Introduction: (Initial Observation)
Eyes are among the most important body parts. Eyes provide us with the ability to see. A large amount of what we learn is by seeing.
We must protect our eyes from anything that may cause injury to our eyes or damage our vision. Learning about the eyes can help us to do this.
In this project you will make a 3D (3 dimensional) model of eye.
Note to parents: Some parts of the eye described in this project guide may exceed the curriculum of young students. You may skip some parts from your model. In general all models require Cornea, Iris, Lens and Retina.
Information Gathering:
Gather information about the parts of the eye and the role of each part in providing vision. Read books, magazines or ask professionals who might know in order to learn about the conditions, factors or activities that may hurt the eyes and our way of protecting our eyes. Keep track of where you got your information from.
Following are samples of information that you may find.
CORNEA
The cornea is a clear, curved membrane that covers the front of, and allows light into, the eye. It protects the pupil, the iris, and the inside of the eye from dust and other matter. The cornea helps to focus light onto the retina.
PUPIL
The pupil is a hole in the eye, covered by the cornea. Light enters the eye through the pupil. The amount of light that enters the eye is controlled by the muscles in the iris.
LENS
The lens is a clear, flexible membrane. It can change shape to bend the light that passes through it, focusing the light onto the retina and creating a sharp image.
IRIS
The pigmented (colored) iris is a muscular ring that surrounds and controls the size of the pupil. In dim light, the pupil is enlarged to allow more light into the eye. In bright light, the pupil is contracted to allow less light into the eye. Both actions are automatic, regulated by the reflex centers in the brain stem and spinal cord.
AQUEOUS HUMOR
The aqueous humor is a thin, watery fluid that fills the space between the cornea and the iris. It is produced by the ciliary body, which is just behind the iris. It provides nourishment to the front parts of the eye and gives it form and shape.
RETINA
The retina is innermost membrane of the eye. It is a network of photoreceptive (light-sensitive) nerve cells called rods and cones. The rods work in dim light and see primarily black and white. There are more rods than cones. The cones work best in bright light and see colors and fine details. The retina joins with the optic nerve and transmits the information received by the rods and cones to the brain.
OPTIC NERVE
The optic nerve connects the retina to the brain.
VITREOUS HUMOR
The vitreous humor is a clear, jelly-like substance that fills the central core of the eye. It helps the eye keep its round shape.
CHOROID
The choroid layer lies between the retina and sclera. It is composed of dense pigment and blood vessels that nourish the back of the eye. The choroid merges with the ciliary body and iris at the front of the eye, and is attached to edges of the optic nerve at the back of the eye. The iris, where it is not covered by the sclera, reveals the color of the choroid.
SCLERA
The sclera is the outer membrane of the eye. It encloses the entire eye, except for the part covered by the cornea. The muscles that move the eye are attached to the sclera.
Humans have white scleras that stand out from the face. This may be because we use our eyes to communicate. Other animals have scelras the same color as their irises. This keeps them from being seen by predators.
CILIARY BODY
The ciliary body forms from the choroid and merges with the iris. The muscles that change the shape of the lens are attached to the ciliary body.
Anatomy Of The Eye
The eye has been called the most complex organ in the human body as it has so many working parts. The ability so see is dependent on the actions of several structures in and around the eyeball.
The eye is like a camera. Light rays reflected from the object that you are looking at enter the eye through the cornea, which is like the camera’s aperture. The amount of light allowed in is controlled by the pupil which open and closes similar to the shutter of a camera. The light rays are bent, refracted and focused by by the cornea, lens and vitreous. The function of the lens is to make sure the rays come to a sharp focus on the retina. At the retina, light rays are converted electrical impulses which are transmitted to the brain through the optic nerve.
Other eye structures support the main activity of sight. Some carry fluids such as tears and blood, to lubricate or nourish the eye. Others are muscles which allow eye movement. Some protect the eye from possible injury such as the eye lids. And others, such as the optic nerve, are messengers sending sensory information to the brain.
How do you see?
Human eye works by allowing light to enter it and project onto a light-sensitive panel of cells known as the retina at the rear of the eye, where the light is detected and converted into electrical signals, which are then transmitted to the brain via the optic nerve.
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to construct a model of the eye and show main parts of the eye. Using your model or information that you gather answer the following question:
- Which parts of the eye are in risk of injury by external objects such as paper or pencil?
- Which part of the eye are in risk of injury by strong light such as sunlight?
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Identifying variables is not required for this project?
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
Having a hypothesis is not required for this project.
Following are sample hypothesis for the above questions:
- My hypothesis is that cornea is in risk of injury by external objects the most.
- My hypothesis is that Iris is in risk of injury by strong light. (Wrong!)
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Activity:
Make a model of the eye
Introduction: Model of the eye can be made with different material; however in all models you will need one lens. Remove the handle of any magnifying glass and use its lens.
Papers and paper towels can be made to use a model of the eye. The first part that you need to make is the Sclera or the white layer of the eyeball. Since you want to be able to see inside the eye, instead of making a full sphere, you will make a hemisphere to be half of the eyeball. This can be half of an actual plastic ball; but you can also make it using paper towels.
Here are the procedures:
Get a ball about about 4 inches (10 cm) in diameter. Place it on a cup and cover it with plastic food wraps.
Cut strips of paper towel about 1 inch (2cm) wide.
Make a solution of starch. Boil it for a few second and let it cool.
Insert strips of paper towel in the starch solution and place it on the ball.
Repeat this until multiple layers of paper towels cover the entire ball. Push the layers to remove any excess water. Let it dry in a warm place for about 24 hours.
Remove the dry hemisphere; cut any excess pieces; also cut a half circle on one side, where lens is being mounted.
Use hot melt glue or silicon glue to mount the lens.
Cut a circle from construction paper to form the iris. In the center of the iris remove a smaller circle to form pupil. Use glue to connect the iris over the lens. Make a hole in the back of the eyeball (opposite of the lens). A few strings of cotton (nerves) can enter from this hole and spread in the eyeball to form the retina. Label all the parts.
Using molding clays to make a model of the eye
Molding clays are available in different colors. Many of these clays are premixed with colors.
To make the eyeball white layer (Sclera), get a piece of white molding clay and use a roller to make it flat. This is like making bread.
Put the flat clay on a ball that is already covered with food wrapping or with some starch. The purpose of food wrapping and starch is to prevent the clay from sticking to the ball.
Using your hands form the clay over the ball. While it is still soft, cut and remove any excess clay hanging from the sides. What you need is just a hemisphere (half of a ball).
Leave the ball with clay on that in a warm place to dry. It may take about one day for the clay to dry.
Before the clay is fully dry, cut a half circle on one side. This is where the lens and iris will be installed.
Any plastic or glass magnifier can be used as the lens. For a 4″ ball, you should have a lens with diameter of about 2″.
Use some pink or red clay to attach the lens to the inside of the eyeball , where you cut a half a circle. If you don’t have pink or red molding clay, mix some white clay with red latex paint.
Use a spoon to level the edges of this clay. These must merge into the sclera. This pink clay represents the muscles that hold the lens.
To make an Iris, use the roller to flatten a piece of color clay. Then use a cup or bottle to cut a circle from that.
Use a smaller pipe or bottle to cut the pupil.
When the pupil is ready, place it on a ball and push it down so it will take the curve of the ball. This curve makes it easier for the iris to be mounted.
Use some glue to mount the iris on the outside of the ball, where it covers the lens.
Paint inside the ball with yellow color to represent the retina. Cover the iris with a clear plastic. This will be the cornea.
The hemisphere shown above was too thin and too fragile; so, it broke. That is why in the following instructions, we used clays with fiber to make it stronger.
Another step by step instructions
First we need a hemisphere (half of a ball). This hemisphere will represent half of an eye ball. This is called Sclera, the white area of the eye. Sclera encloses the entire eye, except for the part covered by the cornea.
To make this hemisphere, first place a real ball on the top of a cup and cover it with plastic food warping. Then get some molding clay and use a roller to make it flat. This is almost like preparing dough for making pizza.
The molding clay that I used in this picture comes ready made and it has some paper fiber inside. Fiber is what gives it some extra strength.
When the clay is flat, lift it and place it on the ball. then use your hands to form it like a hemisphere.
Make sure that the molding clay does not get very thin. A thin layer will break fast and you have to repeat everything again.
After forming the clay on the ball, cut any extra clay. Keep only half of a ball. Any extra clay will make it impossible for your dried hemisphere to separate from the ball.
In a warm place it will take about one day for your hemisphere to be dry.
Carefully lift and remove the dry hemisphere and if you feel that it still has some moisture, use a hair dryer to dry it.
One one side of the hemisphere cut a half a circle. The diameter of this half circle must be less than the lens that you are going to use. As shown in previous experiments, lens can be extracted from a magnifying glass.
Paint the hemisphere with white latex paint. Be generous in using paint. Paint will give additional strength to the hemisphere model and makes it easier to stick with other material that you are going to use later.
Get some elastic molding clay (without fiber) and mix it with red or pink color if needed. Cover half of the edges of the lens with this clay. This clay represents muscles that pull the lens when you try to see something really close.
Apply some wood glue on the clay and mount it where you just cut a half circle.
Use a spoon (wet if needed) to push the edges of the lens muscles until they get the same level as inside the eyeball.
Iris is made the same way it is shown on previous experiments. Put some molding clay on the inside edges of the iris, add some wood glue over that and stick it to the outside of the eyeball, right over the lens. There will remain a gap between the lens and the iris.
Let the whole thing dry overnight or at least for a few hours.
Make a small hole at the back of the eye where nerves will exit.
Get a yellow piece of molding clay. Use the roller to make it flat. Cut a half circle from that and place it inside the eyeball, opposite to the lens. This is retina, a layer of light sensitive nerve cells that eventually exit from the back of the eye.
Before mounting retina, you may need to apply some wood glue to the inside of the eye ball.
After you place the retina, you may use your wet finger to push down the inner edges so the retina will gradually disappear as it gets closer to the lens. You may use some extra yellow paint to paint some more retina closer to the lens.
Use a very fine brush and use red color to draw capillaries inside the eyes. Capillaries distribute nutrients and oxygen to the eyes. capillaries and nerves exit from the back of the eye. This can be displayed with additional stick of yellow molding clay that you may attach to the outside back of the eyeball (where you already made a hole).
When all this is ready, cut a round piece of clear plastic and place it over the iris. This is the cornea. Cornea actually is an extension of Sclera; however, it is clear.
Experiment 1:
Which parts of the eye are in risk of injury by external objects such as paper or pencil?
Procedure:
Throw a small object to the front of your eye model. Which part of your model will be hit by the object. What is it called?
Experiment 2:
Which part of the eye are in risk of injury by strong light such as sunlight?
Procedure:
Hold a large magnifier faced to the sun. Hold your hand or on the opposite side. Move your hand back and forth until a small image of the sun will form on your hand. This image is like the image that form on your retina when you look at the sun. What happens to your hand? Do you feel heat? Does it burn?
Materials and Equipment:
Materials used in constructing a model of eye may include:
- Small lens or magnifying glass (1″ to 2″ diameter)
- A plastic ball
- Molding clay (Ceramic clay may be used as well)
- Latex paints and small brushes
- Starch
- Wood glue
- Paper Towel
More complete list of materials can be extracted from the experiment section. Final list of materials may vary depending on the choices you make in constructing your model.
Make your own starch solution using Corn Starch
- Bring to boil 4 cups of water in a pot.
- With constant stirring, slowly pour two spoon starch into a beaker (or cup) containing (half cup) cold water to make a thin slurry.
- Slowly add the slurry to the boiling water. Allow the starch solution to return to a boil and continue boiling with constant stirring until all the starch has dissolved.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Calculations:
No calculation is required.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
References:
Search your local library and find books related to eyes. Information that you gather from books may help you to improve your model.
I wanted to share this great find with you. I found a great product on Amazon called Activa Rigid Wrap Plaster Cloth, 4-Inch by 180-Inch. You cut the product into strips and dip in them into warm water and apply it to a balloon blow to about 4”. When applied it makes a plaster like substance. I applied the wet wrap to half of a balloon( sitting in mug). When the product was dried I just pop the balloon and you have perfect and easy eye ball model shape. I left an area in the front shaped like a U where I applied the magnifying glass. I also found a fun way to make the capillaries inside the eyes I used frayed red thread and Elmer’s glue. I used a popsicle stick and push the yarn around with the wet glue . This made a very realistic looking capillary veins on the yellow modeling clay.
I hope you enjoy these new finds…
Sheri Gisser
