Someone who has vision in only one eye can no longer use as a cue for the perception of depth and distance.

Binocular cues--particularly retinal disparity and binocular convergence

Binocular cues are information (depth/distance) taken in by both eyes. The two main types of binocular cues are retinal disparity and binocular convergence. 

Retinal disparity arises from the fact that our left and our right eyes, being a few centimeters apart, view images at slightly different angles. The two different images are merged into one and this allows us to perceive depth in the things we see around us. 

Binocular convergence is the simultaneous inward movement of both eyes in order to maintain a single binocular vision. The closer the object is, the more inward rotation is required for the eyes. The degree of rotation of the eyes helps the brain to interpret the distance of the perceived objects.