I have the old...astigmatism also, and have various red dot sights on my powder and air guns.
The Holosun line of red dot's is one favorite. For my amount of bad vision, the Holosun produces a fairly clean dot/circle. The key...is not to turn the volume (brightness) up too loud. Keep it as low as possible and still be able to see the dot/circle. Works well for me.
Holosun has a verity of different sights. Red, green, amber (gold). Most are adjustable with just the dot, just the circle, or both the dot and circle. Smaller versions for pistols and larger versions for rifles. I have a pistol sized sight on one of my Bullpup air rifles.
I have others also. Might be large, but no larger that a scope, the Vortex, Strikefire, has a very clean / sharp red dot, even with my crappy sight.
Mike