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DISSECTION OF THE COW EYE
Please make sure to wear gloves and safety glasses
when you are dissecting, and make sure to clean up
thoroughly after the lab. Also, the cow eyes can be
rather slippery, so use caution when handling and
cutting them. You will need a scalpel and forceps.
1. First, identify the most external structures of the
eye. Near the posterior pole, observe the optic
nerve, which was obviously cut when the eye was
removed. Additionally, you should be able to see a
large mass of tissue attaching to the periphery of
the eyeball. This tissue includes the extraocular
fat and possibly several of the extraocular
muscles. You do not need to identify individual
muscles, but try to distinguish them from the fat.
The most external layer of the wall of the eyeball is called the fibrous layer. It is a dense,
avascular connective tissue that contains the contents of the eyeball. The posterior 90% of the
fibrous layer is the opaque sclera. The anterior 10% covers the anterior pole of the eye and is
called the cornea. Since light must pass through it, it is translucent.
Once you have identified all of these structures, remove the extraocular fat and muscles from
the eyeball.
2. Place the eyeball on the dissecting tray and gently hold it with two fingers at the cornea and
the optic nerve. Cut a cross-section through the sclera slightly behind the middle of the
eyeball so that the eyeball is separated into an anterior half and a posterior half. Only cut
through the wall of the eyeball, not through the entire globe.
The inside of the eyeball is filled with the gelatinous vitreous humor, if you cut too deep
into the globe, this may start
leaking out, which is not a
problem. Once you have cut
around the entire periphery of
the eyeball, separate into two
halves. Let the vitreous humor
slide out of the eye. You may
need to gently tease it loose
from the inside of the eye.
3. The eyeball should now be
separated into an anterior and
a posterior half. Turn the
anterior portion of the eyeball
over on the dissecting tray so
External view of the cow eye
