Follow acuity or diopter ratio?

Hey folks. I have a non-diopter-specific reduction/differentials question.

So, I just got my trial lens set and based on what gives me the best differential acuity with the test lenses, my diopter gap is like 0.5D different (less) than what my visual cortex is used to based on the glasses I’ve been wearing for the last few years.

I know that it is not recommended that we mess with diopter gap until we’re focused on equalizing (which shouldn’t happen until we’ve successfully dropped several times) but I wanted to know if we should follow what our acuity shows or if we should always keep to the diopter ratio when making adjustments until we’re specifically working on equalizing?

In other words, when getting new differentials, should I aim to hit 20/30 in both eyes (even if that means changing the diopter ratio) or just do a binocular drop from my current glasses to keep my visual cortex from having to adapt?

It feels like I should follow what my eyes want but don’t want to push the envelope too quickly since my visual cortex may not be ready for it.

p.s., I also asked this on discord but figured I should repost here for anyone else who may have a similar question in the future.

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(i said it’s personal preference and up to your own goals. also that the holy guru blessed keeper of the eight keys says that a 0.50 difference isn’t necessarily worth equalising at all over, because it’s close enough to normal ocular dominance. in the discord server, plug: https://discord.gg/23V99T9)

To be clear, my intention isn’t to equalize. I’m just looking at what my test lens kit says gives me the best acuity in each eye monocularly. The result is that one eye would drop by 0.50 relative to what my prescription shows. That wouldn’t reduce my diopter gap to 0 though, since I’m starting with a 1.50 (or 1.68 if we look at spherical equivalent due to astigmatism) and dropping to a 1.0 diopter gap. This also matches with my cm measurements which give me a 1 or 1.25 diopter gap depending on the day.

My goal is to bring in my depth of field (blur horizon) so that I get equal acuity in each eye at computer distance. Both for reduction of hyperopic defocus and to give me some blur for AF. So this seems like I need to base on acuity rather than prescription.

For years I have been pushing my glasses to the tip of my nose for computer use since my eyes don’t like the overcorrection. That drops my Rx by 1.25 D in one eye and 0.75 D in the other eye (according to vertex distance formula). So this may be part of why my eyes are not following the diopter gap in my prescription.

So based on my gut feeling and what folks are saying on discord, it sounds like I should follow acuity over the diopter gap, particularly in differentials.

So, what can I expect to happen when the full/normalized diopter gap is different than the differentials diopter gap? Is that going to make my visual cortex freak out because it’s constantly having to switch back and forth? Or do I need to plan to order new normalized or full Rx lenses at the same time as a change in diopter ratio?

In my book, what the eyes want and feel most comfortable with always trumps the orthodoxy. What works for most people does not work for all. But this is the opinion of a black swan. :wink:

You may find that when you come to measuring for norms you will want to reduce the diopter gap as well - or not. The visual system can quickly adapt to a larger diopter gap than required, enforced on it by over-correction of one eye. Here again, actual acuity as measured for each eye should be the best guide.

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So after this discussion and several more experimental frame combinations using my trial lens kit to confirm my measurements, I bit the bullet and ordered replacement differentials that take into account the 0.50 diopter difference in my correction for near vision. Using the test lens set, the new configuration will get me at just under 67cm to blur in both eyes, where my current configuration gives me different distances in each eye (one at 73mm and the other at 53mm).

The ones I’d ordered from Zenni haven’t even shipped yet, but apparently it is too late to cancel or change. I ordered these from Goggles4U since they had a 65% off Christmas sale and I wanted to compare their frames against the ones I’ve been ordering from EyeBuyDirect and Zenni Optical. I’ll probably send the Zenni differentials back, but I will be able to use them for a bit before my new lenses arrive so I can compare.

While the new differentials reduce the correction in my dominant eye by 0.50 diopters of SPH (also trading -0.25 diopters of cyl from one eye to the other), the net effect is that my diopter gap is going to increase by 0.50 as well (increasing from a 1.63 to 2.13) which will make equalization a bit tougher when I start on that. I plan to remove cyl first, which will take the next 9-12 months or so. That will get me down to a 1.75 diopter gap and I’ll start working on equalization 6 months after that.

I wore the test frame with this correction for a while today while I was using the computer and it seemed pretty comfortable. As a test, I also tried adding -1.50 to the prescription to see how it does as full-strength glasses and I could read the 20/25 line with bifocal vision in poor artificial light. I’ll test again tomorrow during the day with natural light and I’m sure I’ll easily hit 20/20 in both eyes.

Now I just need to wait two weeks to try out the new lenses.

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