Hi Andrew – yes I have had plenty of personal experience with this!
It hits me most when the following is true:
* I practice in the afternoon/evening (but it does happen from morning classes too)
* The room is VERY humid and a lot of sweat is happening
* I am in the first few classes “back” after a break
I have come to do a couple of things to help:
Firstly I believe in my case it is both acclimation and acclimatization and after 10 or so classes in a short period (eg 10 days) it does reduce dramatically, though extreme humidity/heat combination can bring it back
Secondly, I usually wash my eyes (just bathe in clean water) a few times during the day/night after class and this helps a lot
I can tell if I am likely to be afflicted just by the way my eyes feel after class – and so I get straight onto gentle bathing.
Finally, make sure your hydration is thorough and you are getting plenty of salt replenishment, especially if you are a “salty-sweater”!
I hope that helps and good luck with your challenge, let us know how you get on!