When we say a person has blue eyes, we really mean the person has blue irises! The iris has muscles attached to it that change its shape. This allows the iris to control how much light goes through the pupil say: PYOO-pul.
The pupil is the black circle in the center of the iris, which is really an opening in the iris, and it lets light enter the eye. To see how this works, use a small flashlight to see how your eyes or a friend's eyes respond to changes in brightness.
The pupils will get smaller when the light shines near them and they'll open wider when the light is gone. The anterior say: AN-teer-ee-ur chamber is the space between the cornea and the iris. This space is filled with a special transparent fluid that nourishes the eye and keeps it healthy.
These next parts are really cool, but you can't see them with just your own eyes! Doctors use special microscopes to look at these inner parts of the eye, such as the lens. After light enters the pupil, it hits the lens. The lens sits behind the iris and is clear and colorless. The lens' job is to focus light rays on the back of the eyeball — a part called the retina say: RET-i-nuh.
The lens works much like the lens of a movie projector at the movies. Next time you sit in the dark theater, look behind you at the stream of light coming from the projection booth. This light goes through a powerful lens, which is focusing the images onto the screen, so you can see the movie clearly.
In the eye's case, however, the film screen is your retina. Your retina is in the very back of the eye. It holds millions of cells that are sensitive to light. The retina takes the light the eye receives and changes it into nerve signals so the brain can understand what the eye is seeing.
The lens is suspended in the eye by a bunch of fibers. These fibers are attached to a muscle called the ciliary say: SIL-ee-air-ee body. It has the amazing job of changing the shape of the lens. That's right — the lens actually changes shape right inside your eye! Try looking away from your computer and focusing on something way across the room. Even though you didn't feel a thing, the shape of your lenses changed. When you look at things up close, the lens becomes thicker to focus the correct image onto the retina.
When you look at things far away, the lens becomes thinner. The cornea and aqueous humor form an outer lens that refracts bends light on its way into the eye. This is where most of the eye's focusing work is done. The colored circular membrane in the eye just behind the cornea is called the iris.
The iris controls the amount of light entering the eye through the pupil, which is the opening in the center of the iris that looks like a tiny black circle. Like a camera, which controls the amount of light coming in to prevent both overexposure and underexposure, the iris becomes wider and narrower, changing the size of the pupil to control the amount of light entering the eye.
The pupil gets bigger when more light is needed to see better and smaller when there's plenty of light. The eye's lens sits just behind the iris. Just like a camera lens, the eye's lens focuses light to form sharp, clear images. Light that has been focused through the cornea and aqueous humor hits the lens, which then focuses it further, sending the light rays through the vitreous humor and onto the retina.
To focus on objects clearly at varying distances, the eye's lens needs to change shape. The ciliary SIL-ee-air-ee body contains the muscular structure in the eye that changes the shape of the eye's lens. In people who have normal vision, the ciliary body flattens the lens enough to bring objects into focus at a distance of 20 feet or more.
To see closer objects, this muscle contracts to thicken the lens. Young children can see objects at very close range; many people over 45 have to hold objects farther and farther away to see them clearly. This is because the lens becomes less elastic with age. The retina the soft, light-sensitive layer of tissue that lines the back of the eyeball wall is made up of millions of light receptors called rods and cones.
Rods are much more sensitive to light than cones. Each eye has about million rods that help us see in dim light and detect shades of gray, but they cannot distinguish colors. In comparison, the 6 million cones in each eye allow us to see in bright light and they also sense color and detail. The macula MAK-yuh-luh is a small, specialized area on the retina that helps the eyes see fine details when we look directly at an object.
It contains mainly cones and few rods. When focused light is projected onto the retina, it stimulates the rods and cones. Skip to main content. How Do We See? Sight is one of our most complex senses. But have you ever stopped to wonder just how eyes work?
The process of human vision is pretty amazing. Parts of the eye—the exterior Our eyes are organs, just like our heart, kidneys, and our skin our largest organ. These include external structures like: Your eyelids, which offer protection for your eyes.
The tear film, which carries oxygen to the cornea and helps keep your eyes healthy and comfortable. The eye interior The main interior structures of your eyes include: The iris, which is the colored part of your eye. The pupil, the black circular opening in the center of the iris that lets in light. The crystalline lens, suspended behind the iris, which allows you to focus on near and far objects. The retina, which is a very thin layer of millions of photoreceptors called "rods and cones.
Our vision system is efficiently designed indeed. Nothing in this article is to be construed as medical advice, nor is it intended to replace the recommendations of a medical professional. The eye is enclosed by a tough white sac, the sclera.
The cornea is the transparent window in this white sac which allows the objects you are looking at to be carried in the form of light waves into the interior of the eye. The surface of the cornea is where light begins its journey into the eye. Because it is out front, like the windshield of an automobile, it is subject to considerable abuse from the outside world.
The cornea is masterfully engineered so that only the most expensive manmade lenses can match its precision. The smoothness and shape of the cornea, as well as its transparency, is vitally important to the proper functioning of the eye. If either the surface smoothness or the clarity of the cornea suffers, vision will be disrupted.
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