Reticle distortion is a reality due to design flaw - Vortex Defender-ST Enclosed Solar Micro 1x22.5mm Reflex Red Dot Sight

All of the negative comments you read on the Internet about the circle and circle dot reticles warping or distorting are true. The only spot in the glass that it doesn't distort is at the bottom of the center part of the glass - basically if you try to co-witness with iron sights, that is the ideal location to use the reticle. At any other place in the window, it will distort. I called Vortex and their customer service rep grabbed one off their inventory/shelf and observed the same distortion. It's not just at the extreme edges but all over the window. If you keep the reticle in the center of the glass it will be distorted. In the regular 3 MOA dot mode, the distortion is not noticeable but if you move your head around you can observe the dot following the curvature of the aspherical glass. I believe the issue is with how they placed the curve of the glass and the fact the emitter is aimed at the bottom center of the glass (where it appears the least distorted). Vortex said their optics department is aware of the complaints but as of now there are no plans to fix this issue and it is what it is.

I have plenty of Vortex products but I'd recommend either using it in the regular dot mode, or doing a hard pass on the Defender ST Enclosed until they figure it out.