Sparkling Eyes

In manga and anime, sometimes eyes are drawn sparkling, typically with four-pointed stars drawn in the iris, or the pupil being replaced by four-pointed star that spans the whole iris.

When this happens, it's generally because the character is captivated by something. They saw something they want, something wonderful that they like, or something amazing. They have become filled with excitement, desire, ambition, and so on.

Left: Enshuu Ritsu 円修律
Right: Akutagawa Taketo 芥川丈途
Anime: R-15, Aaru Juugo あーるじゅうご (Episode 1)

In Japanese

The word for the act of sparkling in Japanese would be:

kirakira
キラキラ
*sparkle* (mimetic word.)

Okumura Rin 奥村燐, example of sparkling eyes.

Character: Okumura Rin 奥村燐
Anime: Ao no Exorcist, 青の祓魔師 (Episode 17)

me ga kagayaku
目が輝く
[Someone's] eyes shine.

Often, but not always, sparkling eyes are drawn with one four-pointed star spanning across the entire iris. In this case, it's specifically called:

juuji-me
十字目
Cross-shaped eye.
- Literally "十 character eye," because the juu 十 character looks like a cross.
shiitake-me
しいたけ目
Shiitake eyes. (because shiitake mushrooms are often decorated with cross-shaped cuts when used in cooking.)

Doma Umaru 土間うまる, example of me ga shiitake 目がしいたけ, "the eyes are shiitake mushrooms." The second image is altered with real mushrooms.

Character: Doma Umaru 土間うまる
Anime: Himouto! Umaru-chan 干物妹！うまるちゃん (Episode 2)

Some anime use five-pointed star eyes instead.

Tsukino Usagi 月野うさぎ, example of star eyes.

Character: Tsukino Usagi 月野うさぎ
Anime: Bishoujo Senshi Sailor Moon, 美少女戦士セーラームーン (Episode 1)

me ga hoshi ni naru
目が星になる
[Someone's] eyes become stars.
me ni hoshi ga aru
目に星がある
There are stars in [someone's] eyes.

Lastly, when eyes shine brightly and strongly, with a huge sparkle covering the whole eye, that's typically because the character has set their eyes on something, like a predator setting eyes on a prey and ready to attack.