Why some people have smaller/narrower eyes and other have larger/wider eyes, both Caucasian?

Is it genetics, is it more common in the British Isles and similar ancestries or the Balkans. I have notice there's Caucasian people with narrow eyes, usually dark coloured or light coloured but small eyes, and others like more Italian wide eyes shape. As best I can describe. On either gender. Why or how? Has anyone else noticed but me?

As you can see, I'm Caucasian and wide eyed. Blue.

Why some people have smaller/narrower eyes and other have larger/wider eyes, both Caucasian?
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