The ability to judge the distance of an object is a crucial ability for our daily lives. Much of a person’s depth perception is thanks to stereopsis, the ability to take visual information from two eyes and sense depth. This two perspective method is used by 3-D cameras for filming movies and sporting events. But how does one see depth if they have only one eye?
The answer is they see depth by using pictorial cues similar to the ones used to look at a painting or a standard television. Size is a major cue. Things that are smaller are usually farther away. This concept is reinforced by the knowledge of how big an object, like a car, is supposed to be.
Linear perspective is an artistic concept that is also used in the real world by our minds – think railroad tracks going away from you. The closer you are to an object, its texture is easier to see. And if something is blocking your view, like the head of the person in front of you at the theater, you know they are closer to you than the screen is.
All of these cues are utilized to enhance, and in some cases replace stereopsis. The ability to use them develops at an early age and then develops further if you were unfortunate enough to lose sight in one of your eyes.
If you have a question concerning your eyes, ask Dr. Picken directly by emailing him at prairie firstname.lastname@example.org.
Dr. Jace Picken is an optometrist at Prairie Vision Center in Wahpeton