What happens when we look at shapes, try to find out how far away something is, notice movement and color? What is happening is that we are seeing. The eye is the organ that helps us to see, but the eye does not work on its own to make this happen.
| Parts of the Human Eye |
|---|
| Top lid |
| Eyelash |
| Pupil |
| Iris (eye-ris) |
| Bottom lid |
| Cornea |
| Tear duct |
| Sclera |
The eye is a ping pong shaped organ that works with the brain and with light in order to help us to see. The eye has three different layers, the outer layer, the middle layer and the inner layer. These three layers work with light to make us see the world around us.
Outer layer
In the outer layer, there is the sclera and the cornea. The middle eye consists of the ciliary body, the iris and the choroid and the inner eye contains the retina.
In order for us to be able to see, we must have light. When light goes on an object, the light is reflected and directed back to your eyes. Then, travelling through the pupil, the light passes through the lens. The lens is like the lens on a camera, it helps to make the image look clearer.
The lens turns the image upside down, or inverts it, and all of this happens without us knowing it. The image is then displayed in the retina and is inverted back upright because the rays are bent, and they cross each other.
The retina
The retina is a very important part of the eye. The retina is made up of tissues that have photoreceptors, also called optic nerves. These nerves help the body to detect light.
The optic nerve is responsible for taking the take the inverted image to the brain so that the brain can interpret the image and tell what the image is. This happens faster than you can blink. When the optic nerve inverts the image, this is called impulse.
The retina is made up of two different types of nerve cells called the rods and the cones. Rods are sensitive to the dark and they are responsible for helping us to see when it is dark outside or inside.
Cones are what helps us to see color. The cones are special cells that help us to see red, blue and yellow and then the cone nerve cells are able to change these three colors into hundreds and even millions of other colors. The cone nerve cells never stop working.
Facts about the eye:
- Each eye has around 120 million rods.
- Each eye has around 7 million cones.
- When the inverted image is focused behind or in front of the retina, farsightedness and nearsightedness can happen.
- Farsighted means that you can see objects far away but have a hard time seeing objects up close, this is also called hyperopia.
- Nearsighted means that you can see objects up close but have a hard time seeing objects far away, this is also called myopia.
- Wearing glasses most of the time can fix near and farsightedness.
- The nerves that are found in the eye connects to the occipital cortex that is located at the back of the brain.
- Our body uses muscles to adjust the lens to make images more clear.
- The Iris is the colored part of the eye.
- Muscles in the back of the eye help us to look left and right and up and down.
- The white of the eye is called the sclera.
- Conjunctiva is the surface part of the eye that is sensitive.
What Did You Learn?
- The eye is made up of how many sections? The eye is made up of three different parts, the outer layer, the middle layer, and the inner layer.
- How does the image come into the eye? The image that we see comes into the eye upside down. The image is then inverted and turned right side up with the help of other parts of the eye.
- What is the colored part of the eye called? The colored part of the eye is the iris.
- What are the three primary colors that the cones see? The cones initially see the three colors of red, blue and yellow.
- What helps our eyes to look around? Muscles that are connected to the eye help our eyes to look up, down, left and right.
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