Explanation
How horses see and the role of movement
The lateral position of horses’ eyes gives them a wide field of view, but leaves small blind spots that can be compensated for by moving the head. Their vision combines monocular and binocular fields, and the retina enables them to detect movement.
Wide vision, with eyes on the sides
A horse’s eyes are located on either side of its head. This position gives it a panoramic field of view, suited to perceiving what is happening around it. Because the eyes move very little within their sockets, the horse turns its head to direct its gaze towards something that interests it.
Seeing with one eye or both
The horse combines monocular vision—with one eye on each side—with binocular vision in front of the muzzle and towards the ground. When it holds its head still, it has small blind spots just in front of its nose and behind its tail; a slight movement of the head can compensate for them. Binocular vision enables depth perception and three-dimensional vision.
What enables movement detection
In the retina, rods contribute to visual sensitivity and enable movement detection; cones are involved in visual acuity, that is, the perception of details and colours. This describes the functions of visual cells; on its own, it does not predict how a particular horse will react to a moving object.
The field of view also depends on posture
The position of the head and neck can alter the field of view. The IFCE technical source notes that postures with the nose behind the vertical can restrict it, and that the restriction increases the more extreme the posture. Therefore, the field of view is not an isolated anatomical characteristic: it also depends on how the horse is positioned.
Sources
- The horse's vision - équipédia - IFCE · equipedia.ifce.fr