The horse has the largest eye of any land mammal. The lateral globe placement and horizontal ovoid pupil allow a total visual field of 350°. Narrow blind spots exist immediately in front of the nose and directly behind the hindquarters. Both eyes are used to look at a distant object until it comes within 1.0–1.3 metres (3–4 feet), which forces the horse to turn the head and look with only one eye. The mean refractive error is –1.0 dioptres (D).