On top of the old age stuff, I've had a number of eye issues, including retinal detachments and, now am developing cataracts. I don't typically wear glasses, having one eye that is near-sighted and one that is far-sighted. But I'd gotten so that the front sight was blurry. I did learn instinct shooting for close range stuff (<10 yds) and used a Laserlyte target system for fun.
I did some handgun silhouette shooting years ago, and found a Merit optical attachment to be really helpful. The suction cup sticks on your shooting glasses or other glasses. It pivots out of the way when you need it too. Of course, a piece of tape with a hole in it would work too, as other people have noted above. I recently put the Merit V.I.A on my AR-15 recently. It's a replacement for the standard AR rear sight in the carry handle.
All that being said, I did go to my optometrist with my pistol slide and had her give me a prescription for shooting. It works well in my ESS ICE Naro glasses, and I use it for general target shooting - pistol or rifle.