Safety  You’ll be using a scalpel to cut the eye, which can just as easily cut you!  Handling raw meat can be dangerous – wear gloves, and wash hands thoroughly afterwards

Eyes  The eyes have come from the butcher shop – the animals have not been especially killed for this dissection  If you wish to try this at home, most butchers can accommodate getting eyes.  Try to get eyes with the muscles and fat still attached, and if possible pick the eyes the day of the dissection – they are easier to cut when fresh  Remember to think about all safety aspects…

The Eye

Examination  Firstly examine the outside of the eye  Notice the sclera, the tough outer covering of the eyeball; the fat and muscles surrounding the eye; the cornea (covering at the front of the eye) – this would have been clear when the animal was alive; the pupil (the dark oval in the middle); and the iris (the coloured part of the eye)

Fat & Muscle  Cut away the fat and muscle

Incision  Use the scalpel to make an incision in the cornea (be careful)!  Cut until the clear liquid is released ( aqueous humour ) which keeps the shape of the cornea

Sclera  Make an incision through the sclera in the middle of the eye

Cornea  Using scissors cut around the middle of the eye, cutting it in half – on the front will be the cornea  The cornea is pretty tough – it helps protect your eye, as well as helping in seeing by bending the light that enters the eye  Now cut the cornea (listen for the crunch)

Iris  Pull out the iris (lies between the cornea and lens ) – it may be stuck or may have stayed with the back of the eye  Notice the hole in the centre of the iris – that is the pupil which lets light into your eye (the iris contracts or expands, changing the shape of the pupil depending on the light conditions)

Viterous Humour  The back of the eye is filled with a clear jelly – the viterous humour (helps maintain shape)  Remove the lens (a clear lump)

Lens  The lens feels soft on the outside, and hard in the middle – hold the lens up and look through it…  Be careful, they are quite delicate!

Retina  Empty out the viterous humour and you should notice some blood vessels that are part of a thin fleshy film – this is the retina  Before the dissection the viterous humour pushed against the retina so it lay flat on the back of the eye (in may now be in a wad)  The retina contains cells which detect light, which then send the messages to the brain

Optic Nerve  The retina is attached to the back of the eye at one spot – this is where all the nerves from the cells meet, going out the back of the eye (the optic nerve )  The spot where the retina is attached is the blind spot (no light sensitive cells are here, so any light which lands here cannot be seen)!

Tapetum  Under the retina the back of the eye is covered with shiny blue- green material (the tapetum ) which reflects light from the back of the eye (shine a light at a cat during the night and the cat’s eyes seem to glow - this is the tapetum reflecting the light)

Optic Nerve  Look at the other side of the back of the eye – locate the optic nerve  Pinch the optic nerve with scissors to separate the fibers (squeezing the nerve may cause myelin (fatty layer) to come out)

Clean Up  Place all material in the plastic bag, as well as gloves and tissues  Wash the desk thoroughly, followed by your hands (make sure you use the disinfectant)

Online  Follow this link for an online dissection… Eye Dissection