In the dark people experience a total absence of vision, there are several degrees of darkness where people can have a limited vision, distinguish figures or objects, or flat see absolutely nothing.

The human being from the beginning of time has avoided being in total darkness, not only for fear of it, but also for security measures. Hundreds of years ago the human being took refuge in caves or sometimes slept in the open air, in both cases he used to sleep near a bonfire, not only because of the heat offered by the fire, but also to have a field of vision of its environment to be forewarned against the attack of nocturnal predators.

Technology and science advances every day surprising us, there is a project currently developed since 2015, where it is intended to implant night vision or ability to see in the dark in the human eye through an injection of a substance applied directly to the eye , although it seems incredible this study has been tested in humans, this liquid is known as "Chlorine 6", the most notable is its application in the conjunctival sac of the eye to facilitate night vision, although studies are being conducted is not a treatment that is available in the market for the general public.

Formerly also people used a kind of night vision, which consisted in adapting the eye to the dark, the merchant sailors of antiquity used a patch that covered only one eye, this in order to accustom the retina of that eye to the darkness, in this way when they went down to the ships' cellars they did not have to carry candles for security measures, they only had to change the eye by discovering the eye that had been covered, since the retina was adapted to the darkness, it made it easier for the sailor to distinguish the objects in the darkness.

Cats are domestic animals that have been endowed by nature with more acute senses than humans, one of these senses is sight, a more outstanding difference is their field of vision, while human beings have a field of 180 degree vision the cat has a visual field of 200 degrees. Cats have excellent vision in low light, at night their vision is amplified 6 to 8 times more, being able to see much better at night compared to humans who do it during the day. The human being has the ability to adapt his vision to the dark, but always his visual field will be very limited having to depend on the darkness of his other senses as touch with his hands to touch and recognize objects in the dark.