sunblock
NEVER goes above the eyes. Below the sun glasses and THAT’S IT. In kayaking classes about 1:25 folks discovered that and were VERY unhappy. They had to wipe their forehead clean and rinse eyes out with bottled water.
Expensive solution
I wear my Barz goggles when paddling. They have a rubber gasket that’s perforated to allow air to flow so they don’t get fogged. The eye balls are very happy, which is good, since I only have one pair of them.
Lou
lol
my eyes were giving me hell on a paddling/camping trip I took last weekend… No sunblok, polarized glasses and my cowboy hat…
have no idea what it was…?
wait… could’ve been those majic mushrooms I ate… yeah, thats prolly it 
Keep one eyeball in your pocket, so
if the other gets burny, you’ll be all set.
Sunblock
It happens to me if I get sunblock above the eyes. It has happened on fresh water so salt water is not the issue. You can avoid it by wearing a visor plus sunglasses so there is no need to put sunblock on the forehead.
Eyestrain from glaring sun/reflections is more of a fatigue and dryness/irritation sensation, not the intense stinging you get from sunblock in the eyes. If UV exposure is really strong, later on you feel like you have sand in the eyes. If this is what’s ailing you, get some sunglass lenses that allow less light to pass through. Around here I use Oakley’s “black Iridium” lenses for paddling–elsewhere I can get away with the normal gray lenses, or even none at all.
My Tilley is my forehead sunblock.
Very user friendly, effective, and sexy.
you might think
its the sunblock-although most folks don’t use the stuff on their foreheads…
Most likely it is the wind, drying out your eyes.
And the tear glands trying to keep up with that.
Sunglasses exaggerate the problem.
I use a small bottle with distilled water that I keep in my PFD to wet my eyes when that happens.