I've had bi-focals for a long time but never used them for tying. I always took my glasses off and leaned in close to the fly. I caught stray beard hairs in the fly a few times but had a great view of what I was doing. Even with the reading glasses I don't see the fly as well as I used to but it is acceptable. I haven't tried any real small flies yet, just a size 14 parachute adams and some bigger flies but I can see reasonable detail on small flies pulled from my boxes..