The overall ocular power of the pig’s eye has been calculated as 78 diopters . Pigs have wide angle of vision , thus, a panoramic view of their surroundings. Tanida et al. found that piglets have a tendency to move towards a more brightly illuminated area and respond negatively to the sharp contrast of black and white on the floor. Moreover, they suggested that a beam of light in the darkness could affect the movement of the piglets, even when it is directly in their eyes. This is not in agreement with Grandin (1982) who recommended that lamps should not shine directly into the eyes of the approaching livestock. However, Tanida et al. (1996) also recommended the light should be even and diffuse in order to encourage movement into poorly illuminated areas.