Natural daylight exposure in childhood promotes healthy eye development, reducing the risk of myopia. Bright light matters for kids' vision and sunnies are shitcoins.
Discussion
I thought the research only showed a correlation with being outdoors, not the light brightness? That said, I spent plenty time outdoors as a kid and became myopic before I got my first computer (let alone sunglasses).
Clearly other factors involved but bright sunshine exposure in youth seems to confer benefits.