Eye Flickers 'May Stop Blindness' (2009-02-13)
by The Press Association
Unconscious flickering eye movements once thought to be random "motor noise" may in fact be necessary to stop us going blind, a study has shown.
The imperceptible jumps and jiggles known as "microsaccades" mean that a really steady stare is impossible. Even when trying to fix a gaze on a stationary target, the eyes are always moving.
Experts have long dismissed these movements as the accidental result of spurious nerve signals.
But new research shows they are actively controlled by the same brain region used to scan newspaper columns or track a moving object.
Scientists now think microsaccades provide a vital function by "refreshing" images on the retina which would otherwise fade away.
Dr Richard Krauzlis, from the Salk Institute in La Jolla, California, focused on the superior colliculus, the "command centre" in the brain responsible for eye-tracking.
He found that the brain region played an integral part in the neural mechanism that controlled microsaccades.
Individual neurons in the superior colliculus were also highly specific about particular directions and strengths of microsaccade eye movement.
The evidence suggested that microsaccades were necessary for normal vision, said the researchers, whose findings are reported today in the journal Science.
Co-author Dr Ziad Hafed, also from the Salk Institute, said: "Because images on the retina fade from view if they are perfectly stabilised, the active generation of fixational eye movements by the central nervous system allows these movements to constantly shift the scene ever so slightly, thus refreshing the images on our retina and preventing us from going 'blind'."