Random thoughts on the eye as a target...
I've received a solid (accidental) eye poke in sparring 3 times.
One time I dropped to the ground clutching my eye in agony.
One time I stepped back and asked for a moment to make sure I was okay. I could have kept going, but wanted to make sure there was no serious damage for safety's sake. (For the next 6 months I would see occasional flashing circles of light when I was out at night.)
One time I kept going, got hold of my opponent, took him down and submitted him working by feel with one eye closed.
Based on this small sample I would say that targeting the eye is an effective tactic, but not a guaranteed fight finisher.
I practice a drill I learned from Roy Harris (JKD instructor, BJJ black belt) for setting up eye gouges, head butts, elbows, knees, and groin slaps off of pummeling for head control. It's semi free form, but not competitive. I like it because it works with a structure that I do practice in a resisted sparring context on a regular basis and just makes me aware of the opportunities for my opponent or myself to slip in those kinds of attacks without breaking our normal flow.
Given that we can't legally, morally, or practically practice eye gouges or pokes for real, we can never gain the technical mastery of them that we can with techniques such as chokes or punches. Nevertheless, they are effective enough and easy enough that it's worth not neglecting them entirely. Even if we don't want to use them, we should be aware of the possibility that someone could use them against us. I think a good compromise is to have awareness of how they fit into the other techniques that we can practice with more realism:
If I can hit you with a quick, accurate jab to your face (or even come up a couple inches short with my fist), then I might have been able to poke you in the eye. (Not guaranteed, but certainly worth considering.)
If I can't hit you in the face at all, or even come up a couple of inches short, then I could not have poked you in the eye.
If I can control you with grappling well enough that I can put my hand on your face and you can't block me or move your head away, then I could very likely have gouged you in the eye.
If an opponent can put his hand on my face at all, then the chances of him being able to attack my eyes are non-zero, even if he doesn't have full head control.
Conclusion: if I want to be able to target the eye effectively or prevent someone from targeting my eyes, then I should practice being able to hit an opponent without being hit and being able to control him in grappling range so that I can reach his face and he can't reach mine.
BTW - just because you don't incorporate these techniques (or any other) into your regular sparring doesn't mean you can't be aware of them. Even when I'm grappling with no strikes I like to keep a little subroutine going in my head that notes "he could have hit me with an elbow there, his hands were in place to poke me in the eye, I was open for a head butt, etc" and adjust my body to prevent those opportunities as much as possible even though those techniques aren't allowed in practice and my sparring partner has no intention of using them.