[Gavin Stevenson]

Had excellent days fishing on Lake of mentieth yesterday however this morning I woke up to a pounding headache across my eyes and the last time I had this type of headache I had also been fishing. Common issues were long drive +2hrs each way to fishing and full day on water, I was wearing sunglasses all day

Anyone had same experience and potential root cause

[Keith Potter]

Used to have something very similar and eventually came down to dehydration. Not drinking enough water during the day always gives me sore heads as if someone is stabbing right through my eyes with a nail.

Could it be eyesight related?

[Mike Barrio]

I used to suffer from them years ago.

Some possible causes:
Eye strain. I think this was almost certainly the cause of mine, early stages of needing glasses.
Bad posture, tension of back & neck muscles, especially when constantly balancing yourself boat fishing.
Dehydration, less likely perhaps if you normally take plenty to drink with you, but also worth weighing up if it's enough.
I would have included the sun, but you said you were wearing sunglasses all day.

I'm no doctor, but these things come to mind.

[James Laraway]

I wonder if it's the sunglasses arms squeezing on your head? Just a thought

[Sandy Nelson]

I wonder if it's the sunglasses arms squeezing on your head? Just a thought

Thats not a bad shout really. I've got rid of a couple of glasses because they were too tight to my face and pushing against my temples, especially with retainers.
I suffer really badly from Heatstroke and when its sunny I have hats, buffs, specs and tonnes of water (I bought a filter bottle so I can drink from the river)
I know a peak hat makes a big difference for me as do proper polaroids, normal sunglasses don't remove the glare as well as polaroids.
Lots to consider