Probably not, because that most likely means I will have to extend to reach their head. Extending is rarely "a sound tactic" because it leaves you open and vulnerable.
If their head is already within reach, and my life is in danger, I will probably go for the eyes.
I absolutely believe a good slash across the forehead could blind an attacker, but even aside from the risk of over-extending, I don't believe there will be enough blood to instantly blind an attacker, nor do I believe there will be enough continuous blood to leave them blinded for long.
What I do believe is inflicting damage on a deadly opponent without taking any is a sound tactic, and I also believe blinding an opponent for even an instant is good, because that in turn gives me a little more time to inflict even more damage, so that I can hopefully escape, or if that seems unlikely, inflict even more damage until the threat has been neutralized.
So...slash across the head of a deadly threat? Sure, I'd do that, if I could do it without opening myself up, and didn't have a better target, but if my life or the lives of others is on the line, I plan on cutting whatever bits an attacker is foolish enough to dangle in front of me, until I can disengage with honor.
John