6.7 visual pathway
DESCRIPTION
visual pathwayTRANSCRIPT
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Visual Pathways
Oliver Glenn C. Domingo, MD, PTRP, FPSOHNSDepartment of Anatomy, College of Medicine
UERMMMCI
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REFERENCES• Snell, R.S. Clinical Neuroanatomy, 6th ed.,
Lippincott Williams & Wilkins, 2006.• Carague-Lansang, E.N., et al. Lansang Notes:
Modules in Neuroanatomy, 4th ed., UERMMMC: Quezon City, 2006.
• Moore, K.L. and Dalley, A. F. Clinically Oriented Anatomy, 5th ed., Lippincott Williams & Wilkins, 2006.
• Gilman, S. and Newman, S.W. Manter and Gatz’s Essentials of Clinical Neuroanatomy and Neurophysiology, 10th ed., F.A. Davis Co., 2003.
• Netter, F.H. Atlas of Human Anatomy, 4th ed., Elsevier Saunders, 2006.
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Objectives
Demonstrate knowledge & understanding of the optic and visual pathway.
Demonstrate knowledge & understanding of the pupillary apparatus.
Demonstrate knowledge & understanding of the neuroanatomical basis of ocular movements.
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Objectives
Describe the supranuclear mechanisms for ocular movement.
Trace the pathways involving the saccadic, smooth pursuit and vergence systems.
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VISUAL SYSTEM
• Eye & Retina
• Optic nerves
• visual
pathways
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OPTICAL COMPONENTS
• Cornea
• Pupillary opening of the iris
• Lens
• Retina
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• Cornea• Aqueous humor
• lens• vitreous humor
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• FOVEA CENTRALIS
• - a small depression at the center of the macula lutea
• - cones
• PERIPHERAL RETINA
• - rods > cones
• PHYSIOLOGIC BLIND SPOT
• - corresponds to the optic disc which has no rods and cone
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RETINA
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RETINAL STRUCTURE
• Outer layer: rods and cones
• Middle layer: bipolar neurons: horizontal and amacrine.
• Inner layer:
• ganglion cells.
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VISUAL PATHWAYS
MIDBRAIN
Bipolar neurons
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VISUAL PATHWAY
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VISUAL PATHWAY
• VISUAL FIELD
RETINAL FIELD
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Anatomy of visual pathwayRight eye Left eye
Temporal TemporalNasalNasal
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RETINOGENICULOSTRIATEPATHWAY
Optic nerve
Nasal retina
Optic chiasm
Optic tract
Optic radiation
Temporal retina Temporal retina
Lateral Geniculate Body
LEFT
RIGHT HEMISPHERE
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Optic nerve
Nasal retina
Optic chiasm
Optic tract
Optic radiation
Temporal retina Temporal retina
Lateral Geniculate Body
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LATERAL GENICULATE NUCLEUS
• Nucleus in the thalamus
• 1° visual cortex
• laminated
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LATERAL GENICULATE NUCLEUS
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RETINOTROPIC ORGANIZATIONS
Projection on rightdorsal lateralgeniculate nucleus
Projection on leftdorsal lateralgeniculate nucleus
Projection onleft retina
Projection onright retina
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OPTIC RADIATIONS
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Optic Radiations and Projections to the Primary
Visual Cortex• Geniculocalcarine fibers
• Meyer’s loop–upper part of the
contralat visual field
• 1° cortex –Broadman’s Area 17
• Lines of Gennari–Layer 4
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Stripe of Gennari in area 17
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RETINOTOPIC REPRESENTATION OF THE VISUAL FIELDS
Calcarinesulcus
Calcarinesulcus
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VISUAL FIELD DEFECTS(Lesions of optic pathway)
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• What will happen if the left optic nerve is severed?
• What will happen if a person has a tumor in the pituitary gland (just below the optic chiasm) and the inner fibers are destroyed?
• What will happen if a person suffers a brain tumor on the right side of the brain around the lateral geniculate body?
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CONFRONTATION TEST
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VISUAL PATHWAYS
MIDBRAIN
Bipolar neurons
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Connections of visual pathway with midbrain
• Pretectal nuclei–pupillary light reflex
• Superior Colliculus & Medial longitudinal fasciculus–lens accomodation, eye movements–other visual reflexes
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ACCOMODATION REFLEX
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ARGYLL ROBERTSON PUPIL
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PUPILARY DILATATION
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NeuroAnatomical Basis of Extraocular Movement
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vertical axis
Horizontal axis
AP axis
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YOKE MUSCLE COMBINATION
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CONJUGATE EYE MOVEMENTS & THEIR
CONTROL• Conjugate Gaze–lateral–vertical gaze upward–vertical gaze downwad
• Vergence
• saccades
• smooth pursuit
• Vestibulo-ocular Reflex
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CRANIAL NERVES CONCERNED WITH EYE MOVEMENT
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SUPERIOR COLLICULUS
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NEURAL BASES OF EXTRAOCULAR MOVEMENT
• Supranuclear level (cerebral hemispheres & brainstem)–Frontal gaze center (area 8):voluntary rapid eye
movement–Occipital gaze center (areas 18 & 19): smooth
pursuit movement–PPRF: center for lateral gaze–RiMLF(pretectal region near superior colliculus):
center for vertical eye movements
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NEURAL BASES OF EXTRAOCULAR MOVEMENT
• Nuclear level–Nucleus of CN II and IV in the midbrain & CN VI in
the pons
• Infranuclear level–CN III, IV, VI
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TYPES OF EYE MOVEMENT(PATHWAYS)
• Fast saccadic eye movement• Slow (SMOOTH) pursuit• Vergence eye movements• Vestibuloocular reflex (VOR) eye movements
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SACCADIC SYSTEM
• Horizontal voluntary rapid eye movement–Broadman Area 8–contralateral PPRF–ipsilateral abducens nucleus
• ipsilat lateral Rectus
– via MLF– contralat occulomotor
nucleus–contralat medial rectus
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SACCADIC SYSTEM
• Vertical voluntary rapid eye movement–Broadman Area 8–pretectal (RiMLF)–occulomotor nucleus
• SR, IR, IO
–trochlear nuclei• SO
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SMOOTH PURSUIT
Broadman Area 18, 19
Retifular Formation
PPRF/RiMLF
ipsilat abducens nucleus
contralat oculomotor nucleus
Lateral RectusMedial Rectus
internal capsule
pons
trochear nuclei
oculomotor nuclei
Superior Oblique SR, IR, IO
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SACCADIC AND SMOOTH PURSUIT SYSTEM
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VESTIBULO-OCULAR REFLEX
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DOLL’S EYE REFLEX
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MEDIAL LONGITUDINAL FASCICULUS
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Demonstrate knowledge & understanding of the optic and visual pathway.
Name the refractive media of the eye.
Trace the visual pathway (pathway of light to retinal photoreceptors to the primary visual cortex).
Describe the course and origin of optic nerve, chiasm and tract.
Illustrate the retinotopic organizations as it relates to the LGB and primary visual cortex
Illustrate the different visual field defects arising from lesions along the visual pathway.
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Demonstrate knowledge & understanding of the pupillary apparatus.
Locate the Edinger-Westphal nucleus, pretectal nucleus and superior colliculus.
Trace the pathway for direct & consensual light reflex.
Trace the pathway for accomodation reflex.
enumerate the changes in the eye that occur during accomodation.
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Demonstrate knowledge & understanding of the neuroanatomical basis of ocular
movements.
Describe the action of the extraocualr muscles in relation to conjugate gaze.
Describe the supranuclear mechanisms for ocular movement.
Trace the pathways involving the saccadic, smooth pursuit and vergence systems.
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• Thank YouThank You