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![Learning Objectives
Relationship of bipolar & ganglion cells to the visual pathway
Relationship of retinal quadrants to visual field quadrants
Understanding of monocular vs. binocular visual fields
Importance of “corresponding points” on the retinae & the “Blind spot”
Components of the visual pathway; nuclei involved; location of
decussations, etc.
Representation of the visual field within the structures of the visual
pathway. [Upper vs. lower fields; Nasal vs.Temporal fields; Macular vs.
Peripheral fields representation]
Visual field deficits associated with damage along the visual pathway
Components & basis of the:
Direct & consensual pupillary light reflex
Pupillary dilation
Accommodation or near reflex
Definition or description of terms: amblyopia, Argyll Robertson pupil,
diplopia, hemianopsia, heteronymous, homonymous, Horner’s syndrome,
Meyer’s loop, quadrantanopsia, retinotopic, scotoma, strabismus
Pg. 1](https://image.slidesharecdn.com/visualpath-220804090614-996de99a/75/VisualPath-ppt-4-2048.jpg)
VisualPath.ppt
- 1. Visual Pathway Med 6573:Nervous System University of Minnesota Medical School Duluth Donna J. Forbes, Ph.D. 29 February 2008
- 2. 2 • Nolte Chapter17 • Netter: Plates 86 and 114 • Related materials from other faculty • Dr. Downing: Histology of the Eye • Dr. Stauffer: Physiology of the Eye • Dr. Trachte: Pharmacology of the Eye • Dr. Hollenhorst: Clinical Ophthalmology • Dr. Meyerson: Neurological Exam • Washington University: The Basic Visual Pathway http://thalamus.wustl.edu/course/basvis.html Pg. 1 References
- 3. 3 • Visual Acuity:Eye, CN II & beyond in the visual pathway • Visual Fields: Central & Peripheral Vision (retina to cortex) • Ocular Motility: (CN III, IV, VI) • Reflexes • Pupillary Light Reflex (CN II & III) • Accommodation (Near) Reflex • Corneal Reflex (CN V & VII) • Retina including Optic disc: (Increased intracranial pressure; status of blood vessels reflecting hypertension, diabetes, etc.) • Visual Pathway: Since it is precisely organized & extends from the rostral to caudal aspect of the hemispheres, lesions along the pathway produce specific deficits that can aid in localizing the lesion. Pg. 1 Eyes are the window to the brain! Eye Exam
- 4. Learning Objectives Relationshipof bipolar & ganglion cells to the visual pathway Relationship of retinal quadrants to visual field quadrants Understanding of monocular vs. binocular visual fields Importance of “corresponding points” on the retinae & the “Blind spot” Components of the visual pathway; nuclei involved; location of decussations, etc. Representation of the visual field within the structures of the visual pathway. [Upper vs. lower fields; Nasal vs.Temporal fields; Macular vs. Peripheral fields representation] Visual field deficits associated with damage along the visual pathway Components & basis of the: Direct & consensual pupillary light reflex Pupillary dilation Accommodation or near reflex Definition or description of terms: amblyopia, Argyll Robertson pupil, diplopia, hemianopsia, heteronymous, homonymous, Horner’s syndrome, Meyer’s loop, quadrantanopsia, retinotopic, scotoma, strabismus Pg. 1
- 5. 5 Pathway extends fromthe ‘front’ to the ‘back’ of the brain. • Precise retinotopic organization • Deficits due to lesions of the pathway give valuable localizing information. The Visual Pathway Pg. 2 OT ON OC VISUAL CORTEX RETINA VISUAL FIELD LGN OPTIC RADIATIONS ON = Optic Nerve OC = Optic Chiasm OT = Optic Tract LGN = Lateral Geniculate Nucleus of Thalamus
- 6. 6 Beginning of thePathway Pg. 2
- 7. 7 Cells of the Retina Pg. 2 Rodsand Cones (Receptors) Ganglion cells axons form the optic nerve Bipolar cells
- 8. 8 Object to beseen Peripheral Retina The next slide looks at the retina as if you are looking through the patient’s pupil via your ophthalmoscope. Central Retina (fovea in the macula lutea) Pg. 2
- 9. 9 Retinal Quadrants nose UTQ UTQ LTQLTQ LNQ LNQ UNQ UNQ Right retina Left retina Papilla (optic nerve head) Macula with fovea centralis Retina as you would see it through the ophthalmoscope & the patient’s pupil Temporal Hemiretina UTQ = upper temporal quadrant LTQ = lower temporal quadrant Nasal Hemiretina UNQ = upper nasal quadrant LNQ = lower nasal quadrant Horizontal Meridian Vertical Meridian Pg. 2 The blind spot in the Visual Field corresponds to the location of the optic nerve head on the NASAL side of the retina.
- 10. 10 Visual Fields &the Visual Pathway Pg. 2 OT ON OC VISUAL CORTEX RETINA VISUAL FIELD LGN OPTIC RADIATIONS ON = Optic Nerve OC = Optic Chiasm OT = Optic Tract LGN = Lateral Geniculate Nucleus of Thalamus The following slides begin with the visual fields and then follow the pathway from the retina to the visual cortex.
- 11. 11 Definition: The entirearea that can be “seen” by the patient without movement of the head and with the eyes fixed on a single spot. Visual Fields Pg. 3 Mapping of Visual Fields: • Confrontational method (see Dr. Meyerson’s “Neurological Exam” notes) • Perimetry (Manual or Automated) Temporal Field of Left Eye Nasal Field of Left Eye F Normal Monocular Visual Field of Right Eye Normal Monocular Visual Field of Left Eye F Monocular Visual Fields Monocular Visual Fields: • Each eye is tested separately. • The monocular visual field is plotted with the Fovea (F) at the center. • The monocular visual field (colored area -- blue for left; green for right in this example) is not round. • Horizontal and Vertical Meridians correspond to those of the retina and divide the visual field into upper temporal, upper nasal, lower temporal and lower nasal quadrants. • Imagine that this is your visual field, i.e. all that you can see with your left eye and your right eye (tested separately) when you look straight ahead and do not move your head or eyes. Vertical Meridian Horizontal Meridian Upper Field of Left Eye Lower Field of Left Eye UTQ LTQ UNQ LNQ
- 12. 12 Blind Spot • 15°to the temporal side of the visual field of each eye • On the horizontal meridian • Corresponds to the location of the optic nerve head 15° to the nasal side of the retina of each eye. Visual Fields Demonstration of the Blind Spot: • Draw the star and box on a piece of paper. • Close your left eye; Look at the star with your right eye; Move paper back and forth until the green box disappears. • Open your left eye and the box can be seen because even though it was falling on the blind spot of the right eye, it is not falling on the blind spot of your left eye. • With both eyes open & binocular vision intact, you don’t realize that there is a blind spot since the corresponding spot on the contralateral retina will see the object. Pg. 3 Temporal Field of Left Eye Nasal Field of Left Eye Normal Monocular Visual Field of Left Eye F F Normal Monocular Visual Field of Right Eye Upper Field of Left Eye Lower Field of Left Eye
- 13. 13 Visual Fields: Binocular Pg. 3 NormalBinocular Visual Field F Right Visual Field Left Visual Field Upper Fields Lower Fields Temporal Field of Left Eye Nasal Field of Left Eye Normal Monocular Visual Field of Left Eye F F Normal Monocular Visual Field of Right Eye Understand the difference between the “monocular visual field of the left eye” vs. the “binocular left visual field” and vice versa for the right counterparts. • Binocular field combines the two monocular visual fields with the foveas (F) aligned with one another. (i.e. the ‘pink area’ in the image to the right) • Left Visual Field seen by both the left & right eyes. • Right Visual Field seen by both the left & right eyes. • Monocular crescent for each eye (blue for left eye & green for right eye) is only seen by the nasal retina of the same eye. Monocular Crescent of Right Eye Monocular Crescent of Left Eye
- 14. 14 Visual Fields: Binocular Binocular visionis dependent upon the extraocular muscles aligning the eyes so that an image falls on “corresponding points” on the retina of each eye. This is essential for the brain to perceive a single image. Diplopia occurs when the images are not aligned to fall on corresponding points of each retina. Pg. 3 Normal Binocular Visual Field F Right Visual Field Left Visual Field Upper Fields Lower Fields Temporal Field of Left Eye Nasal Field of Left Eye Normal Monocular Visual Field of Left Eye F F Normal Monocular Visual Field of Right Eye Demonstration of the Binocular Visual Field & Monocular Crescent: • Look straight ahead • Close your right eye • Move your finger to the right until it disappears • Open right eye to see the pencil -- in the right temporal monocular crescent of your visual field.
- 15. 15 Visual Fields Pg.4 The image of an object in the visual field is inverted and reversed right to left on the retina. • Temporal field of left eye (red & purple) is seen by the nasal retina of the left eye • Nasal field of the left eye (green & yellow) is seen by the temporal retina of the left eye. • Superior field of the left eye (red & green) is seen by the inferior retina of the left eye. • Inferior field of the left eye (purple & yellow) is seen by the superior retina of the left eye. • Similarly, the image is inverted & reversed for the right eye. Retina of Left Eye Retina of Right Eye NOTE: DOTTED OUTLINE = MONOCULAR FIELD OF LEFT EYE SOLID OUTLINE = MONOCULAR FIELD OF RIGHT EYE Binocular Visual Field Monocular Crescent of Right Eye Monocular Crescent of Left Eye Note: To avoid confusion and abide by convention, central representation, visual deficits, etc. will be described in terms of visual fields and not retinal quadrants.
- 16. 16 Visual Pathway • OpticNerve (ON) • = Axons of ganglion cells in the retina of the corresponding eye • Outgrowth of diencephalon, so is a CNS tract & not a ‘true’ cranial nerve. • Myelinated by oligodendrocytes. • Optic Chiasm (OC) • Located just anterior to pituitary • Partial crossing of optic nerve axons in the OC is essential to binocular vision • Axons from temporal fields cross • Axons from nasal fields do not cross • “Wilbrand’s knee” may be artifact Note: Reference point = Visual Fields Pgs. 4 - 5 Retinotopic representation • Central (macular) vision • Peripheral vision Left visual field Right visual field Right retina Left retina Left LGN Tempora l Nasal Tempora l Nasal lateral lateral medial medial LVF LVF UVF UVF E.W. Right visual cortex midbrain Right LGN Left visual cortex Left temporal retina Right temporal retina Nasal retina Ciliary ganglion pretectal nuclei cuneus lingual gyrus Calcarin e sulcus III III Upper field Lower field VISUAL FIELDS: Hatched = binocular Stippled = monocular Central area = macula ON OC OT
- 17. 17 • Optic Tract(OT) • Optic nerve fibers from the optic chiasm continue as the optic tract & terminate in the lateral geniculate nucleus of thalamus. • Each tract contains axons that carry input from the contralateral visual field. • Left OT receives from R. visual field • Right OT receives from the L. visual field Pgs. 4 - 5 Note: Reference point = Visual Fields Retinotopic representation • Central (macular) vision • Peripheral vision Left visual field Right visual field Right retina Left retina Left LGN Tempora l Nasal Tempora l Nasal lateral lateral medial medial LVF LVF UVF UVF E.W. Right visual cortex midbrain Right LGN Left visual cortex Left temporal retina Right temporal retina Nasal retina Ciliary ganglion pretectal nuclei cuneus lingual gyrus III III Visual Pathway Post-Chiasmatic portion of the pathway: From optic tract to visual cortex, each side of the brain deals with the contralateral visual field. Upper field Lower field VISUAL FIELDS: Hatched = binocular Stippled = monocular Central area = macula ON OC OT • Lateral Geniculate Nucleus (LGN) • Primary termination of OT fibers • Each LGN receives input from the contralateral visual field. • OT Projections to pretectum for reflexes
- 18. 18 Retinotopic representation • Central(macular) vision • Peripheral vision • Geniculocalcarine Tract (= optic radiations) • Axons of LGN neurons travel to primary visual cortex (Area 17) via the geniculocalcarine tract located in the retrolenticular and sublenticular portions of the internal capsule. • Axons from upper visual fields take a looping course into the temporal lobe on the way to visual cortex. (=Meyer’s loop) • Axons from lower visual fields take a more direct route to visual cortex. • Macular fibers are in an intermediate location in the optic radiation. Pgs. 4 - 5 Note: Reference point = Visual Fields Left visual field Right visual field Right retina Left retina Left LGN Tempora l Nasal Tempora l Nasal lateral lateral medial medial LVF LVF UVF UVF E.W. Right visual cortex midbrain Right LGN Left visual cortex Left temporal retina Right temporal retina Nasal retina Ciliary ganglion pretectal nuclei cuneus lingual gyrus Calcarin e sulcus III III Meyer’s loop Optic radiation or geniculocalcarine tract Visual Pathway Post-Chiasmatic portion of the pathway: From optic tract to visual cortex, each side of the brain deals with the contralateral visual field. Upper field Lower field VISUAL FIELDS: Hatched = binocular Stippled = monocular Central area = macula ON OC OT
- 19. 19 Visual Pathway Pgs. 4- 5 Note: Reference point = Visual Fields Retinotopic representation • Central (macular) vision • Peripheral vision Left visual field Right visual field Right retina Left retina Left LGN Tempora l Nasal Tempora l Nasal lateral lateral medial medial LVF LVF UVF UVF E.W. Right visual cortex midbrain Right LGN Left visual cortex Left temporal retina Right temporal retina Nasal retina Ciliary ganglion pretectal nuclei cuneus lingual gyrus Calcarin e sulcus III III Meyer’s loop Optic radiation or geniculocalcarine tract Upper field Lower field VISUAL FIELDS: Hatched = binocular Stippled = monocular Central area = macula ON OC OT • Primary Visual Cortex (Area 17) • Located on either side of & within the calcarine fissure. • Upper fields project to the lingual gyrus. • Lower fields project to the cuneus. • Macular representation is most caudal in Area 17. • Peripheral field representation is in the rostral 2/3rds of Area 17. • Lesions of Area 17 result in blindness in the contralateral visual field. • Association Visual Cortex (Areas 18 & 19) • Input from Area 17 & elsewhere • Deals with complex aspects of vision • Lesions of result in visual agnosia.
- 20. 20 Lesions of theVisual Pathway 1. Normal visual fields 2. Blindness of the right eye 3. Blindness of right eye + contralateral left upper quadrantanopia 4. Bitemporal heteronymous hemianopsia 5. Left homonymous hemianopsia 6. Left upper homonymous quadrantanopsia 7. Left homonymous hemianopsia with macular sparing Right Left Definitions Strabismus Diplopia Amblyopia Scotoma Quadrantanopsia - # 3, 6 Hemianopsia - # 4, 5, 7 Heteronymous Defects - # 3, 4 Homonymous Defects - # 5, 6, 7 Congruous Defects - # 5, 6, 7 Incongruous Defects - # 3 Altitudinal Defects - # 6 Masked area = area of visual loss Pg. 6 Aka “field cuts” Fields, not retinal quadrants
- 21. 21 Lesions of theVisual Pathway 1. Normal visual fields 2. Blindness of the right eye 3. Blindness of right eye + contralateral left upper quadrantanopia 4. Bitemporal heteronymous hemianopsia 5. Left homonymous hemianopsia 6. Left upper homonymous quadrantanopsia 7. Left homonymous hemianopsia with macular sparing Right Left Pg. 6
- 22. 22 Right Left Pupillary Constriction (Miosis) Nolte17-38 Afferent limb = Optic Nerve (SSA) Efferent limb = Oculomotor Nerve (GVE) Postganglionic Preganglionic Direct Reflex Consensual Reflex Pg. 7 AKA Pupillary Light Reflex
- 23. 23 Right Left B C Right Left RightLeft Nolte 17-38 Reflex abolished if afferent or efferent is damaged. Pg. 7 Afferent defect Efferent defect
- 24. 24 Pupillary Dilation (Mydriasis) Decreased lightto pupil Severe pain Strong emotional stimulus Reticular Formation Reticulospinal fibers Preganglionic Sympathetic Neurons in Thoracic Cord (T1- T2) (pre-ganglionic sympathetic) Dilation of pupil Superior Cervical Ganglion (post-ganglionic sympathetic) Cortex, Thalamus & Hippocampus ? Hypothalamus (CNS control center for AN S) ? Horner’s Syndrome • Pupillary Constriction • Ptosis • Flushed & Dry Skin • Loss of Sympathetics • Lesion can be in CNS or PNS • Deficits ipsilateral to lesion Pg. 7-8
- 25. 25 Accommodation (or “Near”)Reflex 1. Initiated by shift in gaze from far to near. 3. Efferent limb: GSE & GVE of Oculomotor Optic nerve Optic tract Lateral Geniculate Nucleus Optic Radiation Primary Visual Cortex Association Visual Cortex Optic Radiation Br. of Superior Colliculus Superior Colliculus Oculomotor Nuclei Oculomotor Nerve Argyll Robertson pupil: Pupillary constriction occurs as part of the accommodation reflex, but not in response to light. 2. Three components: Ocular convergence Pupillary constriction Lens thickening 4. Afferent limb & Central Connections: Pg. 8
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