How do you suddenly have astigmatism in both eyes? had bad reaction to topiramate about a month ago. related?

Puzzling: Topamax (topiramate) can cause swelling of the ciliary body in the eye which can cause the pressure to increase and to become very near-sighted. It is difficult to imagine a scenario in which it would cause or change astigmatism. These issues resolve with discontinuing the drug. Discuss this with your ophthalmologist.

Not related. : Most likely you have always had astigmatism, but it is manifesting or affecting your vision due to the aging eye not being able to compensate.