Eye Dissection
Science 8
Mr. Shears
Names: __________________________
Date: __________________
Block: ____
Purpose:
The cow eye and human eye have many things in common. Examining a cow eye will help
guide the understanding of human vision.
How to Prepare:
2. Go to this website and watch the dissection video (about 8 min)
http://www.exploratorium.edu/learning_studio/cow_eye/index.html
3. Read through the instructions in the lab.
Materials:
1. Cow’s Eye
2. Scissors
3. Razor Blade
4. Dissection Tray
5. Protective Gloves
6. Paper towel
Safety:
The cow’s eye is raw meat. Make sure that you wash your hands at the beginning of the lab
and at the end of the lab to ensure that the bacteria is washed off. Keep your hands away
from your face during the dissection, this will decrease cross contamination. Ensure that your
animal parts are cleaned up quickly and efficiently after you have finished the dissection. Be
careful with the scissors and blades, they are sharp and can cut you. Most of all please treat
the animal parts with respect.
Procedure:
1. In partners, put on your gloves and obtain all of the above materials (except for cow eye)
and return to your work station.
Mr. Shears must sign before your proceed.
He will give you an eye when he signs off.
2. Look at the eye, it is protected by fat and muscle. The fat is a white tissue and the muscle
should appear pink.
a. Fat protects and cushions the eye.
b. The cow has four large muscles which help the eye move, where as humans have
six muscles which allow us to move our eyes.
3. Turn to the discussion questions, complete the diagram for #1
4. Use your scissors to trim away the excess fat and muscle around
the eye.
Mr. Shears must sign before your proceed.
5. Look at the front of the eye and note the outer layer, which is called the cornea. The
cornea is usually clear in the living eye, but may be cloudy in your lab eye. If you are
confused please see the diagram below:
6. Examine the rest of the eye. Note the sclera covers the eye. The sclera has a dark layer
that prevents the passage of light into the eye from the side. This keeps out stray light.
The optic nerve enters the eye at the back.
7. Use the blade to make an incision in the cornea. (Careful – Don’t cut yourself!) Cut until
the liquid under the cornea is release. That liquid is the aqueous humor. It is made mostly
of water and keeps the shape of the cornea.
8. Use the blade to make an incision through the sclera in the middle of the eye (halfway
between the cornea and the optic nerve). Some liquid will come out when you do this.
9. Use the scissors to cut the eye in half. Be very careful not to disturb the inner workings of
the eye as you cut. Separate the front half of the eye in the left side of your tray and the
back half in the right.
10. Turn to the discussion questions, complete the diagram for #2
11. The front half has the cornea. Cut the cornea with your blade. Listen for the crunch.
That is the sound of the blade crunching through layers of tissue – this tissue protects the
inner eye.
12. The next step is to pull out the iris. The iris is between the cornea and the lens. It may be
stuck to the cornea or it may have stayed with the back of the eye. Find the iris and pull it
out (it should come out in one piece). In a cow, the iris is oval, in humans it is circular.
The pupil is seen to be simply a hole in the iris. Set the iris and the cornea aside on your
tray.
13. Remove the lens from the eye. Using the paper towel wipe the jelly (vitreous humor) from
it.
14. Examine the lens, move the lens across these words. Then complete #5 in discussion
questions.
15. Examine the back half of the eye. Find the retina (it may not lay flat any more). The retina
will hang from the back of the eye at one spot. This is the blind spot. It is also where the
optic nerve comes into the eye.
16. The back of the eye may appear black or blue, the cow has this layer so that cow can see in
low-light conditions. Humans do not have this.
17. When you are finished the eye dissection and have found all the parts, call Mr. Shears over
and show him the different parts of the eye.
Mr. Shears will sign off when you have correctly identified all the parts in the eye.
18. Place the eye parts in the plastic disposal bag. Clean up all equipment and work areas with
soap and water. Remove your gloves and throw them in the garbage before going back
into the classroom.
Discussion Questions:
1. Draw a diagram of the eye before you dissect it, labeling all the visible parts
/5
2. Draw a diagram of the eye which is split in half and label all the visible parts
/5
3. List the differences between the cow eye and the human eye.
/3
4. Is the image that is cast on the retina at the back of the eye upright or upside down?
Explain your answer with a diagram.
/5
5. Describe the appearance, colour, shape, and feel of the lens from the cow eye. Did you
notice anything else?
/4
Conclusion:
Write a few sentences about what you learned in this lab:
/5