Shooters reaching age 40 and over tend to express some concern regarding blurred sights. Having experienced similar problems, I would like to share with you my experiences and solutions. The technical information I will give you should not to be taken as accurate medical advice but used only as a guide to possibly help you and your Opthamologist or Optometrist develop a solution to your particular situation.
After extensive and successful cataract surgery I found that although I had excellent vision, when I held up my musket, the sight was extremely blurry. The Carbine was even worse and the pistol was impossible. I visited my regular eye Doctor, an old friend of mine, who said he would try to help and offered some suggestions. With his permission I brought my musket into his office after hours and while I sighted, he would hold lenses up in front of my new glasses. We found that when he reduced the power of my new glasses with his test lenses, the front sight was much clearer. He then loaned me a test device that would attach to my glasses and allow me to slide in various test lenses. Each lens would allow me to add or subtract diopters from ¼ to ¾ at a time. With my new found eye testing equipment, I went home and set it up on my shooting bench with my musket.
To further explain the problem, consider the following. An eye with a natural lens can focus on the front sight and the target at the same time. The natural lens expands and contracts to focus the image. The same thing occurs with a scope. You focus the lens by adjusting it to your eye but you must keep readjusting it as the range changes. After 40 years of age, much focusing ability is lost to the average person. By age 60, it is mostly gone, but there is always SOMETHING there. With a plastic lens, it is ALL gone, and it is just like a scope. You can set it up for a particular range but must change it for different ranges. The Opthomologist tries to find a happy medium for good vision but is not concerned about sights and targets. An older shooter with a natural lens and a shooter with a plastic lens (catarct replacement) are in somewhat the same position. They can see the target clearly but the front sight is blurry.
Now back to my testing. I put up a target and donned my equipment. When I started changing test lenses, I found that when I wanted the front sight clearer in my farsighted right eye, I would increase the power of the test lens. (Note- for a farsighted eye, to make the sight sharper, you increase the power of your glasses by the test lens. This will slightly compromise the target. For a nearsighted eye, you decrease the power of your glasses by the test lens and the target is again slightly compromised.) I found that when I weakened my farsighted eye (by increasing the power) by ¼ of a diopter, I could see the front sight clearly and the target well enough to hit it. This was for the musket with its longer sight radius. The carbine and revolver presented another problem. With the carbines shorter sight radius, I had to go ½ of a diopter to see the front sight but the target was much more blurred. However, it was possible to shoot. Not very good but possible.
The revolver was the worst. With its extremely short sight radius, I had to go to ¾ of a diopter to see the front sight clearly. Fortunately, The target was only 25yds. away and I could get by, but it was never really clear. The Model One Maynard with its longer sight radius and tang sight really opened up the Carbine to me. The sights are really clear (tang sight) and I can compete with my musket glasses. At one time, I had musket , carbine and revolver glasses. Now I only have musket and revolver glasses.
My testing revealed another amazing phenomenon, astigmatism. The Eye Doctor showed me the correct setting for my particular astigmatism but when I turned the setting from one extreme to another, I could bend the front sight left and right but it would look just fine. This would explain how different shooters could shoot the same gun with different impact points. One more thing about my revolver. My right eye is my natural shooting eye with the revolver. I have never had the clear sight I wanted but took what I could get. Last winter, I discovered that without glasses, my left eye was almost as clear as my right eye with glasses. Some testing later, I developed a shooting lens for my left eye that is very good. It took some getting used to, (shooting with my left eye) but my performance seems much better this year.
So how can this be of any help to you? Possibly by weakening your lens, the front sight might become more visible to you. What I would suggest for a place to start is the following: Take a measurement from the front of your glasses to the rear of the front sight of the gun you want to use. Then take a ¾ by ¾ pine stick and cut it a few inches longer than your sight measurement. Properly place a finishing nail in the correct position to simulate your musket or carbine sight measurement. The measurement from your glasses to the rear of the front sight should match the stick measurement from your glasses to the rear of the nail. The nail should be slightly shaped to look somewhat a front sight. If your Eye Doctor will cooperate, take the stick with you when you see him. When you are set up with your proper eye prescription with his testing equipment, place the stick up in front of your shooting eye and sight it at the eye chart. (This will take a little fiddling) Have him drop different lenses in place and see if he can clear up the front sight and still be able to read the chart. Dont go for 20/20 but try for 20/30 or even 20/40. If you can see the front sight, the center of a blurred or clear target is still the center.
See if he will give you a prescription to take to one of the cheap lens makers (K Mart, Lens Crafters possibly) to have lens made for you. This is cheaper and much quicker than most Eye Doctors and it can be made in a few hours. It may take a few lenses to test because only the Range can show you what you can really see. This just might work for you. I have an extensive collection of rejected lenses but that was the price I had to pay to see and still shoot competatively. I sincerely hope that some of the above may be helpful to you.