Horse’s eyesight is very effective at night because their eyes are covered by a special coating (the capetum lucidum), which acts as a mirror that reflects light rays, thus increasing the light available to the photoreceptors and improving vision in low light conditions.
With the aid of a partially illuminated night sky or starlit conditions, horses can perceive their surroundings as well as humans during a fully lighted day. Horses have the ability to see in low light conditions due to their unique eyes. Specifically, their large pupils and tapetum luc.
Horses possess a thin tissue layer located at the rear of their eyes known as the tapetum lucidum. This layer reflects light more effectively when compared to human eyes. Additionally, horses have a higher proportion of light-sensitive rods which determine color vision in humans. The presence of more rods and a tapetum lucidum in their eyes gives horses an edge in terms of night vision.