system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When looking straight at a light, why does the shape of it stay in your vision?
gpt
When we see light, it enters through the pupil and shines onto the retina, the light-sensitive lining at the back of our  eyes. If a bright light shines on the retina long enough, the part of the retina it’s hitting becomes somewhat desensitized to light, so when we look away, the desensitized part doesn’t immediately respond to the new input it’s receiving. This causes us to perceive a negative space in our field of vision that’s in the shape of the bright thing we were just looking at until the affected part of the retina becomes sensitive to light again.