a) Define better. (Sharper, greater contrast range, better at spotting rapid motion, etc are some examples of parameters, but there's no reason to assume they'd all become 'better' by the same mechanism)
b) Melanin isn't conclusively tied to eyesight. If you search you'll find a lot of pseudo-science blogs but not much in the way of studies or even their abstracts.
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Watching liberals try to solve societal problems without a systemic critique/class consciousness is like watching someone in the dark try to flip on the light switch, but they keep turning on the garbage disposal instead.
戦争ではなく戦争と戦う