Spherical equivalent for cylinder causes hyperopic defocus?

My doctor fitted me with contacts that have no astigmatism correction in them. I’m not wearing the contacts on the weekend, or the bookends of the weekday, so I’d like to make things as easy as possible on my visual cortex by having 0 cylinder spherical normalized glasses instead of my ~1D cylinder aspherical grind glasses that give me a lot of vertigo. (In high school they told me my inner ear was defective. Oddly my inner ear works better when I have contacts on my eyes. Switching back and forth though causes more issues than wearing the glasses constantly.)

I have a test lens kit, but when I get into the range of that astigmatism adding more power doesn’t help my acuity enough to notice. I could use a Stenopeaic slit to find the ends of the volume of confusion and go for spherical equivalent in the middle, but wouldn’t that cause part of the image to be in hyperopic defocus? Is that going to slow my recovery down? Or does is it a neutral stimulus because there is hyperopic and myopic defocus at the same time?

I know tackling cylinder first is unusual, as is large drops in cylinder at once, but cylinder in contacts over -10D is hard to get. The doc is already unhappy with the lack of choices he has available with just spherical correction.

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Prior pondering that didn’t come to a conclusion:

I have wondered this too. Converting cyl to sph… especially in differentials… would that be counter productive? I guess it isn’t, since it is soemthing EM suggests, and I reckon Jake has thought this all through, but I would love more explanation so I can wrap my head around it.

Is your spherical negative? and are you adding positive cyl? Are you following the rule of adding -0.25 sph for every +0.5 cyl added?

Sphere is negative, not adding cylinder. My contacts don’t support cylinder, trying to match those to reduce vertigo when switching between contacts and glasses.

There’s no math involved in what I’ve done so far. I have a test lens kit. I was doing a spherical only trial refraction, and came up against a wall where I wasn’t improving acuity by adding sphere. I backed out the sphere to the last one that showed improvement, then added the stenopaeic slit, and I could see clearly. I could turn the slit 90 degrees and continue the refraction until it was clear again, or add cylinder at that angle, and then take the value halfway between, which is the basis of the spherical equivalent formula.