Control of Movements of the Eye ball

4. Optic nerve fibers Control of Movements of the Eye ball

5. Extra ocular muscles • Six muscles • Medial rectus • Lateral rectus • Superior rectus • Inferior rectus • Superior oblique • Inferior oblique

6. Extra ocular muscles • Function in pairs • Lateral and medial recti – side to side movements(adduction & Abduction) • Superior and inferior recti - upward and downward movement • Superior and inferior oblique – rotational movements

7. Innervationof extra ocular muscles abducent nerve (VI) • Lateral rectus –------ • Superior oblique --- • Medial rectus • Superior rectus • Inferior rectus • Inferior oblique • Nuclei are interconnected by Medial longitudinal fasciculus • Also connected to vestibular nuclei • Reciprocal Innervation of the pairs of muscles trochlear nerve (IV) occulomotor nerve (III)

8. Extra ocular muscles of the eye

9. Fixation movements • Voluntary fixation mechanism • Unlocking • Pre-motor cortex in frontal lobe -Area8 • Fronto-tectal tract • Involuntary fixation mechanism • Locking • Secondary visual area in occipital cortex • Occipito-collicular and occipito-tectal

10. Neural pathways for control of conjugate movement of the eyes.

11. Three types of fixation movements • Continuous tremor • Frequency 30-80 • Image tremors on different photoreceptors • Slow drift • To one side or the other • Till the image reaches the margins of the fovea • Sudden flick • Opposite to slow drift • To bring the image back in the fovea

12. Conjugate eye movements Saccadic movements Fast eye movement to place the object on to the fovea or to move the eyes from one object to another (up to 800’/sec) Smooth pursuit slow eye movements to maintain fixation on a target Non – optical reflexes(V-O Reflex) vestibular reflexes which maintain eye position with respect to any changes in head and body position

13. Opticokinetic movement • Saccadic movement • Jumping of eyes from one object, frame, scene etc to next • Driving- saccades from frame to frame • Reading – saccades from word to word • 10% time for unlocking • 90% time to keep the image locked

14. Three types of fixation movements

15. Superior colliculus • Responsible for • Control of conjugate movement of the eyes • Control of movement of head • Control of movement of whole body Through medial longitudinal fasciculus even if visual cortex has been destroyed

16. Autonomic nerves to the eyes

17. Autonomic nerves to eyes • Parasympathetic pre-ganglionic neurons in Edinger-Westphal nucleus • Fiber in occulomotor nerve • Ciliary ganglion contains postganglionic neurons • Short ciliary nerve • Supply • Ciliary muscles - accommodation • Sphincter pupillae muscles – light reflex

18. Autonomic nerves to eyes • Sympathetic pre-ganglionic neurons in intermediolateral horn of 1st spinal segment • Synapse in superior cervical ganglion of sympathetic chain • Post ganglionic fibers pass along carotidartery and its branches • Supply 3 muscles 1. Dilator pupillae muscles (radial muscle of iris) 2. Smooth muscle embedded in upper eye lid 3. Ciliary muscle

19. Autonomicinnervation of the eye

20. Pupillary light reflex • Light shone in eye → constriction of pupil • Reflex arc • Retina (photoreceptors) • Optic nerve • Pretectal nuclei • Edinger-Westphal nuclei • Occulomotor nerve • Ciliary ganglion • Short ciliary nerve • Sphincter pupillae muscles • Consensual light reflex- constriction of the pupil of opposite eye • Optic chiasma crossing • Some fibers from pretectal nuclei cross to opposite side as well

21. Pathway of Pupillary light reflex

22. Abnormal pupillary reflex • Damage in Pretectal region (CNS syphilis, alcoholism, encephalitis ) • Chronically constricted pupil • Light reflex absent • Accommodation reflex may be present Argyll Robertson pupil

23. Horner’s syndrome • Interruption of sympathetic supply from superior cervical ganglion • Constricted pupil • Ptosis – drooping of upper eye lid • Vasodilatation • Absence of sweating