The ever moving eye

9th September 2005 at 01:00
Each receptor - rod or cone - on the retina is only briefly stimulated by incoming light. So if the eye was held in a fixed position, an image focused on the retina would fade within seconds. So how can you gaze longingly at a piece of cake without it disappearing? Well, no matter how hard you stare, your eye doesn't stay still. There are constant movements of various kinds - frequent little jerks called "saccades" (from an old French word meaning the snap of a sail in the wind), as the eye scans what you are looking at, constantly bringing different sets of receptors into play. (The minute size and close packing of the receptors means that only small movements are necessary.) Look in a mirror and you'll never see your own saccadic movement - or any other kind of eye movement for that matter - because there's a clever neural trick that shuts down the visual system while the eyes are actually on the move and protects you from the visual shakes. Try shutting one eye and gently pushing the other with your finger if you want to know what life might be like without that protection.

Subscribe to get access to the content on this page.

If you are already a Tes/ Tes Scotland subscriber please log in with your username or email address to get full access to our back issues, CPD library and membership plus page.

Not a subscriber? Find out more about our subscription offers.
Subscribe now
Existing subscriber?
Enter subscription number

Comments

The guide by your side – ensuring you are always up to date with the latest in education.

Get Tes magazine online and delivered to your door. Stay up to date with the latest research, teacher innovation and insight, plus classroom tips and techniques with a Tes magazine subscription.
With a Tes magazine subscription you get exclusive access to our CPD library. Including our New Teachers’ special for NQTS, Ed Tech, How to Get a Job, Trip Planner, Ed Biz Special and all Tes back issues.

Subscribe now