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Published byVerawati Setiawan Modified over 6 years ago
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2/19/20192/19/20192/19/20192/19/20192/19/20192/19/20192/19/20192/19/20192/19/2019
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2/19/20192/19/20192/19/20192/19/20192/19/20192/19/20192/19/20192/19/20192/19/2019
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Control of Movements of the Eye ball
Optic nerve fibers
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Extra ocular muscles Six muscles Medial rectus Lateral rectus
Superior rectus Inferior rectus Superior oblique Inferior oblique
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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
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Innervation of extra ocular muscles
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 abducent nerve (VI) trochlear nerve (IV) occulomotor nerve (III)
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Extra ocular muscles of the eye
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Fixation movements Voluntary fixation mechanism
Unlocking Pre-motor cortex in frontal lobe -Area 8 Fronto-tectal tract Involuntary fixation mechanism Locking Secondary visual area in occipital cortex Occipito-collicular and occipito-tectal
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Neural pathways for control of conjugate movement of the eyes.
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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
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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
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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
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Three types of fixation movements
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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
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Autonomic nerves to the eyes
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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
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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 carotid artery 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
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Autonomic innervation of the eye
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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
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Pathway of Pupillary light reflex
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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
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Horner’s syndrome Interruption of sympathetic supply from superior cervical ganglion Constricted pupil Ptosis – drooping of upper eye lid Vasodilatation Absence of sweating
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