There are a couple of Optometrists that specialize in making glasses for shooters. They advertise heavily in the Trap and Skeet shooting magazines, like " Shotgun Sports". Allan Lehman, down in Arizona is one. They have websites, and 800 numbers. All you need to do is send them your eye prescription, which you obtain from your local Optometrist, and pick out the style of glasses you want. They will get the width of the frames from your prescription information, or may ask you to measure some existing frames.
What is unique about "shooting glasses" is that they move the focal point to the upper quadrant nearest your nose, to maximize the eye's ability to focus clearly on your front sight, or target. The Cost depends on what you order, and from whom, of course. They are not free. But, you can buy frames that allow you to change lens, so that you can used different colored lens for certain targets, or light conditions.
Are they worth it? Well, I bought a pair about 20 years ago, and my Average Score shooting Trap went up about 2-3 targets per hundred. Instead of breaking 23-24 targets per round of 25 targets, I began to break 24-25 targets. I thought it was worth it. I still have the glasses, and still use them shooting clay targets, with both modern and BP guns.