Although it dates from 2006, I have found this review on astigmatism clear and useful.
I remember a while back reading somewhere that the visual cortex has an easier time accommodating mirror image astigmatism than parallel astigmatism. I have not been able to find this again. If anyone else has picked up on this, please let me know. I have oblique mirror image astigmatism and find that my visual cortex doesn’t have too much trouble balancing this out in uncorrected vision. I had hoped to find something in this review, but no luck.
Edit: Alas, I seem to have found something that seems to falsify my hypothesis rather than confirm it. But as this is in induced astigmatism it may not count as much. I have had many years of neural adaptation to my uncorrected astigmatism. This is from another review of astigmatism.
Measures of stereoacuity are also reduced by monocular and binocular induced astigmatism, with the most pronounced effects found for induced binocular orthogonal oblique astigmatism (i.e. axis 45° in one eye and axis 135° in the fellow eye).106