1. Eye movements
Domina Petric, MD

2. Eye movements adjust fixation when visual target moves
adjust fixation during head movements
adjust fixation when acquiring a new target

3. Eye muscles Abducens nucleus, abducens nerve
Ipsilateral rectus lateralis muscle
ABduction
Trochlearis nucleus, trochlearis nerve
CONTRALATERAL superior oblique muscle
Downward gaze, intorsion
Occulomotor nucleus, occulomotor nerve
Ipsilateral inferior, superior and medial rectus muscle; inferior oblique muscle
Upward gaze, ADuction, downward gaze without intorsion

4. Eye movements
Conjugate eye movements: eyes move in the same direction
Disconjugate eye movements: eyes move in opposite direction
Saccades: quick, ballistic
Smooth pursuit: slow, visually guided
Optokinetic: smooth pursuit and saccades combination, visually guided
Vestibulo-ocular: slow, vestibular guided
Vergence (convergence, divergence): visually guided near and far fixations

5. Saccades
Saccade is a quick, ballistic eye movement that allows us to change fixation point from one target to another.
200 ms is necessary interval between the onset of the target and the onset of the eye movement for target fixation.

6. Smooth pursuit eye movements
Visually guided eye movements.
After catch-up saccade, eyes can track the target smoothly.

7. Optokinetic nystagmus
Optokinetic nystagmus has two components: saccade component and smooth pursuit component.
Saccade
Saccade
Smooth pursuit
Smooth pursuit

8. Both eyes are in adduction.
Convergence
Both eyes are in adduction.
Near objects fixation.

9. Both eyes are in abduction.
Divergence
Both eyes are in abduction.
Far objects fixation.

10. PPRF
PPRF is Paramedian Pontine Reticular Formation and it is horizontal gaze center.
PPRF controls horizontal movements of the eyes.
When we look at the right, right PPRF sends excitatory signals to the right abducens nucleus so the right lateral rectus muscle is activated.
Internuclear neuron that crosses the midline, sends excitatory impulse to the contralateral (in this case left) oculomotor nucleus: activation of the left medial rectus muscle.

11. Vertical gaze center is located in the mesencephalon.

12. Upper motor neuronal control of eye movements
Frontal eye field
Superior colliculus in the midbrain

13. Upper motor neuronal control of eye movements
Sensory map represents locations in the contralateral visual hemifield.
Sensory map is present in both frontal eye field and superior colliculus.
There is also a motor map for saccadic eye movements located in frontal eye field and superior colliculus.

14. Frontal eye field (Brodmann´s area 8)
Frontal eye field is connected with ipsilateral superior colliculus and with contralateral gaze centers of the reticular formation (horizontal and vertical gaze centers).
Lesion in the frontal eye field or in the superior colliculus causes deficit in saccadic eye movements.
Frontal eye fields are concerned with intentional saccades to the opposite (contralateral) direction.
If the patient has a stroke involving the anterior parts of the premotor cortex, that patient can not intentionally look at the opposite side: if the left frontal eye field is damaged, patient can not look to the right side if asked.

15. Superior colliculus
Superior colliculus generate express saccades that are not associated with planned movements of the eyes.
If we hear a noise, we will automatically look towards the source of that noise.

16. Literature
Leonard E. White, PhD, Duke University