I’m getting to the point where it is difficult to thread the tippet. I don’t like bifocals on sunglasses but need some sort of visual enhancement to make tying on a new fly a less frustrating experience. What product recommendations are there from those with experience?
There’s a flip-down pair of magnifying lenses that clip to your sunglasses and you rotate them down over the glasses to see small things. They come in various diopters from 1.5 up to about 5.0 . Can’t recall the name; Flip-N-Focus or some such. They work very well ,but add weight to your glasses, but I think they’ll also attach to your hat brim. Never tried them that way.
Someone also makes flexible stick-on lenses. also in various powers, that you stick to your sunglasses. Like stick-on bifocals. You can remove them when you leave the water. They work well too, but lose their stickiness easily, esp if you get them dirty or dusty.
Other than that, carry a pair of Old Guys’ glasses in your vest.
One word of caution on the type that are supposed to clip to your glasses: I tried to go that route last year, but couldn’t find a pair that actually fit over the frame of my sunglasses. Like many of the fishing-oriented sunglasses, my Smith/Action Optics have plastic frames with a little bit of thickness to them, certainly more than the wire frames common to everyday eyeglasses or even aviators or other wireframe style sunglasses. What I discovered was that the bracket on the magnifiers that clamps over the tops of your glasses is not as wide as the plastic frames, so you get this awkward attachment where the magnifiers won’t fully seat themselves on the frame and ride up a little higher and certainly less secure than intended. I tried a couple versions of these, ranging from brands available in craft stores to the theoretically purpose-built ones available in some of the fly fishing catalogs, and the problem existed with all of them. The irony is that one of the more widely available brands of these, Flip 'n Focus, is made by Fisherman Eyewear, a manufacturer of many a line of plastic framed sunglasses for our sport. I called to ask them if I was missing something on getting these to fit or if there was a wider-bracketed model available and the young lady seemed somewhat surprised when she tried them on a pair of their own sunglasses and noticed the same thing. At some point I considered doing some alterations with a pair of needle nose pliers, but what you notice rather quickly is that almost all of these have brackets made of plastic. The F 'n F looked like it might be a coated wire bracket instead, but the lady I talked to wasn’t sure and I wasn’t willing to flush the 20 or 25 bucks to find out.
The flip down version are the best I have found. Yes, they will attach to the brim of a (baseball style) hat if the brim is not too long or your sunglasses. Lost a good pair when I did a nosedive running downstream trying to stop a steelie 
A buddy of mine uses the flip down type mounted on the bill of his baseball type hat. Heck, he uses them to read menus in cafes as well.
I tried a set of that type once, as as I saw it gently swinging back an forth to the bottom of the water, I gave up on wearing them. Then I went to the moisture stick on type, where you moisten the bifocal part and stick it to the bottom of your sunglasses. I used them for years and they worked good. But my eyes finally went down hill enough so I decided to just use regular glasses when I needed them. I keep an old pair attached to my shirt, or in a pocket and haul them out when I need them.
Larry —sagefisher—
Checkout the HatEyes by MagEyes. Now that I am in my 50s it has been a blessing. They come in varying powers.
Here is a link to the website. ClickHere
I use HatEyes and have been for years. Work very well for me.
If you’re like me, it only gets worse from here. Get a pair of readers from walgreens for about $10. Go to higher levels of magnification as you need it.
Or wear your regular bifocals and wear “cover ups” over them.
I wear bifocals on the stream, but it’s the size 20 midges that are a problem to thread. I bought the Hat-eyes and haven’t had any problems since then. They have certain adjustments that other flips don’t have and that IMO makes them better. They also swing out of the way when you don’t need them. The ony negative is you have to wear a baseball style hat, but that is what I usually wear anyways. I would definitely check them out.
Beaver
I bought the stick on readers for my Maui Jim shades last Spring & love 'em. I actually bought 3 pair thinking of loss, but the 1st pair are hanging tough after many cleanings & almost daily usage. This means I can spare one of my remaining pair. They are unopened OPTX 20/20 (+2.00) & if interested, I’ll ship for $10.00…price, as stated, includes shipping.
Mike