Late to the party, but I find that blocking the sun with the edge of the helmet, a cycling cap bill or even a hand is at least as important as glasses in sun-shade-sun-shade scenarios. If your helmet has a visor, that can help a lot. Having crashed by hitting a small log because of this scenario (it was juuuuust inside a dark patch and I never saw it), I understand how important dealing with this can be.

And FWIW, I do not ride without a helmet. Full stop. My brain is the only one I've got or will ever have.

Friction shifting or indexed?

I have SportRx lenses with their “start-to-finish” flavor. They describe them as rose copper tint with a light mirror finish.

I use them on trails: shade, shade mix, full sun. Also on the road when I’ll be finishing around dusk. They increase contrast and strike a nice balance.

For midday with full sun on my face, I have a darker set of lenses. I wouldn’t want to fly down a dark shaded trail or get caught with the sun going down with those darker lenses.

A visor that keeps the sun off the lenses makes a big difference in going from shade to sun, IME.

I wonder if those yellow glare-cutting lenses would do anything...?

Slightly OT, but what bike lights are you using? Traffic behind you has the same problem. I find it here on older country roads with mature tree cover. And. of course, those are just the type of roads a driver might expect to be nearly traffic free, and thus be less vigilant.

Welding helmet, of course. Instant on/off.

Not particularly in my experience. I often ride with some amber sunglasses that block everything south about 490 nm and they are still a problem in an abrupt dark/light transition. About the only helpful thing I've found is to shift my glasses forward a bit on my nose and tip my head down and look over them when I hit the shadow.

That all depends on if you have an accurate pressure gauge.

^^^^^^^^^^
This.

Use glasses with one dark lens and one clear lens. When in the sun, close the eye behind the clear lens, as you enter a dark area, open the eye behind the clear lens and close the one behind the dark lens. Alternately you can leave the eye behind the dark lens open, since that won't affect you much.

I ride with an older pair of prescriptions glasses. I haven't worn sunglasses on the bike in 25 years, but when I did, I got cheap flip-ups. At speed they flip up and against the helmet. If they break...they were cheap.

I do have a pair of those big over-your-regular-glasses sunglasses for the car...but I rarely wear those anymore either.

I got interested in old, manual focus, manual exposure cameras 30 years ago and I stopped wearing sunglasses to get a feel for the brightness of my surroundings. After a while I realized I didn't really need them anymore except driving into the sun.

Photochromic lenses are way too slow to lighten up, as others have commented. They work great for rides after sunset, where they have time to adapt to the dimming light.

A 600+ lumen headlight would work great. Turn it on when you reach the woods.
I don't notice a problem with shaded paved roads, even with the trees completely arching over the road, so I don't need a headlight for that. Instead, it's on a short, sharp flash mode, to instantly catch the attention of oncoming drivers. It's flashing whenever I'm riding on roads. On bike trails, my Cygolite has a separate set of 4 small LEDS that can be set to flash by themselves -- this is perfect for dark bike trails, to be seen far away, but not annoy oncoming riders and walkers. Or aim the light downward.

Remember Blue-blockers? The miracle ‘sunglasses’.

I had a pair of cycling glasses, which I unfortunately cannot remember, that had graduated levels of shading. Dark on the top, medium dark in the middle and light at the bottom. All I had to do was tilt my head in changing light. “Why don’t all sunglasses mfgs offer these?” :D

A lot do. I have a pair of Raybans that are like that. You simply have to look for them.

The terminology gets mixed with photochromatic. Search for "gradient" sunglasses, they're still made.

Have an old pair of Vaurnet ski glasses with lighter tint through the middle third. Great for bright days cycling but too dark for wintertime unless it's fully sunny, given they're intended for sun and snow.

Are they the mirrored ones with blue frames with the red, white and blue inserts around the rims? I had a pair of those in the 70s.

I never mentioned terminology, though I knew the correct term. There are many gradient lens sunglasses available. I have never heard anyone call them photochromic.

Not too high tech but I've been pushing the glasses down to the bridge of my nose when entering the thickest parts of the trail.

The Prizm Trail arrive tomorrow so well see how that goes.

Instant Dimming sun glasses are out there. Some of the ChiCom instant dimming Welding glasses can be had for as little a 5.00 USD. The instant dimming dimming sun glasses are still very pricey...

https://ashchromics.com/

https://www.wicue.com/products/eyewear

I guess the solution was right there under on your nose the whole time.

Very cool. Did not know this existed

After trying several lenses I’m going with Prizm Trail Torch. They are decent in bright sun and offer clarity in the forest trails Slightly darker than I would like but best I’ve found and I tried several.


https://cimg0.ibsrv.net/gimg/bikefor...57a55283f.jpeg

My main gripe is the mirror finish and funky tint give them an 80’s WWF vibe.

I don't use sunglasses when cycling. I wear my normal glasses and wear a helmet with a visor to help keep direct sun out of my eyes. I also tend to ride on trails with a decent amount of shade this time of year. Winter is harder as the leaves drop and the sun is lower. By the way, eyeglasses do a decent job of blocking UV and don't dilate your pupils.

Otto