Just for the record - I'm a grappler and I have practiced dealing with eye pokes. (Both deliberate simulated eye pokes for training purposes and accidental real ones) I've also practiced delivering them.
Eye pokes, groin shots, throat grabs, etc are all valid techniques, but they are secondary to having solid delivery mechanisms. Once you are on the ground, the person who can control the position is going to have a huge advantage in both delivering and defending against such "dirty fighting" methods. If you are on the ground with a grappler and can't stop him from mounting you, then your attempts at poking his eyes are likely to provoke a (much more effective) retaliation in kind from on top.
(I won't get into the discussion of takedown defense, since my takedowns are pretty mediocre at best.)