In my case, in last years my vision got deteriorated badly, (I'm 53 yo) not diabetic, 5'8", 169 lbs, run 3 mi twice a week at least, along with daily push up and sit ups (+/- 230), and karate classes. In other words, physically fit.
However, my eyes aren't following. I need scopes, some of my rifles have glass, some others not. M1-A doesn't, FAL will never, neither my surplus rifles.
The AR-15 has a red dot that by surprise help me in my AR carbine matches and I've got used to. Also I'm building other with larger barrel 20" to have a 1x4x20 mm or similar.
Nevertheless, always at the time of buying a new rifle, if it doesn't have an iron sights go to another brand.
Henry,
FL