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Blind spot test

Introduction
Public summary: 

Did you know that everyone has a blind spot in their eyes? Never noticed before? Use our blind spot test to find yours!

A simple test to show that there is a blind spot on the retina of the eye
Useful information
Kit List: 

Blind spot test (laminated sheets)

Frequency of use: 
1
Explanation
Explanation: 

GENERAL:

Use with eye model and optical illusions.

TO DO:

•Let the kids find their blind spots using the first diagram
•Close/cover the left eye – get child to stare at cross mark in diagram with right eye
•Off to the right they should be able to see the spot – check they can (but they shouldn’t look at it directly!)
•Get the child to move slowly towards the diagram/bring the diagram closer towards their eye while still looking at the cross mark
•At a particular distance the spot will disappear (it will reappear again if you move closer)
•Kids often get quite excited and move the paper quite fast which means they miss the point when they can see their blind spots – important to make them slow down!
•Second and third diagrams are to reinforce the principle that the brain “fills in” what it can’t see – should see a yellow background in the second picture, and in the third picture, the line should complete

EXPLANATION:

•Start by talking about the basic structure of the eye (using an eye model – kids will often already know quite a bit)
•Inside our eye there is a “black screen” called the retina (you can see this when you look through your pupil – that’s why the pupil is black)
•Retina is a bit like a TV screen/camera – there are lots of detectors that “see” light
•Brain changes this light into a picture
•How does the light get from the screen in the eye to the brain? Travels down a “path” called the optic nerve
•At the point where the optic nerve leaves the eye – no light can be detected on the retina (no photoreceptors to respond to light) – brain gets no information from the eye about this particular part of the picture of the world
•Because of this – have a blind spot! But why do we not notice them normally?
•Most people assume that what you see is pretty much what your eye sees and reports to your brain – brain actually adds very substantially to the report it gets from your eye, so a lot of what you see is actually “made up” by the brain – brain fills in the picture according to what it “thinks” it should look like

OTHER THINGS TO TALK ABOUT:

Do all species have a blind spot?:
No. Interestingly an octopus does not have a blind spot! The retina of the octopus is constructed more logically than the mammalian retina. The photoreceptors in the octopus retina are located in the inner portion of the eye and the cells that carry information to the brain are located in the outer portion of the retina. Therefore, the octopus optic nerve does not interrupt any space of retina.

Risk Assessment
Date risk assesment last checked: 
Sat, 27/01/2018
Risk assesment checked by: 
Matt Worssam
Date risk assesment double checked: 
Wed, 07/02/2018
Risk assesment double-checked by: 
Esmae
Risk Assessment: 
DESCRIPTION Various displays - can be attached to display boards (but mostly just used flat on a table)
Closing eye.
RISKS It it possible that the display boards could fall on someone. If used properly this should be unlikely
Reduced vision may increase risk of tripping.
ACTION TO BE TAKEN TO MINIMISE RISKS

Use light professional displayboards so they are not too heavy

Make sure the display boards are stable. Do not use them flat without taping them to something solid.

Mark boards with highly visible stuff (eg. hazard tape, white paper) if they are being used in the dark room.
Get people to remain still.

ACTION TO BE TAKEN IN THE EVENT OF AN ACCIDENT Call first aider in event of injury.
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