First, this isn't about vision problems that require glasses. It's about the value of wearing glasses even if you don't need them.
I've thought about this for a number of years as several incidents have happened and each time I thought, this wouldn't have happened if I'd been wearing glasses. E.g. I was out walking and the wind blew something significant in one of my eyes. It stopped me in my tracks while I tried to carefully resolve the problem.
In my younger years, I've had numerous bugs hit me in the eye while jogging. I've had twigs come near hitting me in the eye while walking in wooded areas.
But more to the point, are glasses an asset or a liability in a gunfight? IMO, they are an asset all the way. The main consideration is this. When we go to the range to shoot/train or to a school to train, we always wear glasses. Why? Obviously to protect our eyes from any debris that might come our way from shooting.
Then should we be wearing glasses if we were shooting in a gunfight? What happens if we're practicing and something hits our eye? We stop shooting, and respond according to the severity of the injury. What if something hits our eye, either as a result of shot debris or even wind blown debris, in a real gunfight? We just might die!
So am I suggesting that we wear glasses all the time? No, certainly not - I'm saying we should wear glasses only when we think we may have to fire our gun in self-defense. It's kinda like only carrying your gun when you think you'll need it isn't it?
I'm at a point where my vision is slightly farsighted and I can see quite well without glasses, just not up close. Being farsighted, I've found that I can buy inexpensive, low power (1x or 1.25x), full size lens reading glasses and I can see just as well in the distance and better at arm's length - about where my sights would be.
I find that I'm wearing my glasses (reading glasses that I really don't need, at least yet anyway) more and more. Not to see better per se, but for the protection they provide. Not only do they help protect against wind blown debris, they do the same thing in a gunfight that the do on the range - protect the eyes. It'd be a pretty awful moment if an eye was injured in a gunfight. That could easily decide the outcome.