20/20 normalized too low, need 20/15 normalized?

I reduced too quickly over the last 6 years, slowing down my progress by a lot. With no glasses (low myopia), there was lots of unclearable multiple vision but no blur.

In 2015, I was X-1 and X-0.5 by cm measurements, and the optometrist prescription was X-1.25 with -0.25 cyl and X-0.5 with -0.5 cyl. I was using undercorrection with old glasses (pure sph, no cyl, 0.25 D gap between eyes) and then lower equalized glasses, but I now realized that I reduced too quickly.

In 2018, the autorefractor showed I had improved to X spherical equivalent (probably -0.5 cyl and -0.25 cyl, I don’t remember which eye, but the one with -0.5 cyl had lower spherical), and the optometrist prescribed X sph (equal both eyes with no cyl), probably because the cyl didn’t make much difference during subjective refraction. I could barely read 20/20 with X+0.25 but X let me see 20/20 more easily, as well as 20/15.

Weeks ago, I wanted to resume progress, so I sat closer to the computer monitor and went from 0 to X+0.25 sph (one step reduction towards 0) normalized, and I get a transient astigmatism multiple vision effect: if I look at close objects (closer than 1m to 2m for left eye, 2m to 4m for right eye), I’d see the astigmatism as multiple vision temporarily and quickly disappear, and if I look at far objects, the astigmatism effect would show up and quickly disappear. While my parents drive, I can see an astigmatic effect on vehicle headlights temporarily and disappear, and if I look close, I’ll see the temporary astigmatism, and when I look far again, I get the temporary astigmatism yet again. I feel like my visual cortex changes the cylinder compensation for all distances, giving me a headache. I can see 20/20 or 20/15 on a bright Snellen and 20/30 on a dim Snellen with this normalized.

Last week, the autorefractor showed X sph -0.5 cyl left eye (maybe its spherical equivalent changed by -0.25 D) and X sph -0.25 cyl right eye, which seems related to the 2m and 4m boundaries. Because of my headaches, my parents took me to the optometrist for a general eye check, so they did not write a prescription. The first doctor went through the tests and everything seemed normal. The optometrist saw that I could read 20/20 with X+0.25 sph and did a retinoscopy, but I’m not sure what the result of that was, and he recorded X+0.25 as my refraction because I could see 20/20 with it, and referred to an ophthalmologist. I would believe my refraction has not changed much since 2018.

Does this mean I should go up to X sph normalized until the transient astigmatism and multiple vision clears, even though I would see 20/15 on a bright Snellen and 20/20 on a dim Snellen with them and they were the full prescription in 2018? (I think the answer is yes, so I ordered those glasses and will just not look further than 4m as a workaround until they arrive. The multiple vision effect now seems to be becoming slightly less severe over time, and the distance where it happens seems to increase.)

Would I possibly need to step up twice to X-0.25 normalized if still there’s too much multiple vision? (I think it’ll be tolerable at X, so I hope not. My uncorrected vision seems to be trading multiple vision back to blur.)

If they create an acceptable amount of multiple vision challenge, when will I know when it’s safe to reduce to X+0.25? (I think the answer is when the multiple vision clears consistently plus some unknown amount of time. That raises the question of how long “a bit of extra time at the current focal plane after the ghosting is gone” is. (I would guess 1 or 2 weeks.))

Would it make sense to unequalize to X-0.25 left eye and X right eye, since my left eye cm is lower, and that would compensate for the 0.5 cyl reduction (assuming the autorefractor is accurate)? Or would that be bad and require introducing a 0.25 gap to the differentials? (I think the answers are “no, don’t do it, it’s just natural ocular dominance” and “yes, that’d be bad”.)

(This question isn’t asking for diopter-specific advice, but if you read my intro thread, you can find out that X is -1.5, and my differentials are 0 (no glasses), so a 0.25 gap to differentials would introduce -0.25/0 glasses.)

Assuming the autorefractor is correct (my true refraction is X sph with -0.5x180/-0.25x60 of cyl), and my experience shows it’s close, but maybe closer to -0.35/-0.2 cyl) and detected the transient astigmatism correctly, these seem like the only viable options for normalized:

  • X
    • one eye has about -0.5 cyl to overcome, and the other has -0.25 cyl
    • pros: equalized and no/minimal overcorrection
    • cons: both eyes are being reduced unequally
    • interestingly, this is the optometrist’s full prescription from 2018, so maybe the autorefractor detects transient astigmatism while subjective refraction avoids it through visual cortex compensation?
  • X+0.25
    • one eye has about -0.25 sph -0.5 cyl to overcome, and the other has -0.25 sph -0.25 cyl
    • cons: too much challenge; multiple vision is difficult to manage, despite having no blur
  • X-0.25
    • one eye has a cross-cylinder of -0.25/+0.25 cyl, and the other eye is overcorrected with a +0.25 cyl
    • pros: spherical is very close to full correction, so the cyl should be easier to overcome
    • cons: overcorrection
  • X-0.25/X
    • one eye has a cross-cylinder of -0.25/+0.25 cyl, and the other has a -0.25 cyl
    • pros: close to a spherical equivalent, already available as old glasses
    • cons: introduces 0.25 gap
  • X+0.25 with -0.5/-0.25 cyl
    • pros: simple spherical reduction
    • cons: introduces cylinder and sph equivalent gap, possibly cyl overcorrection; cyl from transient astigmatism should generally not be corrected

I will proceed with the first option when my glasses arrive.

I can’t edit the previous post, but another possibility is

  • X/X+0.25
    • one eye has about -0.5 cyl to overcome, and the other has -0.25 sph -0.25 cyl
    • pros: close to 0.25 reduction in spherical equivalent
    • cons: introduces 0.25 gap