There's also the question of why would it experience horror? It's not exactly in pain, and they way they make the eyes grow is just to add the hormone signal that makes eyes grow when developing.
So from its perspective, it just got told to make eyes, so it has rudimentary eyes now. Hardly the most horrifying existence.
It's pretty difficult for it to go wrong in a way that isn't just nothing happening.
The eyes don't just grow randomly, you need to give the brain blob a chemical signal that grows eyes in-utero to make the eyes grow.