Your eyelids aren't the last line of defense against light — your retina still picks up on it. Here's why even a "dark enough" room can quietly disrupt your sleep, and what an actual zero-pressure blackout mask changes.

It's not lack of sleep — the skin under your eyes is up to five times thinner, with almost no fat layer to protect it. Here's what's actually happening, and the 15-minute ritual that targets it.