His eyes are wide open when he looks like that, they have no eyelids and that’s how they control the amount of light they let in. His eyes get like that because you’re exciting his feed response. Someone else might be able to explain it more “elegantly”, but yes and it happens to almost all snakes that I know of. It can help determine the mood and actions of the snake also. If the eyes look like a fine hair, they’re relaxed or possibly sleeping. Eyes almost completely black, they are definitely paying attention. Hope this helps.
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