The walls of the top level of the underground silo are covered with large screens showing the outside world. The images are captured by cameras above ground, and the camera lenses get grimy with dirt that is only cleaned off when an expelled resident of the silo cleans the lenses with a pad of wool before walking off to their death.
While in the holding cell before leaving the silo, Holston notices dead pixels on the screen, and imagines a future where most of the pixels will be dead. These screens are the residents' only images of the outside world, apart from drawings and photos in old children's books from long ago, and so he imagines that the few remaining true pixels in the future might be taken for the ones that are broken.
Holston has recently found the documents that caused his wife to believe that the world outside is in fact not toxic, and that the images on the screens are fake. This scene not only expresses his own distrust in the technologically mediated view of the outside world, it also explores how human interpretation of technology can also be flawed - hundreds of years later, when nobody remembered how the technology was supposed to work, how would people know what was a true pixel and what was a broken one?Â