts-specific prescription, which is good for one year, I think. And then they try to sell you contacts before letting you out of their office, lest you buy from 1-800 Contacts or something.
posted by msacheson at 10:35 AM on February 1, 2004

The prescription you need depends on the distance the lens in from the eye. That's why prescriptions for contacts and glasses are usually different. They might be the same if you have a very weak prescription.
posted by kindall at 10:44 AM on February 1, 2004

Right. Contact fittings are needed because every eye is shaped differently. A direct contact lens needs a different set of numbers because it is directly on the eye, not a couple millimeters away on an indirect surface.
posted by keli at 10:46 AM on February 1, 2004

Anil, wait until you get the one that says, "Coke bottles only."
posted by Mo Nickels at 6:00 PM on February 1, 2004

Contact fittings are needed because every eye is shaped differently.

Not as differently as you'd think, though. Contact lens fit is specified by "base curve," and most lenses are offered in only a couple of base curves. The popular Acuvue 2 only comes in 8.3 and 8.7, for instance. Ciba Focus Night & Day are available in 8.4 and 8.6 base curves.
posted by kindall at 6:36 PM on February 1, 2004

Correct. But both of your eyes may be shaped differently (meaning one may need an 8.4, the other an 8.6), which is what I meant.
posted by keli at 7:04 PM on February 1, 2004

I'd expect that would be rather rare, though.

The last time I got an eye exam, the asinine eye doctor insisted on putting both base curves in and leaving them in while he checked my vision with them. Despite the fact that one was so obviously wrong that tears were streaming out of the eye it was in because the incorrect fit meant that the edges of the lens were constantly scraping against my cornea.

Afterward he started to explain base curves, and I said, "I could have told you what my base curve was, dumbass!"

Won't be going back to him this year.
posted by kindall at 7:57 PM on February 1, 2004

Hmm, I've never had a problem buying contact and/or galsses with one perscription. When I buy contacts I do have to go in for a fotting on top of it though, so maybe that's the difference.
posted by aclevername at 8:38 PM on February 1, 2004

Response by poster: I should clarify, I have the measurements for the contacts, and I know i'm an 8.6 base curve and 14.2 diameter in biomedics 55 lenses, which I want to reorder. The only thing that's changed since the last time I got the lenses is the power of the lens. Am I understanding correctly that even that number is masured differently between glasses and contacts?
posted by anildash at 11:11 PM on February 1, 2004

Best answer: Am I understanding correctly that even that number is masured differently between glasses and contacts?

Can be. I've had prescriptions that were stronger for glasses than contacts, or the other way. Something like half a diopter or a full diopter difference, too, not just piddly differences.

This page
explains some of it. The short answer seems to be that glasses and contacts prescriptions will only be the same if you have a mild prescription and no astigmatism.
posted by ROU_Xenophobe at 11:49 PM on February 1, 2004

Yeah, I have really strong glasses, and even an adjustment to the nosepieces or earpieces (resulting in an ever-so-slight difference in the distance between lenses and eyes) can sometimes give me that "just got new glasses" disorientation for a few hours. The difference between contact/eye distance (zero) and glasses/eye distance is actually pretty huge in comparison.
posted by staggernation at 4:24 PM on February 2, 2004

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