I don't really understand having trouble with light when you sleep. Personally if I'm tired I happily sleep on summer noon with window opened. Just not in direct sunlight to avoid sunburn. And it's super pleasant experience for me. Better than regular sleep in the darkness at night.
Yeah this must be something that varies based on the person- I have some amazing sleep during daytime naps with sunlight streaming in. Consequently, I totally don't understand the fixation on blind openers, but I get that other people have different needs.
