Biology 11–12 · Year 12

Cow's eye dissection: the structures that focus light and the site of visual disorders

Module 8: Non-infectious Disease and Disorders (Technologies and Disorders: visual disorders)

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

The cornea and lens together bend light onto the retina, so their shape and clarity decide whether an image is sharp, which is why spectacles, contact lenses and laser surgery act on the path of light through the front of the eye.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

Sharp scalpels and blades
Bacteria on raw animal tissue
Fluid squirting when the cornea is cut
Distress at dissection

Controls

Cut away from the body on a board; carry blades on a tray
Gloves for anyone with cuts; wash hands thoroughly; disinfect surfaces; never store tissue in a food refrigerator
Eye protection when cutting the cornea
Offer an alternative task to anyone who opts out

Note

The eyes are bought from a butcher or an abattoir, fresh on the day; disinfectant per RiskAssess (https://www.riskassess.com.au/). NSW permits the dissection of animal parts bought from a butcher, supermarket or abattoir, no learner can be compelled to dissect, and any other source needs Schools Animal Care and Ethics Committee approval (https://education.nsw.gov.au/teaching-and-learning/animals-in-schools/animals-in-schools-issues/dissection-of-animals); the Department's Animals in Schools framework sets out the school's wider obligations (https://education.nsw.gov.au/teaching-and-learning/animals-in-schools).

What you need

One cow's eye per two learners, from a butcher or abattoir, ideally with muscle and fat attached and bought on the day of dissection (the source advice)
Scalpel or single-edged blade and scissors per pair; cutting board; wax paper; paper towels; newspaper page for viewing print through the lens
Gloves for anyone with cuts; disinfectant; plastic waste bag; soap and water

How to do it

Identify the sclera, the fat and muscle, the cornea and, through the cornea, the iris and pupil; trim away the fat and muscle.
Make a small cut in the cornea to release the aqueous humour, then cut through the sclera around the middle of the eye to separate front and back halves.
Remove the cornea and cut it on the board to feel its layered toughness; lift out the iris and note the pupil opening.
Remove the lens from the vitreous humour, feel its soft outside and firm centre, and place it on newspaper print to see the print magnified.
Examine the back half: the retina, its blood vessels, the blind spot where the optic nerve leaves, and the shiny blue-green tapetum that reflects light.
Relate each structure to a disorder and its technology: a cornea too curved (myopia) corrected by spectacles or reshaped by laser surgery, and a clouded lens (cataract).

What you should see

The dissection reveals the tough white sclera, a thick layered cornea, clear watery aqueous humour, a pigmented iris with its pupil, a lens about the size of a squashed marble that magnifies print, clear jelly-like vitreous humour, and the thin retina attached at the optic nerve, with the shiny blue-green tapetum beneath it, as the source describes. The learner knows it worked when the lens magnifies print and each structure has been matched to its role in focusing or detecting light.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

The lens does all the focusing; the cornea does most of the bending of light.
The pupil is a structure; it is an opening in the iris.
The image forms upright on the retina; it is inverted and the brain interprets it.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Biology Stage 6 Syllabus (2017), current: Year 11 taught to the end of 2026 and Year 12 to Term 3 2027BIO12-15 BIO11/12-7
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

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