Most of us have a very basic understanding of how our eyes work, often taking our vision for granted. You would think that I personally would have a better knowledge of the eye, since I had terrible vision (I was actually considered legally blind without my contacts) until I had Lasik surgery twelve years ago. Even after that I hadn’t really thought much about how eyes work until Will’s diagnosis of Ocular Albinism in 2009.
Similar to how a camera works, the eye works by letting in light that bounces off of objects and focusing the light on the back of the eye or retina. The light enters the eye by passing through the cornea, which is a thin membrane on the outside of the eye, protecting the eye from outside objects. Next the light passes through the pupil which dilates bigger or smaller depending upon how bright it is. The darker the area, the larger the pupil is. The lens then focuses the light so that when it reaches the retina it is a sharply focused image. The lens flattens out to focus on far away objects and thickens to focus close. People who wear glasses and contacts need help focusing the lens correctly. As we get older, the lens hardens making it harder to focus on things up close (this is why it gets harder to read your prescription bottles and have to hold them father away to focus).
After passing through the clear fluid in the center of the eye called the vitreous gel, the light reaches the retina. Rods and cones on the retina turn the light into electrical signals and send those signals to the brain via the optic nerve. Cones are located in the central part of the retina called the macula. They are responsible for sharp detail and color. The rods are on the outside of the macula and provide the peripheral vision. The brain translates those electrical signals into the image we see.
The eyes work separately taking in the light and our brain creates what we see by putting the images from the eyes together. This allows us to have accurate vision of our three dimensional world. If you try covering one eye, you will notice how your field of vision changes and makes it more difficult to tell depth and dimension.
Hopefully this overview will help you understand how your eyes work and an appreciation of this complex and sophisticated visual system.
Photo credit – Baltimore Eye Care