How Your Eyes Work
The eye is perhaps the body’s most delicate and complex organ outside the brain itself. It’s estimated that one half of the brain’s power is devoted to the vision process, which makes sense considering how important vision is to daily life.More importantly, your eyes are working constantly to process up to 36,000 bits of information every hour by your eyes. The human eye contains nearly 12 million photoreceptors which are responsible for interpreting and converting light into signals that give our brain the power to process vision, making the eye clearly a marvel of the natural world.
How Vision Works
While the eyes are incredibly complex, the basic mechanics of the eye can be understood by all. Your eyes are essentially a biological camera, which specialize in focusing light onto the photo-receptor cells in the back of the eye (also known as the Retina).The visible part of the eye is primarily responsible for regulating the volume of light that would be allowed into your eyes, which is important since the photoreceptor cells located on the retina (rods and cones) are highly sensitive. Once the retina receives the focused and accurate amount of light, photoreceptor cells change their shape via light sensitive proteins located in the cell membrane. When these cells change shape, nerve impulses are sent to the brain, allowing the brain to interpret these signals to decipher colors, light, and process the signals as vision.
Anatomy of the Eye
- Cornea: Clear cover over the Iris and Pupil, which allows light into the eyes. The cornea assists in focusing light as it enters the lens.
- Pupil: The black dot in the center of the eye, which filters how much light is allowed to enter the eye.
- Anterior Chamber: Chamber that sits between the iris and cornea, which holds liquid nourishment for the cornea and pupil.
- Iris: This is the colored part of the eye surrounding the pupil. The iris serves as a diaphragm to adjust the pupil’s size, which regulates how much light is received by the retina.
- Lens: Sits behind the cornea, iris, and pupil, and focuses light onto the retina in the inner-part of the eye.
- Sclera: The outer layer of the eyeball that appears white in coloration. The sclera gives the eye shape, and is essentially the eye’s shell.
- Conjunctiva: Mucous membrane that surrounds the exposed part of the eye and eyelid, and protects the eye from bacteria and environmental contaminants.
- Choroid: Thin layer of blood vessels that occupy the back of the eye and sit between the sclera and retina to provide nourishment to the eye.
- Hyeloid Canal: Canal that stretches through the center of the eye to transport fluid throughout.
- Retina: Membrane that sits on the back of an eye, and converts photons (light) into optical signals that the brain can read. Made up of rod and cone cells, which are specialized cells that receive and convert photons (light) into neurological signals to be carried to the brain for processing.
- Rods: Specialized cells located in the retina that are highly sensitive to light. Rods are used mainly for low-light vision, and aren’t as good at viewing color or fine detail as cones are.
- Cones: Specialized cells located in the retina that are sensitive to detail and color. Cones are used mostly for day-time vision, and are great at picking out colors and details.
- Macula: Center of the Retina that allows highly detailed vision.
- Fovea: Depression in the retina that contains no rods for acute eyesight.
- Vitreous Body: “center” part of the eye containing a clear gel like substance.
- Optic Nerve: The central nerve that connects the eye to the brain, carrying optical signals converted by the retina to the brain for processing.
- Optic Nerve Head: Location where the optic nerve enters the back of the eye, and where the eye’s blind spot is located.
- Ciliary Body: Sits adjacent to the lens, and is responsible for alteration in the convexity or concavity of the lens, while also produces nutrients needed for the eye.
- Optical Muscles: Responsible for eye movement and focusing on objects within viewing range. Most movement is involuntary, although movement can be consciously controlled.
- Eyelid: Protects the eye from harm, and spreads tears out across the eye when one blinks
- Eyelashes: Help protect foreign particles from entering the eye such as dust, allergens, and debris.