Of course, you can. Now, almost all eyeglasses frames are available for prescription lenses including vintage cat eye glasses. Besides, you don't need to ask an optometrist replace the lenses with my prescription, i believe that most optical glasses shops ( both online and local shop ) are willing to fill your vintage cat eye glasses with prescription lenses. If i were you, i prefer to get such glasses online because they are much cheaper.
Maybe. Generally speaking, you can have your cat eye glasses fitted with prescription lenses. But it depends where you go. Some optical stores are unable to replace the lenses with prescritpion ones. If you do want to have them replaced, you should take your cat eye glasses back to your optometrist. He or she will know whether you can have your lenses replaced or not. If you can't, you'd better get a new one.
Sure, you can get your vintage cat eye glasses fitted with prescription lenses. If you want to get a pair of prescription eyeglasses with vintage cat eye style, you can ask optician to fit your vintage cat eye glasses with prescription lenses when you buy it. If you have vintage cat eye glasses frames by hand, you can also ask optician or optometrist to install your vintage cat eye glasses.