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Is there the highest corrected myopia level (in diopters) that allows you to drive a car in the US? Implying that you get 90%+ vision acuity with that correction (with glasses/lenses), but more than that you are not allowed even if the correction is perfect - due to exceeding the certain D value of the correction (as I know, in Russia it's -8D, but not sure if this applies to the situation when you drive a personal car).

P.S. I'll clarify: it might be your myopia level per se (if there is a ceiling even if you can get 100% VA using glasses/lenses), or might be the maximum optical power of the lenses in your glasses or of the contact lenses you are allowed to drive in. PSS In Russia this -8D limitation works for truck/public transport driving.

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  • I guess the main problem will be that with very high correction values, the viewing range will be the limiting factor.
    – PMF
    Commented May 6 at 12:59
  • @PMF With contact lenses on there's subjectively no change in FOV.
    – George Glebov
    Commented May 6 at 14:07
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    May well depend on the specific US state. Mine says "standards for vision are 20/40 or better in at least one eye, with or without glasses."
    – Jon Custer
    Commented May 6 at 14:41
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    Going by what it says, if vision can be corrected to at least 20/40 in one eye you can get a license. It says nothing about maximum diopters for uncorrected vision. (20/40 is something like -0.75 diopters).
    – Jon Custer
    Commented May 6 at 14:47
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    @BenHocking I've heard about such limitations in the military as well. One reason (which might or might not have applied in your case) was that the military glasses that one would get when entering service where using the cheapest available glass type, which results in very thick lenses for large corrections. If the glass was getting to thick this was impractical, so one was declared unfit.
    – PMF
    Commented May 6 at 17:12

2 Answers 2

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I've gotten driver's licenses in two states: Ohio and California. Both rely on visual acuity, not your diopters or astigmatism values. Both say 20/40 visual acuity. If you need to wear glasses or contacts, they add a restriction to your license that you're required to wear them.

California lists a number of other issues which could cause problems while driving.

Ohio, beyond the 20/40 acuity, also lists 70 degreees of side vision in each eye.

Both states have forms that a doctor can fill out to help you get or keep a license even with some visual issues.

If I remember correctly, FOV (field of vision) in both states by flashing a light off to the side. It's not a stringent test like identify a sign or anything. It's more of a--do you notice something is there so you can move your eyes or turn your head to identify it.

Personal anecdote: My current prescription is between -9.5 up to -11. I also have an issue that my right eye doesn't move much to the right beyond 'straight ahead' due to a congenital (born with) nerve problem (Duane's syndrome). Neither issue has hindered my being able to get a driver's license. Now that I'm starting to get presbyopia, I have 'distance/driving' glasses and 'computer/near' glasses. Optometrists and ophthmalogists can adjust prescriptions for different ranges if you need them.

I was never able to adjust to bifocals. For me, using bifocals with large computer screens requires tipping my head back which was not comfortable for long.

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  • I'm about a -7 in both eyes and have progressive lenses that don't require much head tilt.
    – Jon Custer
    Commented May 6 at 18:01
  • @JonCuster I suspect that you're using smaller lenses than I am. Mine are about 0.75" from pupil to bottom of lens. (and about 1.25" total top to bottom)
    – mkennedy
    Commented May 11 at 2:57
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It’s not based on diopters

There are a number of factors and they differ between private and commercial licences. The hard and fast limits apply to the granting of an unconditional licence, the authority may grant a conditional licence even if you don’t meet the parameters on the advice of your optometrist or ophthalmologist.

In summary for a private licence you need better than:

  • uncorrected acuity of 6/12 (or 20/40 for those still using imperial measures) in the better eye or both eyes together. A conditional licence will be issued if you can meet this with correction.
  • a horizontal extent of 110 degrees
  • no significant loss within the central 20 degrees
  • additional rules apply if you are monocula or have diplopia.
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  • "uncorrected acuity of 6/12 (or 20/40 for those still using imperial measures)" <-- It never occurred to me until just now that 20/20 refers to imperial measures, though of course it does. While I'm generally pro-metric (even though I live in the US), I don't think I could get used to saying "hindsight is 6/6" instead of "hindsight is 20/20", for example.
    – Ben Hocking
    Commented May 9 at 14:25
  • @BenHocking in Russian everyone uses % when talking about VA, or just straight "one" when 100%. I think 6/12 means 50% VA.
    – George Glebov
    Commented May 9 at 15:09
  • @GeorgeGlebov no it doesn’t, it means that what a person at the lower end of “normal” vision (I.e. standardised Snelen 6/6 or 20/20 vision) can read at 12m (20 feet), a person with 6/20 needs to be at 6m (20 feet). It will not correspond to 50% because they are clearly different methodologies.
    – Dale M ♦
    Commented May 9 at 22:34
  • @DaleM Yeah, 6/30 is not 0.5 it corresponds to 0.3 (30%), 20/20 or 6/6 is 100% (1.0), 20/200 is 0.1 (10%), 6/12 I'm sure corresponds to 0.5 or 50%.
    – George Glebov
    Commented May 10 at 12:35

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