While researching my next optic (Trijicon 3.5x35 variant) purchase the other day, I found a link to The Firearm Blog, with some good info pertaining to Red Dot, Holographic, and Prism optics. I thought I'd post it for your convenience. The More You Know: Living With Astigmatism When Using Red Dot, Holographic and Prismatic Optics - The Firearm Blog