Depth 1
What blind people actually see
When people lose their sight completely, they usually do not see blackness, because black is still a color you need working eyes to perceive. Instead, try closing just one eye and see what it perceives. Nothing, right? Not even darkness. That is what total blindness feels like. Yet, amazingly, many people who are legally blind can still sense light. Deep inside our eyes, special cells called intrinsically photosensitive retinal ganglion cells contain a protein named melanopsin. These cells do not help you read a book or see the color blue, but they tell your brain whether it is daytime or nighttime.