Download III

Ocular Motor Nerves
Visual Pathways
– Neuroanatomy –
for grade III medical students
蔡子同
成大醫院神經科
2012/05/09
Visual System
-- Afferent and Efferent --
• Afferent Visual System
– Retina (ganglion cell axons), Optic nerve, Optic
chiasm, Optic tract, Lateral geniculate nucleus
(thalamic relay nucleus), Optic radiation, Visual cortex
(occipital lobe)
• Efferent Visual System
– Extraocular muscles
– Cranial nerves
– Supranuclear pathways
• Ocular Autonomic Pathways
– Sympathetic pathway
– Parasympathetic pathway
Cranial Nerves
II Optic nerve
III Oculomotor nerve
IV Trochlear nerve
VI Abducens nerve
Manifestations of the Visual System Dysfunction
• Afferent Visual System
– Visual loss (loss of visual acuity)
– Visual field defect
• Efferent Visual System
– Diplopia (double vision)
– Gaze palsy
– Ptosis (blepharoptosis)
• Ocular Autonomic Pathways
– Anisocoria (unequal pupil size)
– Mild ptosis
Visual System
-- Afferent and Efferent --
• Afferent Visual System
– Retina (ganglion cell axons), Optic nerve, Optic
chiasm, Optic tract, Lateral geniculate nucleus
(thalamic relay nucleus), Optic radiation, Visual cortex
(occipital lobe)
• Efferent Visual System
– Extraocular muscles
– Cranial nerves
– Supranuclear pathways
• Ocular Autonomic Pathways
– Sympathetic pathway
– Parasympathetic pathway
Eye Ball; Retina; Fundus
Retina
Cellular Organization of the Retina
Cell Layer
Neuronal and Glial Nuclei
Outer nuclear layer
• Photoreceptors (rod; cone)
Inner nuclear layer
• Horizontal cells
• Bipolar cells
• Interplexiform cells
• Amacrine cells
• Müller cells
Ganglion cell layer
• Ganglion cells
• Displaced amacrine cells
• Astrocytes
Miller NR et al (eds): Walsh & Hoyt's Clinical Neuro-Ophthalmology: The Essentials, 2nd ed, 2008. Chapter 2, pp 43
Visual Pathway
Visual Field
Confrontation test
*** Visual Pathways
Visual Pathways
*** Visual Field Defects
Localization
Visual System
-- Afferent and Efferent --
• Afferent Visual System
– Retina, Optic nerve, Optic chiasm, Optic tract,
Optic radiation, Cortex
• Efferent Visual System
– Extraocular muscles
– Cranial nerves
– Supranuclear pathways
• Ocular Autonomic Pathways
– Sympathetic pathway
– Parasympathetic pathway
*** Extrinsic Ocular Muscles
Superior view
Anterior view
Right lateral view
Actions of the Extraocular Muscles
-- with the Eye in Central Position -Cranial
nerve
Primary
action
Secondary
action
Tertiary
action
Medial rectus
III
Adduction
--
--
Superior rectus
III
Elevation
Intortion
Adduction
Inferior rectus
III
Depression
Extortion
Adduction
Inferior oblique
III
Extorsion
Elevation
Abduction
Superior oblique
IV
Intorsion
Depression
Abduction
Lateral rectus
VI
Abduction
--
--
Muscle
Origins of the Ocular Motor Nerves
- Sagittal & transverse sections of the Brainstem -
Ocular Motor Nerves
Schuenke M et al. Thieme Atlas of Anatomy- Head and Neuroanatomy, Thieme, 2007
Oculomotor Control
- Final Common Pathway -
Conjugate Eye Movement-- Gaze
Purposes of Eye Movements
• Purpose of eye movements
– to place and maintain the image of regard
on the foveas
• Classification of eye movements
– saccade
– smooth pursuit
– vestibuloocular reflex
– optokinetic response
– vergence
Pathways between Semicircular Canals and
Eye Muscles in the Cat
Stimulation
Inhibition
Pathways of Saccade- Horizontal Gaze
Ocular Motor Control System
INC
III
MLF
PPRF
Vestibular
nucleus
Visual System
-- Afferent and Efferent --
• Afferent Visual System
– Retina, Optic nerve, Optic chiasm, Optic tract,
Optic radiation, Cortex
• Efferent Visual System
– Extraocular muscles
– Cranial nerves
– Supranuclear pathways
• Ocular Autonomic Pathways
– Sympathetic pathway
– Parasympathetic pathway
*** Pupillary Light Reflex
-- Sympathetic & parasympathetic pathways --
Parasympathetic
Sympathetic
*** Intrinsic Ocular Muscles
• Ciliary muscles (parasympathetic)
– When the ciliary muscle contracts, it pulls
the choroid forward and relaxes the
zonular fibers. As these fibers become lax,
the intrinsic resilience of the lens causes it
to assume the more convex relaxed
shape.
• Pupillary sphinctor (parasympathetic)
– an anular muscle
– contraction of the muscle constricts the
pupil
• Pupillary dilator (sympathetic)
– radially disposed
– contraction of the muscle dilates the pupil
Schuenke M et al. Thieme Atlas of Anatomy- Head and Neuroanatomy,
Thieme, 2007
Pupillary Abnormality
Pupillary Light Reflex and Accommodation Reaction
•
Light reflex– The afferent pathway is the optic nerve
and tract, from the retina to the pretectal region of the
midbrain. The efferent pathway is in the oculomotor
nerve: parasympathetic fibers from the accessory
oculomotor nucleus (E-W nucleus), synapsing in the
ciliary ganglion, and supplying the sphincter pupillae.
Because of contralateral connections, exposure of only
one eye to light causes constriction of both pupils
(consensual light reflex).
•
Accommodation reaction– The afferent pathway
extends from the retina to the visual cortex, and then to
the pretectal region. The efferent pathway, similar to that
of the light reflex, ends in the ciliary muscle
(accommodation for focusing on near objects), sphincter
pupillae (miosis), and medial rectus (convergence of the
eyes).
Levator Palpebrae Superioris;
Superior Tarsal Muscle (or Müller’s Muscle)
Schuenke M et al. Thieme Atlas of Anatomy- Head and Neuroanatomy, Thieme, 2007