If it's truly bad enough, like others have said an etched reticle can be a great option. Depending on your budget, try and look through some of the higher end optics - Elcan, Acog etc... the clarity of image and reticle is absolutely fantastic for those with an astigmatism etc. The Elcan has the advantage of being a true 1X, and Also 4X. The Acog - if you can shoot with both eyes open, the BAC (Bindon Aiming Concept) is fantastic as well. I also shoot with an Aimpoint Comp M4 with glasses/astigmatism, and with a reasonable brightness the star-burst is very manageable.