What is depth perception?
Depth perception (also called stereopsis) is the ability to perceive the world in three dimensions. Depth perception allows for accurate estimations of distance and an accurate spatial map of our environment.
How do we see in 3d?
Because of the spacing of the eyes, each eye collects a sightly different picture of the surroundings. The brain then puts these two pictures together in a process called “fusion” where one image is made. The differences in the pictures allow for three dimensional vision.
Depth perception should be well developed by the age of 2. Since depth perception demands binocular vision, getting an eye exam as recommended will insure that normal development is not delayed. Conditions like strabismus (eye turn), or anisometropia (a different refractive error in each eye greater than one diopter), or other problems can cause an eye to be suppressed causing a condition called amblyopia where there is poor binocular vision and therefore poor depth perception. Only an ophthalmologist or optometrist would find these problems.
Assessing depth perception
A simple tool called the Randot Stereo Test may be used in the optometry office as a quick measure of depth perception. A test involving lining up two sticks at a distance called the Howard-Dolman test is also a way to assess depth perception. Assessing depth assessment could be helpful as reduced stereopsis was found to be common in older patients with falls (1) along with reduced acuity. Again, the necessity for eye exams can not be overstated for al populations.
Monocular Depth Perception
What if there is only vision in one eye? The brain will learn monocular cues for depth that will allow for the person to safely function, drive and even play sports. Brains are amazing!!
(1)Källstrand-Eriksson, J., Hildingh, C., & Bengtsson, B. (2016, July 11). History of falling and visual ability among independently living elderly in Sweden. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/27468223