Physiology - Eye movement

Eye movement

Rapid eye movement

• Eyes move with rapid jerks (saccadic movements) when looking around
• Generates a continuous series of images of different areas
• Eyes fixed on individual areas for 0.2-0.6 seconds before next rapid eye movement
• Surrounding is perceived to be stable when the brain interprets this continuous series of images
• Points of fixation are not evenly distributed but are concentrated around contours and distinctive features

Slow eye movement

• Allow focus on moving object when head is stationary or focus on stationary objects when animal is moving
• Vestibulo-ocular reflex
• Fix image on retina when head is moving
• Ocular muscles move eyeballs simultaneously but in opposite direction  to head movements
• Optokinetic reflex
• Stabilise moving image on retina when head is stationary
• Rapid saccade brings eye back to middle position just before slow eye movement reaches outer limit

References

1. Sjaastad O.V., Sand O. and Hove K. (2010) Physiology of domestic animals, 2nd edn., Oslo: Scandinavian Veterinary Press.