Hi coasty
I don’t think contact lenses will be the answer to your problem of near vision loss that is impeding your fly tying. Opticians will normally set the lens to accommodate a comfortable reading distance.
I read of a good tip by Alan Bithell for overcoming this particular problem that you are experiencing at the fly tying bench. Simple really, Alan suggested that one should visit an optician that is offering one of these deals where you pay for one pair of glasses, and get the second pair free. Have this second free pair made with your prescribed reading lenses set at a closer focal point than that, you read at. Have them made to accommodate the distance you normally find comfortable to
tie at. You should now have a pair of glasses that will be specifically made for your fly tying.
Perhaps if Alan sees this he will explain it all better.
Hope this helps
Midge