Cow Eye Dissection

Dissect a preserved cow eye to trace the path of light through cornea, pupil, lens, and vitreous to the retina, then identify the optic nerve, blind spot, and tapetum to connect structure with how vision works. Use the lens to form real images to demonstrate image formation and inversion.

• Follow instructions provided in the links below.

Cow's Eye Dissection - Exploratorium:

Cow's Eye Dissection - Biologybyme:

📄 The steps of a cow's eye dissection - Exploratorium: https://www.exploratorium.edu/explore/cow-eye

📄 Cow Eye Virtual Dissection - Biology Corner: https://www.biologycorner.com/worksheets/cow_eye_dissection_virtual.html

• Compare cow and human eyes using a model to discuss differences in eye muscles and presence of a tapetum.
• Shine a small flashlight on the posterior half to see how the tapetum reflects light back through the retina.
• Use a second lens or a magnifying glass to project a clear upside down image of a distant object onto white paper and relate focal length to image sharpness.
• Examine two eyes from different animals, if available, to compare retina color and tapetum size.

• Wear gloves and lab coat; avoid touching your face and wash hands after the lab.
• Handle scalpels and razors with care; make controlled cuts on the tray and cut away from fingers and body.
• Treat preservatives and tissues as potential irritants; work in a well ventilated space and clean spills promptly.
• Dispose of biological tissues, gloves, and sharps according to institutional and local regulations.
• Provide nitrile gloves for those with latex sensitivity; notify participants who are squeamish about dissections and offer an alternative activity.

• Why does an image formed by the eye’s lens appear upside down on the retina? (A convex lens focuses light so that rays cross at the focal plane, inverting the image.)
• What is the difference between aqueous humor and vitreous humor in location and function? (Aqueous fills the anterior chamber and maintains pressure and nutrient flow; vitreous fills the posterior chamber and supports the retina and eye shape.)
• What creates the blind spot in each eye? (The optic disc where ganglion cell axons exit to form the optic nerve has no photoreceptors.)
• Why do cows and cats have a reflective tapetum but humans do not? (The tapetum boosts sensitivity in low light by reflecting photons back through the retina; humans trade sensitivity for acuity and do not have a tapetum.)
• How many extraocular muscles move the human eye compared to the cow eye described here? (Humans have six; the cow example highlights four main movers.)
• What structures control how much light enters the eye and focusing of that light? (The iris controls pupil size and light entry; the cornea and lens bend light to focus an image on the retina.)