@SeeTheLight, a typical highly myopic eye, as well as corrective aid to fully correct it, have ±0.25 D measurement/power error.
Some more expensive lenses, as well as cheapest China 1.5 super-thick lenses, have 0.25 steps after ±6 D. But the most lens brands in optics shop near me have only 0.5 increments.
So, I would vote for 0.5 reduction until 6 D.
@Dlskidmore, I tagged you because there is a person that actually decreased his axial length by 0.07 mm in 4 months, and it’s pretty close to what Jake says, despite this person encountered too few progress compared to others on this forum. He has moderate myopia, though. You should not be too pessimistic…
Also, you can search on this forum about 95 years old testimonial of -20 and -3 cylinder myope reversed his myopia to about -3.5.
Some studies suggest that eyes with high myopia elongate way more doing accommodated near work than eyes with lower myopia. Let’s hope we can reduce high myopia faster, too.
You actually have about -13.5 myopia (about 4 diopters more than I have), because that’s a madness to calculate true myopia value with vertex distance compensation in such high ranges. You don’t have astigmatism as well. Any astigmatism with “wandering axis” generally doesn’t count as and should not be corrected, as it’s transient.
If you have esophoria, i.e. your eye(-s) have a tendency to look at each other when you’re tired, find a good gaze fixing exercises or go for orthoptic training. Because there’s a book on this forum with a study linked that eyes with esophoria have significantly faster myopia progression than eyes with exophoria. It should help reducing any astigmatism to a minimum, too.