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Neuro-optometry > Lecture 3: Afferent Visual System and Visual Fields > Flashcards

Lecture 3: Afferent Visual System and Visual Fields Flashcards

1
Q

Visual field is represented in the retina __ and __

A
  • Upside down and reversed
    • Superior field is represented by inferior retina
    • Nasal field is represented by temporal retina
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2
Q

What is the approximate extent monocular VF?

Nasal

Superior

Inferior

Temporal

Temporal blind spot

A
  • Nasal 60 degrees
  • Superior 60 degrees
  • Inferior 70-75 degrees
  • Temporal 100-110 degrees
  • Temporal blind spot (nasal optic nerve)
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3
Q

What is the extent of the binocular visual field

A
  • approximately 180 degrees
  • No blind spots!
  • Stereo!
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4
Q

Interpreting the VF

A
  • Place the fields side-by-side
  • Place right field on your right
    • You appreciate pt’s view point
  • Interpret fields as a pair
    • Look for normal blind spots
    • Look for reliability
    • Look for general depression
    • Look for patterns!
  • Pre-chiasmal vs. Post-chiasmal
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5
Q

List the 13 classification of VF loss?

A
  • Density (severity)
    • Relative: depressed sensitivity
    • Absolute: no visual sensitivity
  • Area
    • Local-areas of the field are affected
    • General - entire field affected
  • Extent
    • Total (total hemianopia)
    • Partial (partial hemianopia)
    • Macular sparing/splitting
  • Shape
    • Sectorial (hemianopic or quadrantanopic)
    • Non sectorial (regular or irregular shaped)
  • Type
    • Scotomatous (enclosed seeing areas)
    • Non-scotomatous
  • Position
    • Which quadrants are affected?
      • Superior-nasal, or inferior-temporal
  • Location
    • Central
    • Peripheral
  • Size
    • Large
    • Small
  • Laterality
    • Unilateral or bilateral
    • Homonymous, heteronymous
  • Equalness
    • Congruous
      • similarity in defect between the 2 eyes
    • Incongruous
      • The defect is not similar between the 2 eyes
  • Awareness
    • Positive
      • The pt is aware of the field loss
      • Negative
    • Cause
      • Organic
      • Functional
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6
Q

Dividing the visual pathways into what 4 territories?

A
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7
Q

What is territory 1?

A
  • Outer retina and choroid
    • Monocular VF affected
    • Not localized to a fiber bundle (horizontal midline)
    • Does not respect the vertical midline
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8
Q

What is territory 2?

A
  • Includes
    • Ganglion cell layer
    • NFL
    • Optic nerve
  • Corresponds to the distribution of the nerve fiber layer
  • Defect appear above or below the midline.. think glaucoma
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9
Q

Schematic representation of the NFL

A
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10
Q

Describe the blood supply to the laminar optic nerve

A
  • Retinal vasculature supplies
    • Surface NFL
  • Short Posterior Ciliary Arteries feed
    • Circle of Zinn-Haller
      • Which supplies:
        • Pre-laminar ONH
        • Laminar ONH
  • Acute obstruction of the branches of short posterior ciliary arteries that supply the
    • Pre-laminar optic nerve
    • Laminar optic nerve
      • Cause disc edema
        • Subsequent atrophy
        • Common in elderly
        • Anterior ischemic optic neuropathy (AION)
        • Typical visual field loss is altitudinal
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11
Q

What occurs if there stasis of axoplasmic flow?

A
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12
Q

Study the image

A
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13
Q

Study the image

A
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14
Q

What does this image show?

A

Papilledema

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15
Q

Describe orbital optic nerve

A
  • Describes nerve from globe to optic foramen
    • 20 mm long
    • Redundant to accommodate mvmt
    • Diameter of the nerve doubles
      • Myelin sheath
  • Papillo-macular fibers migrate into the center of the nerve
    • Superior and inferior fiber fill the space left by papillo-macular fibers
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16
Q

Retrobulbar optic nerve

A
  • Location of the retinal nerve fiber bundles within the retrobulbar nerve
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17
Q

Describe optic nerve disease and VF loss

A
  • Glaucoma
    • Paracentral, arcuate, nasal step, temporal wedge
  • AION
    • Segmental, usu inferior altitudinal
  • Optic neuritis
    • Macular fibers primarily affected - central or centrocecal scotomas, arcuate defects
  • Toxic/Nutritional and Hereditary
    • Central and centrocecal
  • Inflammation behind the globe
    • Retrobulbar
    • Pt sees nothing and the doctor sees nothing
  • Compressive masses
    • Nerve fiber defects breaking through into the periphery
    • Most common optic nerve retrobulbar masses are gliomas and meningiomas
    • Intra-orbital tumors cause non-pulsatile proptosis
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18
Q

intracanalicular portion is accompanied by…? (3)

A
  • Enters the optic canal at the apex of the orbit
  • Optic nerve (CN II) is within optic canal
  • Accompanied only by
    • Ophthalmic artery
    • Meningeal sheaths of the optic nerve
    • Sympathetic twigs
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19
Q

Describe the middle cranial activity? What is adjacent to it?

A
  • Enters the middle cranial cavity
  • Adjacent to its the superior orbital fissure
    • Superior orbital fissure brings
      • CN III
      • CN IV
      • CN VI
      • CN V1
      • Ophthalmic vein to and from globe
    • MR, LR and SR muscles can experience pain from inflammation in this area
    • Mass lesion in this area leads to multiple neurological issues
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20
Q

Describe the intracranial optic nerve

A
  • Extends from optic canal to chiasm
    • 10 mm long
    • Frontal lobes are located superiorly
    • Internal carotids are located laterally
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21
Q

Describe intracranial optic nerve tumors

A
  • Optic nerve gliomas and meningiomas
    • In this region and if large enough may disturb hypothalamic and pituitary function
    • Meningiomas originate from optic nerve sheath arachnoid cap cells
    • Gliomas are slow growing pilocytic astrocytic neoplasms associated with neurofibromatosis
      • Usu benign but can transform into malignancy
      • Larger tumors are disruptive due to mass effect
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22
Q

Intracranial optic nerve lesions affect __ field

A

one

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23
Q

Describe (4) frontal cortex lesions

A
  • Left cortex
    • Broca’s aphasia
      • difficulty with speech
      • Understand speech well
    • Upper motor neuron motor weakness
      • Contralateral
      • Depends on homunculus
    • Frontal eye fields affected
      • If irriated: looks away from the side with the lesion
      • If destroyed: looks toward the side with the lesion
    • Personality and behavior abnormalities
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24
Q

Describe territory 3: optic chiasm

A
  • The optic nerves project backwards and upwards
  • The optic nerves converge and meet over the sella turcica
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25
Sagittal sections and superior views the sellar region showing the optic and chiasm and the carotid artery. The prefixed chiasm is located __ the tuberculum. The normal chiasm is located ___ the diaphragma. The postfixed chiasm is located __ the dorsum
* above * above * above
26
Describe optic chiasm
* Inferior/superior orientation of fibers are maintained * Nasal fibers cross completely * Inferior nasal axons loop anteriorly into the contralateral nerve before turning posteriorly again * Anterior knee of **von Willebrand**
27
Describe chiasmal lesion visual fields
* Tumor extending upwards from sella turcica compresses inferiorly crossing nerve fibers * Superior fields more densely affected * Bi-temporal hemianopia * Eventually may involve CN III, IV, V, VI and VII if tumor is large * Usu due to pituitary tumor * Pituitary adenoma * Tumor must extend at lest **10mm** * Presents with neuro-endocrine signs
28
What does anterior pituitary and posterior pituitary release?
29
What does this image show? What type of VF defect does it cause?
30
Describe chiasmal lesions
31
What are the 4 other causes of chiasmal type of VF defects?
* **Increased Intracranial Pressure (ICP)** * **​**Chiasm lies on the inferior and anterior floor of the 3rd ventricle * Can create a chiasmal type VF loss (bitemporal hemanopsia) * Papilledema will be present * **Aneurysms** * **​**Of the anterior cerebral and anterior communicate arteries * Most likely will be accompanied by HA * **Craniopharyngiomas** * **​**Craniopharyngiomas are cysts that arise from Rathke's pouch * Rathke's pouch is the embryological ectoderm that gives rise to the anterior ptiuitary * Small remanant of this pouch can remain and give rise to a cyst * Aka Ratheke's cyst * **Tilted Disc Syndrome** * **​**Bilateral inferonasal tilting of the optic disc * Associated with high myopia * Bitemporal VF defects are present
32
Describe craniopharyngiomas
* Craniopharyngiomas are derived from remnants of the raniopharyngeal duct (narrow hich separates Rathke's puch from the primitive oral cavity) and can occur anywhere along the infundibulum (from floor of the thrid ventricle, to the pituitary gland) * There is bimodal distribution, with the first peak of onset between the ages **10-14** years and teh second peak in the **7th decade**
33
Describe tilted disc syndrome * What type of VF defects does it produce? (4)
* Cause **pseudo bi-temporal hemianopsia** * Tilted disc may present with different visual field defects * Superior-temporal * Altitudinal * Enlarged blind spot * Bi-temporal hemaniopsia * Tilted disc may mimic "bitemporal hemianopsia" * Bilateral titled disc may show a denser lesion superior temporally that does not respect that midline * Chiasmal lesions that show bitemporal hemianopia that respect the vertical midline * Chiasmal lesions will show papilledema and other associated symptoms
34
Tilted disc may mimic/confound the diagnosis of glaucoma.. how?
* May mimic tempora wedge/arcuate field loss * Visual field defect from tilted dics do not progress * OCT of the NFL unreliable * **Repeat VF with a -4.00D correction over their RX**
35
What does this image show?
* Tilted (oblique) on the right * Vs. normal insertion
36
Describe inferior nasal fibers
* Lesion where the optic nerve first meets the chiasm * Junction of the nerve and chiasm * Central scotoma of the ipsilateral field (poor vision) * Superior temporal scotoma in the contralateral field due to crossing nasal fibers * Nasal fibers crossing into the center of the nerve * _Central scotoma_ in the **ipsi** eye, _inferior fibers_ **contra** eye
37
What type of visual field loss does this image show?
* Junctional scotoma
38
What is the most common type of tumor to cause **junctional scotoma** in middle aged women?
Meningioma
39
What are the 4 post-chiasmal pathway?
* Optic tract * Lateral geniculate nucelus (LGN) * Visual radiations * Visual cortex * Homonymous VF defect * Does not cross the vertical midline
40
What type of VF defect occurs with optic tract lesion?
* Incongruous homonymous hemianopia * VF defect & APD in opposite eye/side * Left hemianopsia * Lesion is on the brain right side with an APD in the LEFT eye
41
Optic Tract: APD in the ___ eye to the lesion, will be in the eye with the ___ VF loss!
* opposite, temporal * Temporal pallor of the optic nerve on the affected side * Bow tie atrophy of the optic nerve of the contra-lateral eye * LGN damge produces similar defects * **Because the nasal fibers also carry the papillomacular bundle**
42
What does this image represent?
Bow-tie and temporal atrophy
43
Study the image
44
What happens if the lesion of the optic tract is closer to LGN?
* Pupillo-motor fibers leave the optic tract anterior to the LGN midbrain nuceli * No APD * Can have normal pupils with massive destruction behind the LGN! * LGN field defects extremely rare * Lesion are typically homonymous and incongruous * Visual fields become more congruous as you get closer to the occipital lobe
45
Describe optic radiations
* From LGN to visual cortex * Through temporal, parietal and occipital lobes * To Brodmann's area 17 (primary visual cortex)
46
What is meyer's loop?
47
Inferior fibers lie __ to the superior fibers, inferior fibers form __ \_\_
* Inferior fibers lie **lateral** to superior fibers * Inferior fibers form meyer's loop * Longer pathway of inferior fibers more susceptible to damage
48
What occurs in a temporal left lobe lesion? (2)
* Difficutly hearing language * Wernicke's Aphasia
49
What occurs with a right lobe temporal lesion? (3)
* Difficulty hearing sounds * Difficulty with rhythm * Difficulty with music
50
What occurs if both temporal lobe lesions are affected? (4)
* Learning/memory difficulties * Olfactory and auditory hallucinations * Complex partial seizures * **Bell's reflex is abnormal** * **​**conjugate deviation away from the side with the lesion when trying to induce normal bell's phenomenon
51
What is the typical VF defect for lesions at the temporal lobe?
* Typical VF defect is a homonymous superior quadrantanopsia * Wedge shaped * Respect vertical midline * "**pie-in-the-sky"** * Visual fields are the PITS
52
What type of VF defect would this lesion produce?
53
Describe what type of VF defect would occur with a lesion at the parietal lobe?
* "**pie-on-the-floor"** * Macular splitting more common * Most common causes are CVA and tumors
54
this image shows a lesion in the __ \_\_
* Parietal lobe lesion
55
Gerstmann syndrome (tetrad) is caused by damage in the __ \_\_ .
* **Parietal lobe** * Left- right confusion * Finger agnosia * Acalcula * Agraphia
56
Right parietal lobe lesion can cause what? (5)
* Sensory abnormality * Astereognosis: 3D integration occurs in parietal lobe * Agraphesthesia * Topographical agnosia * Hemi-neglect anosagnosia
57
Parietal lobe lesions can cause..? (4)
* Abnormal OKN and smooth pursuits * Focal sensory seizures * Riddoch phenomenon * Able to see small kinetic targets better than large static targets * Seen in **occipital lobe** lesions * **bell's reflex is abnormal** * **​**conjugate deviatio AWAY from lesion
58
What are the 3 **eloquent** areas of the cortex? Describe each
* **Broca's area in frontal cortex** * **​**Broca's aphasia * "Nothing gets out" * Wernicke's area in temporal cortex * Wernicke's aphasia * "Nothing gets in" * _Conduction aphasia_ * _​_Damage to arcuate fasciculus that connects * Broca's and Wernicke's area * Paraphrasic speech * Normal understanding * Great difficulty with repeating speech * Gerstmann's area in parietal cortex * Damage to angular gyrus * Agraphia or dysgraphia * Acalcula or dyscalcula * Inability to differentiate left from right * Finger agnosia
59
What type of visual field defect occurs with a lesion at the occipital lobe
* Highly congruent VF * Large macular representation in occipital lobe * Most common lesion is caused by stroke * Most common finding is macular splitting * **Macular sparing** * **​**Dual blood supply to the occipital lobe * Middle cerebral artery (MCA) * Posterior cerebral artery (PCA) controversial: some literature says sparing is caused by poor fixation
60
Study the image
61
Study the image
62
Study the image
63
List 4 important things about macular sparing
64
What type of VF loss would this lesion cause?
65
What occurs in a bilateral occipital lobe lesion? (3)
* Cortical blindness (MCA and PCA blood supply) * Preserved pupil reflex * Anton's syndrome (denial of blindness)
66
What occurs in a right occipital lobe lesion?
* Visual distortion - micropsia and macropsia (alice in wonderland syndrome) * Either lobe may cause visual hallucinations (unformed hallucinations)
67
What occurs in a right lobe occipital temporal lesion? (2)
* Propsagnosia (cannot recognize familar faces) * Geographic agnosia (streets and familiar places)
68
What occurs in a left lobe inferior occipital temporal lesion?
* Visual agnosia of objects * Pure alexia without agraphia (cant read but can write)
69
Study the image
70
Study the image

Neuro-optometry (3 decks)

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