The cornea bends the light before it passes through a watery substance that fills the area behind the cornea, called the aqueous humor. The light continues to travel through the black opening in the center of the iris, called the pupil. The iris is the colorful part of your eye that gives it its blue, green, hazel, brown or dark appearance. The iris is actually made up of muscles that expand and contract to control the pupil and adjust its size.
So when you see your pupil getting bigger or smaller, it is really the iris that is controlling the pupil opening in response to the intensity of light entering the eye. The light passes through the pupil to the lens behind it. The lens adjusts its shape to bend and focus the light a second time, to ensure that you have a clear image of what you are looking at. At this point, the light has been bent twice— as it moved from the cornea through the lens, and then from the lens to the retina.
If you suspect you have blurry vision or an eye condition, contact an eye doctor near you, who can diagnose and treat the condition. The light then passes from the lens to the back of the eye which is filled with a clear, gelatinous substance called the vitreous until it reaches the retina , the light-sensitive layer at the back of the eye.
The light is then focused throughout the retina which contains nerves called photoreceptors. The photoreceptors are made up of rods and cones, and are responsible for transforming the light rays into electrical impulses. While the light is focused throughout the retina, most of the light entering the eye is focused onto the focal point on the retina, known as the macula.
Once the image is clearly focused on the sensitive part of the retina, energy in the light that makes up that image creates an electrical signal. Nerve impulses can then carry information about that image to the brain through the optic nerve. Other parts of the eye include the aqueous humour , a liquid which sits in a chamber behind the cornea, and the vitreous humour , the clear gel that fills the space between the lens and the retina.
The sclera is the white part of the eye, forming an outer layer that protects everything inside, while the choroid is the layer of the eye that lies between the retina and the sclera. It is made up of layers of blood vessels that nourish the back of the eye.
Refractive errors are eye disorders caused by irregularity in the shape of the eye. This makes it difficult for the eyes to focus images clearly, and vision can become blurred and impaired.
Short sight myopia and long sight hypermetropia are common conditions, both caused by the cornea and lens not focusing properly on the retina. Short sight is where the eyeball is elongated or the lens is too thick, causing the image to focus in front of the retina. Long sight is where the eyeball is too short or the lens too thin, causing the image to focus behind the retina. Prescription glasses can help with both long and short sightedness.
When light stimulates the nerve cells in the retina, messages are sent along the optic nerve to the brain. The optic nerves from the two eyes join inside the brain.
The brain uses information from each optic nerve to combine the vision from the two eyes allowing you to see one image. How your eyes work PDF. How your eyes work RTF. Skip to content. Each human retina and you have two, one in each eye contains million rods and about 6 million cones. This is 70 percent of all the sensory receptors in your entire body — for touch, taste smell, hearing and sight all put together.
Each rod or cone cell at the back of the eye has a stack of discs inside, The discs contain a pigment molecule. Rods and cones each have a different opsin.
Cones have a pigment-protein pair called photopsin Foh-TOP-sin. It comes in three different types, and each cone has just one type. They come in red, green or blue — the colors that each cone type is best at absorbing. Cones respond to light that has passed through the lens and onto the fovea. As each cone absorbs its color of light, it produces an electrical signal. These signals travel to the brain, filling our worlds with color.
In September , a vision researcher at the University of Washington in Seattle discovered some cones also sense white light. But only white light. That was a big surprise, Ramkumar Sabesan said at the time. In fact, he and his colleagues found, so-called red and green cone cells each come in two types. One transmits white light, the other relays color. Especially surprising, most of these cones are the white type. Out of red cones tested, signaled white. Of 98 green cones tested, 77 reported white light.
White-sensing cells also detect black which is the absence of white.
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