Written by Prof. Kent Caslow, Elia’s Professional Director
3D vision
Three-dimensional vision is built on the difference in the point of view of the two eyes, one to the right of the nose and the other to the left. When we look at two objects and their figures form equal angles in both eyes, we see each of the objects once, without a three-dimensional diagnosis.
This situation mainly occurs when the objects are on the imaginary circle line formed when the angle in the two poor is equal.
All the points on the contour of the circle form an equal angle in both eyes.
If the objects we are looking at create different angles in both eyes but with small differences, we will interpret this visual event as three-dimensional.
If the objects form large angle differences between the two poor we will see one of the objects double (twice).
Three-dimensional vision depends on the existence and cooperation of both eyes and therefore does not occur in situations where there is monocular vision or squinting.
Within a range of up to 1-2 m from us three-dimensional vision is very useful in estimating depth and distance, beyond this range the angle between the two eyes is small and estimating the depth and distance estimate due to angle differences is ineffective.
Depth Vision
Depth vision is the ability to distinguish objects located at different distances from each other, beyond a range of 2 meters. When we are mostly dependent on one-eyed signs we learn (empirically) to see depth. These signs are processed and learned throughout our lives by the brain, through vis-motor experiences.
The following is a list and examples of some of these signs:
- Lighting Perspective :
Since lighting almost always comes from above, we learn about depth by distinguishing between an illuminated area versus a shaded area. If we rotate the page the depth in the images is reversed.
- overlap:
Objects that overlap with each other signify to us that the hiding object is closer (before) the hidden.
- Relative size:
We learn to compare size to distance, larger objects are interpreted as closer.
Here is an example of how you can easily “cheat” the brain:
- Linear Perspective:
Parallel lines appear to connect to a distant point on the horizon.
- Parallax:
When we are in motion, close objects move faster and against the direction of our movement, distant objects move more slowly and with the direction of our movement.
- Atmospheric Perspective:
The farther we look the more the atmosphere blurs the image and we realize that these objects are farther away.
In conclusion,
Although both three-dimensional vision and depth diagnosis are learned vision skills, there is no doubt that one-eyed signs (depth diagnosis) are much more dependent on visual learning throughout our lives and require more visual-motor experiences over time in the child’s development. Therefore, for children with visual impairments with much less random visual learning from the environment, more difficulties in this area are expected. There is no doubt that this can affect mobility and orientation.
