We received a question from one of our ForeseeHome patients as to why the horizontal lines in the test are presented clearer than the vertical lines. The answer is that they are not presented differently; each line is presented with the same intensity and contrast regardless of orientation.
There are several reasons why we might perceive horizontal lines differently than vertical lines.
The anatomical reason is that the cells, called neurons, in the portion of our brain referred to as the visual cortex (where images from our eyes are processed) are more tuned to horizontal rather than vertical images. In addition, the density of cones (cells responsible for color vision and sharp vision) is higher along the horizontal than vertical meridian in the central area of vision and therefore our visual discrimination is better along the horizontal than vertical meridian. Lastly, the way light is focused in the eye to form an image in the retina, may play a role.
The reasons for asymmetry are not clearly understood, but it may be that our world is oriented more horizontally than vertically. Generally, we move our head horizontally then vertically, and most writing systems are either left to right or right to left. Essentially, we process information more horizontally than vertically, and the brain seems to have been designed or has adapted accordingly.
Looking at optical illusions may highlight how we perceive horizontal and vertical lines differently.
Here the vertical line appears to be longer than the than the horizontal line, but in fact, they are both the same length.
Our brains and visual system are wonderfully made to allow us to see the world around us. Let’s do all we can to keep them working well. ForeseeHome is here to help preserve your vision so that you can continue to enjoy seeing the world oriented in all directions.
