Then it becomes a question of negligence-- in which case the reasonable person standard applies.
Did you owe a duty not to cum in the girls eye? Yes.
Was that duty breached? Yes.
Was the ejaculation the proximate and actual cause of her injury?
Can she show damages?
If you did it intentionally, she can sue-- unless you can make the argument that having sex with you in itself was a knowing assumption of risk on her part (which probably wont be a winning argument).
The real question is what woman would put on public record that she went blind because she was having sex with someone and then shot a load in her eye?