What is vision?
Vision is the process where your eyes and brain work together and use light reflecting off things around you to create the ability to see. It’s one of the five main senses and a key contributor to how most people understand the world around them.
How does vision work?
Vision starts when your eyes detect light and turn it into coded nerve signals, which then travel through your optic nerves to your brain. Your brain receives and decodes the signals, and turns them into the pictures you see.
Eyes
An easy analogy is to think of eyes like cameras, but it’s really the other way around. Cameras are an example of technology reverse-engineered from the human eye.
Cameras have lenses that focus light onto a special sensor inside the camera. That sensor converts light into electrical signals, and a special computer inside the camera translates those signals into the data that makes up the image file. You can also control the focus of a camera, and some cameras let you control how much light reaches the sensor.
Your eyes have lenses that focus light and direct it toward your retinas. Your retinas are like the sensor inside the camera, but far more sophisticated. They convert the light that lands on them into nerve signals and then send those signals to your brain. This happens dozens of times per second.
And the special capabilities of cameras, like focusing and light control, are also things your eyes do automatically. Your pupils can widen (dilate) or narrow (constrict) to control how much light enters your eyes. Muscles control your eyes’ lenses, changing how light rays come into focus for objects at varying distances.
Retinas
Your retinas are highly specialized, very sensitive cells called photoreceptors (meaning “light receivers”). When light hits them, it triggers chemical and electrical reactions in the cells. That’s how those cells convert light and encode them into nerve signals.
There are two main types of photoreceptors:
- Rods: These mainly detect differences in brightness. They help you see in dim or dark places.
- Cones: These photoreceptors are more sensitive. They can pick up more detail and detect different colors.
Once converted into coded nerve signal form, your retinas transmit the signals to your optic nerves.
Optic nerves
Your optic nerves are like data cables that link your retinas to various parts of your brain. The signals travel along the optic nerves to reach the various parts of your brain responsible for signal decoding and processing.
Brain
The last main step involves your brain. Your brain receives the coded signals carried along your optic nerves and decodes them. It then uses the decoded information to construct the “image” of what each eye sees.
Depending on what you see, your brain might have different areas working together to process and fully understand the picture. For example, reading a sentence like this also involves brain areas responsible for understanding language and recalling memories. That’s how you can understand the words, remember what they mean and use them to access related memories.
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What conditions could affect my vision?
Vision involves multiple body parts and structures working together, and different conditions can affect each. Some conditions can affect more than one part of your visual system.
Examples of conditions that can affect your vision, depending on the affected part, include:
