When you look directly at a bright light, why does it “stain” (for lack of a better term) your vision when you look away?

Question

When you look directly at a bright light, why does it “stain” (for lack of a better term) your vision when you look away?

In: Biology

Answer 1

Bleached photo pigment.

When you light enters your eye. It is absorbed by a chemical (photopigment) and changes shape. When enough pigments change shape, it sends an electrical signal to your brain. This signal tells you there is light. These pigments are constantly changing shape (upon the detection of light) and being reverted back to their original shape so they can again absorb light again. When you stare at a bright light source, you’re bleaching or changing more photopigment than that part of your eye can regenerate. This results in an afterimage. Most people take approx 10 mins to regenerate that photopigment. This is also the reason why it takes around 10 mins to adapt to a dark room.