Why do newborns sleep just fine with the lights on?!

Your baby's eyes are not very sensitive to light in the first month of life. In fact, the amount of light required for a 1-month-old infant to be aware that light is present (called the light detection threshold) is 50 times higher than that of an adult. So it's okay to leave some lights on in the nursery! It won't affect their ability to sleep, and it may help keep you from running into walls when you go in to check on them!