Reminder: Definition of Emmetropia in diopters

Just a friendly reminder…

Once you get to a full correction of -0.50 or less (not normalized, but rather full correction in low-ish light) you’re considered emmetropic by most definitions!

The emmetropic range is most often defined as -0.50 to +0.50 spherical equivalent. Being in that range doesn’t necessarily indicate perfect vision at all distances every moment, but it’s generally accepted as normal vision. At that point, even if you technically still need glasses, there would be very few situations in which you’d need to wear them.

My personal long-term goal is to get into this range eventually, and I’m sure the same is true for many.

Also, it seems like the people with low and medium myopia on here who have been targeting the myopic side of this range for their normalized glasses have had the best progress. Seems like people with higher myopia may be able to be a bit more aggressive.


yaaayy! 0.50 diopters less to worry about!

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A truly emmetropic eye (or a hyperopic one where all of the hyperopia is latent or facultative, not absolute) and fully calibrated visual cortex system can see everything from infinity to a “near point” (based on maximum accommodation ability) with constant acuity, such as 20/8. It would also be free of astigmatism or other aberrations. When I was very young, this was the case, as I could see everything from 3 cm to infinity with approximately 20/8 acuity.

Because of presbyopia, I cannot return to such large range of high-acuity vision, but my personal long-term goal is to get to as close as possible to 0 D. If I get there and still have 8 D of accommodation left, I’d have 20/8 acuity (maybe 20/10 from age-related vision degradations) from 12.5 cm to infinity, which isn’t as good as before but is still quite good.

The visual cortex can compensate for a small amount of (transient?) astigmatism, which might be degrading my best possible spherical acuity from 20/8 to 20/13 or 20/15, so clearing that out at the end might also be required. And if transient astigmatism happens often between spherical reductions, then it means it might be necessary to accept lower acuity on the road to emmetropia.

Most people just consider a range (-0.5 to +0.5 or -0.25 to +0.25) to be practically emmetropic, but then their distance vision might be impaired from 20/8 to 20/15 or 20/20 (myopic side) or might have latent hyperopia reducing their near vision range (hyperopic side).

I somehow get the impression that many people here who get to 20/20 don’t bother to clear the final -0.3 D (or -0.2 D or whatever) of myopia.

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Yes, this range is functionally emmetropic for many…to the point that most eye doctors probably consider the range emmetropic for the population at large. Good enough is good enough for most. :+1: