Out of all the five senses, your vision seems the most important. Humans are fairly unique in their reliance on sight as the dominant sense and this is reflected in how complicated our eyes are relative to other creatures.
Many animals gain most of their information about the environment through their sense of smell. Your dog’s nose tells him much more about his world and who is in it than his eyes (which can actually see some color). In contrast, you can’t smell all the wildlife that visited your yard but you could see them in vivid color.
How the Eye ‘Sees’
Why are human eyes so much more capable? Basically, it is because they have more components which collect information.
When you see something, like your pet dog, your eyes don’t actually see him, your brain does. At the start of what will become your vision, light enters your eyes. Your pupil, the black center of your eye, and the iris, the colored ring around it, work together to widen or constrict the pupils so the appropriate amount of light enters the eye.
The incoming light travels through two layers: the cornea and the lens. The cornea at the front of your eye, and the lens, located right behind your pupil, work in tandem to focus the light ray onto a specific spot at the back of your eye, on the retina.
At the retina is where the raw sight data your eyes collected from light begins to be translated into useful visual information. The light focused on the retina triggers photoreceptors which are used to create visual cues. The retina contains two types of photoreceptors: rods and cones. There are about 120 million rods and up to 7 million cones. Rods are more sensitive than cones but cannot detect color, which the cones can.
Humans have 3 types of cones which perceive the presence of red, green, and blue. These combine in different levels to create the full range of color we see. In case you’re wondering, your dog only has 2 of these, yellow and blue, which means his vision is closer to a human with red-green colorblindness than just black and white.
Now that information about the item and its color are collected, the rest of the work is left to the brain. This new data is sent along the optic nerve to the brain, which is what tells us what we are looking at. Along with what we are seeing, the brain sends information about the context: what does looking at this mean, is it dangerous, or other related memories.
Also your eyes and brain are constantly doing all of this. All in a tiny fraction of a second.
The Eye as a Sense Organ
The way sight works is why it is one of the five senses. The eyes are the physical portal through which data from your environment is collected and sent to your brain for processing. The brain plays its part by converting the light that went into your eyes into usable information — how far away, how bright, what color.
So if you were to look at your dog, you would see that, yes, it is a dog but also what breed he is and that he is your pet and would probably like his ears scratched.
Humans are built to collect information with their eyes and even reduced vision quality creates a negative effect. A regular vision test is a small investment for something that has such a huge impact on our lives.
Our eyes aren’t just performing a task, they are the portal through which our brain can tell us about our world, learn new things, and make wonderful memories. All of which are reasons why vision is such an important thing to take care of.