I've passed the half-century mark, and I found out quickly that these old eyes couldn't see the white Glock sights. I put a dab of Dayglo-orange paint on them and now they are easily seen even in very dim conditions. They need a touch-up now and then, but for about $4 a bottle, you've got a lifetime supply.
If you prefer something other than orange, most drug stores carry nail polish in a host of bright colors that just happen to have a built-in applicator. They work best over a white basecoat.