Of all the things that I've heard (and seen) brothers do, that has got to suck.

piss in his cereal

That is so evil :(
I can imagine the pain... my contact solution has peroxide in it x[ If you don't let it neutralize long enough: *tsizzzzzzz*

if i was you i would point a lightsaber laser at his eyes -_-..... just a thought.

Ehh, the OP is lying. I had vinegar put directly in my eye via eyedropper (my mom thought it was the eyedrops but had vinegar there because I used to get swimmer's ear), was forced to keep the vinegar in my eye for a minute or so, and it was perfectly fine once I rinsed it out. The only way it would still be burning (which really, it's more of a stinging) is if the OP kept doing this. Also, whiteboard cleaner is WAY worse.

The vinegar could've reacted with something in the contact solution to produce something that would burn.

Rub chillie all over his underpants every pair he ownes and wait for the screams

TOMAHAWK HIM!!!

42- OBVIOUSLY. wow.

If I were you I'd kick your brother square in the dick!

agreed. make him pay. every single day

Why the he'll did it take until the 2nd contact to realize it was vinegar?!?

Right on!

72- sometimes a contact stings your eye when you first put it in. Especially if you rub your eye wrong

Haha burnn :)

lol win!

Well, maybe you should think it's funny to put some IcyHot in his hand lotion.

WIN! Be sure to use the unscented kind or the gig will be up.

out of all the comments, I think this is totally the best option, op you really should do this. it will make his dick burn like he'll when he goes to jack off

Exactly what I was thinking!!!

I would do something bold and embarrasibg for everyone to see

Bold, why bold? Unusual choice there.
Unless you were talking strategies to deal with a bear attack of course...

I wonder if my reference is too subtle...
One hint: Doritos.

DORITOZ > FRUCKING EVERYTHING

what an ass...I agree with number 2

what a jerk! >.< fyl

ouch

make him pay
i'm talkin pain missery and embarrasement
hide waterproof video cameras in the shower take a video of him taking a shower then put it on the enternet

If you get kicked square in the dick it doesn't hurt as much as getting kicked straight to the balls