Non-focusing sights are the ones that do not have that eye positioning limitation, but they also do not offer any magnification. These are non-magnifying sights that include various red-dot and holographic sights. There are a few 1x (unity magnification) focusing scopes out there that are usually identified as 1x prism sights. They have pretty flexible eye position requirements, but they are still not quite as lenient in that regard as true non-focusing sights. They do offer some significant advantages for people with astigmatism.