Neural Mechanisms Engaged in Control of Eye Movements The
purpose of eye movements is to ensure clear, optimal vision. In
order to see clearly, images must be held steady on the retina.
Best visual acuity is achieved when the image of the object of
interest is brought to and held on the fovea of the retina. Two
main types of eye movements are responsible for that: those that
keep images stable on the retina (gaze holding mechanisms) and
those that change the line of sight (gaze shifting mechanisms).
Several functional classes of eye movements have been defined;
each has distinctive physiological properties that suit best to
its particular task. Thus, vestibular and optokinetic eye
movements hold images of the seen world steady on the retina
during perturbations of the head. Saccades are rapid eye
movements that bring the image of an object of interest,
detected in the periphery of vision, onto the fovea where it can
be seen best. Smooth pursuit eye movements place the images of a
moving target close to fovea.