Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD

Retina - contains• Pigment epithelial cells- absorb light

that passes through the retina• First neuron

• Rods- vision in light of low intensity

• Cones- visual acuity and color vision

• Second neuron• Bipolar- second neurons of visual

pathway• Ganglion

• Ganglion- third neurons of visual pathway

Visual Pathways

Eye• Lens• Cornea• Iris• Suspensory ligaments• Ciliary body• Ciliary muscle• Retina• Choroid• Sclera• Subarachnoid space• Central retinal artery and vein• Optic nerve• Vitreous body• Conjunctiva

Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD

Visual Pathway-• Light travels through retina from

internal to external exciting the rods and cones

• Impulse is transferred from rods and cones to bipolar cells

• Bipolar cells synapse on the dendrites of the ganglion cells

Additional areas:• Optic disc- Area optic nerve exits retina

(blind spot- no receptors)• Macula lutea- central region of the

retina• Fovea centralis- area of the central part

of the retina that is indented and contains mainly cones for visual acuity

Visual Pathway- forth order neurons• Cell body located in the lateral

geniculate body• Axon travels posteriorly (optic

radiations)• Terminates in the visual cortex in the

occipital lobe

Visual Pathway-• Ganglion cells form the optic nerve at

the level of the optic disc• Optic nerves combine to form optic

chiasm• Enters lateral geniculate body to

synapse

Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD

1. 1. Right eye blindness - trauma, optic neuritis

2. 2. Bitemporal hemianopsia - pituitary tumors

3. 3. Right nasal hemianopsia - pressure by aneurysm of internal carotid artery

4. 4. Left homonymous hemianopsia - abscess or tumor of temporal lobe

5. 5. Left homonymous hemianopsia - anterior choroidal artery dysfunction

6. 6. Left homonymous superior quadratic anopsia - temporal or occipital lobe dysfunction

7. 7. Left homonymous inferior quadratic anopsia - parietal or occipital lobe tumor

8. 8. Left homonymous hemianopsia with macular preservation - posterior cerebral artery dysfunctions, tumors, trauma

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Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD

Visual Reflexes• Light reflex (constriction- parasympathetic): when light enters the pupil the pupil constricts

• Neuronal elements of the retina• Optic nerve• Optic chiasm• Optic tract• Enter the brachium of the superior colliculus (superior brachium)• Pretectal region• Oculomotor nuclear complex (Edinger-Westphal nucleus)• Preganglionic parasympathetic axons to the ciliary ganglion behind eye• Short ciliary nerves• Terminate on the constrictor muscle of the iris

Lecture 14 - Visual

Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD

Visual Reflexes• Light reflex (dilation- sympathetic): when the pupil widens. Occurs passively when parasympathetic

tone decreases and actively when sympathetic tone increases• Hypothalamus• Spinal cord (T1)• Ventral root• White communicating rami• Ascend sympathetic trunk• Synapse in superior cervical ganglion with post-synaptic sympathetic ganglion• Travel in the carotid plexus• Terminate on the dilator muscle of the iris

Lecture 14 - Visual

Neuroanatomy OC TH 5090/PH TH 7050 - K. Bo Foreman PT, PhD

Visual Reflexes• Accommodation reflex: Process in which a clear visual image is maintained as gaze is shifted from a

distant to a near point• 3 components

• Convergence of the eyes• Pupillary constriction• Thickening of the lens

• Initiated by occipital cortex• Impulses go to:

• Edinger-Westphal nucleus for changes in the lens and pupil (parasympathetic)• Somatic nuclei: for convergence of the eyes (medial rectus