Why does this kittens eyes look too big?

The eyes of kittens appear large because they are still growing and developing. The skull of a kitten is not fully formed, so the eyes are proportionally larger compared to the rest of the face. As the kitten grows older, the skull will grow and the eyes will appear to be more in proportion to the rest of the face.

In addition, kittens have larger pupils than adult cats. This is because kittens need more light to see well in low-light conditions. As the kitten grows older, the pupils will also become smaller.

These factors combine to give kittens their characteristic large-eyed appearance.