Difficulty shooting with both eyes open using SPARC AR

Not sure if this is the best place to post this but I don't post in r/guns so figured I'd post here. I have fairly bad astigmatism but found that if I focus on a target that I can use the red dot somewhat easily. What I want to know is if my astigmatism is causing the double vision when keeping both eyes open?

Would it be better keeping both eyes open with a higher quality rds? If so I could probably save up for it because I already have a strike eagle for my mid length ar, and was really just wanting a rds for when I start a pistol build.