# Buying eyeglasses without an exam

**URL:** <https://boards.straightdope.com/t/buying-eyeglasses-without-an-exam/449287>\
**Category:** Factual Questions\
**Created:** [May 14, 2008, 3:16pm UTC](https://boards.straightdope.com/t/buying-eyeglasses-without-an-exam/449287 "2008-05-14T15:16:37Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Hampshire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hampshire/32/4887_2.png) [@Hampshire](https://boards.straightdope.com/u/Hampshire)\
**Post date:** [May 14, 2008, 3:16pm UTC](https://boards.straightdope.com/t/buying-eyeglasses-without-an-exam/449287/1 "2008-05-14T15:16:37Z")

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Is there anywhere that will make me a pair of glasses using my contact lens prescription that I just know off-hand (no physical prescription).  
My prescription is a -5.5 for both left and right eyes and I’ve been wearing that and reordering contacts with that for the past 8 years.  
Now I just want a spare pair of glasses to wear for a few hours at night maybe once a month to give my eyes a rest and do it as cheaply as possible.  
Anywhere that will do this for me?

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**Author:** ![Scumpup](https://avatars.discourse-cdn.com/v4/letter/s/ce73a5/32.png) [@Scumpup](https://boards.straightdope.com/u/Scumpup)\
**Post date:** [May 14, 2008, 3:17pm UTC](https://boards.straightdope.com/t/buying-eyeglasses-without-an-exam/449287/2 "2008-05-14T15:17:21Z")

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Zenni Optical. They’re online.

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**Author:** ![MarcusF](https://avatars.discourse-cdn.com/v4/letter/m/67e7ee/32.png) [@MarcusF](https://boards.straightdope.com/u/MarcusF)\
**Post date:** [May 14, 2008, 3:25pm UTC](https://boards.straightdope.com/t/buying-eyeglasses-without-an-exam/449287/3 "2008-05-14T15:25:34Z")

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Don’t do it! My contact lens prescription is nothing like my glasses prescription. If I had glasses made to the same prescription as my contacts I would have lousy vision and headaches.

ps I you haven’t had your eyes checked for eight years, I would have thought you are really risking your sight.

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**Author:** ![Solfy](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@Solfy](https://boards.straightdope.com/u/Solfy)\
**Post date:** [May 14, 2008, 3:57pm UTC](https://boards.straightdope.com/t/buying-eyeglasses-without-an-exam/449287/4 "2008-05-14T15:57:13Z")

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I am not an optometrist, but I recall that my glasses strenth in diopters (the -5.5 number you mentioned) is different from my contacts. When I asked my eye care professional why, he explained that it was due to the difference in focal length - a lens sitting on your cornea needs to be a different strength than a lens sitting a few cm past your eyes.

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**Author:** ![Hampshire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hampshire/32/4887_2.png) [@Hampshire](https://boards.straightdope.com/u/Hampshire)\
**Post date:** [May 14, 2008, 4:02pm UTC](https://boards.straightdope.com/t/buying-eyeglasses-without-an-exam/449287/5 "2008-05-14T16:02:53Z")

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Hmmm… yeah it looks like even from the ZenniOptical sight that they need a few more numbers than the basic ones a contact prescription has (SPH,CYL,AXIS).  
Looks like I’ll be springing for an eye exam.

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**Author:** ![Cardinal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cardinal/32/4000_2.png) [@Cardinal](https://boards.straightdope.com/u/Cardinal)\
**Post date:** [May 14, 2008, 5:07pm UTC](https://boards.straightdope.com/t/buying-eyeglasses-without-an-exam/449287/6 "2008-05-14T17:07:55Z")

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They also need to know the distance between your pupils. Walmart measured that for free, for me.