I'm not trying to scare anyone away from tuna, by all means consume it; I do, but I'm going to stop.
I'm no doctor and this is only a self diagnosis, so only take this with a grain of salt.

I've had perfect vision my whole life, and just recently I've developed very blurry vision, it onset very quickly! All this happened after I started eating 3 to 4 cans of chunk light tuna per day. One of the main symptoms of mercury poisoning is blurred vision. This is not necessarily what caused this, but I'm going to start consuming salmon and see if symptoms subside.

This not an anti-tuna preaching sermon, it's just my personal choice and I thought I would share it with you.
Any feed back is appreciated.