Sunnies
 

Flying the other day in marginal conditions - patches of low cloud and rain, plus a horrible haze that started low and just kept going. I had no idea where the cloud base was; viz just deteriorated as I climbed (the ground was of course always in sight if I looked straight down, but very indistinct). I was wearing clip-on sunglasses (these in fact: https://www.clipon-sunglasses.co.uk/...own-60-x-35-mm), When the viz got really dodgy, I tried flipping them up and was amazed at the difference. Without the sunglasses all I could see ahead was featureless white haze, even after waiting a few minutes for my eyes to accommodate. With them the cloud pattern was clear, I could see the darker nimbus clouds and rain and was able to drive around them.

Is this a known 'thing'? If so are all (non-polarising) sunglasses equivalent? These were cheapo flip-ups with a slightly dodgy flip mechanism but optically they worked amazingly well, I wonder if 'better' sunnies would have performed better? Until now I have not bothered to consistently wear sunglasses as they didn't seem to help much, I think I will change that. Any thoughts/comments from more experienced fliers?

Caruso make some excellent sunglasses

I use a pair of tinted varifocals as my 'spare pair' and they do seem to give a little better definition in marginal conditions, but not to the extent reported by DB. Sounds like you've hit the sweet spot with those, and a LOT cheaper than another pair of specs!
TOO

ps
Many years ago, a flying friend of mine was asked where his 'spare pair' were. He said 'oh, it's all right, I'm wearing them'. Nothing more was said...