Here's a trick though. Have a gunsmith replace your rear sight with an old fashioned peep-sight with a wide shield. Forceing you to look through a small sight with a single eye seems to enhance your vision greatly. This trick was taught to me by my 90 year old grandfather (38 years in the Marines) who was still deadly with his piece when he died at 95.
Hey, thanks for that! I'll give it a try.