I was trying to shoot handguns with open sights the other day, and, yes, it's getting harder and harder. To the typical grandfather's presbyopia, toss in retinopathy and early cataracts and it's no wonder I don't see the both sights and the target clearly.
Like my friend, oneounceload, I do my shotgun shooting at clay targets. With the shotgun, I find it's best to generally ignore the sights -- I watch the target, not the sights. With experience and a proper fitting gun, you don't need sights, the gun will shoot where you are looking. This is where the term "seeing the lead" comes from. The sights on a target gun are there to verify that you have a proper mount. After I verify that the front and mid-rib rib beads form a figure 8, I don't look at them again.
As we age, the eyes are slower to change focus, so it makes sense not to ask them to do so. If your are constantly changing your focus from rear sight to front sight to target, your eyes are getting a work out. Once you verify that you're mounting your gun correctly, try to keep your eyes focused at the target. While shooting I try to avoid unnecessary close focusing. This includes re-loading by feel so I don't have to take my eyes away from target-distance focus.
Ilewis669, before you worry about getting a ghost ring set-up, make sure your gun is properly fit. You have to have total confidence in the fit and your mount to have the gun shoot where you are looking. There are several drills that can aid in your shooting. One that's common to shotguns and handguns is the blind mount: Pick a spot and focus on it, close your eyes, mount the gun and open your eyes -- the gun should be aimed at the spot.
Much of the gear we see marketed to shooters are gimmicks that attempt to let the shooter circumvent the need for a proper fit and adequate training. Unfortunately, if your work requires the use of armory guns, you may not be able to have a proper fit. There are tactical applications where ghost ring type sights are appropriate; but, they aren't used as a replacement for training.