eye disorders
Other Eye Symptoms
Impaired Depth Perception
Depth perception is the ability to determine the relative position of objects in space. People with impaired depth perception may have difficulty distinguishing which of 2 objects is closer. The retina is the light-sensing structure at the back of the eye. It is a 2-dimensional surface like a piece of film in a camera and can only produce a 2-dimensional image. The brain integrates the 2-dimensional images from each eye to create a sense of 3 dimensions (stereopsis). Stereopsis allows people intuitively to perceive depth. Disorders in which the eyes do not align properly (such as Strabismus ) can interfere with stereopsis. However, stereopsis is effective only in a close range, such as within arm's reach. If objects are farther away than about 9 feet (3 meters), clues to depth perception obtained from only one eye (for example, the apparent size of objects) provide more information on relative position than stereopsis. Thus, a person who sees with only one eye will have trouble pouring a cup of tea but will have less trouble parking a car. 