Ophthalmology > Visual Fields & Visual Cortex > Flashcards

Visual Fields & Visual Cortex Flashcards

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1
Q

What is the retrochiasmal pathway?

A

The retrochiasmal pathway begins posterior to the optic chiasm with the optic tracts then travels to the lateral geniculate nuclei, the temporal lobe optic radiations (i.e., Meyer’s loop), the parietal lobe optic radiations, and ends in the occipital cortex.

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2
Q

What do chiasmal lesions result in?

A

Bitemporal hemianopia (common in pituitary adenoma)

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3
Q

What do retrochiasmal lesions result in?

A

Contralateral homonymous field defect

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4
Q

Why do V1 lesions often result in homonymous hemianopia with macular sparing?

A

Due to dual blood supply of the occipital lobe where the macula is represented

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5
Q

What are the layers of the retina?

A

LIGHT COMES IN:

Inner limiting membrane
Optic Nerve Fibres
Ganglion Cells
Inner Plexiform Layer
(Amacrine)
Inner Nuclear Layer
(Bipolar)
Outer Plexiform Layer
(Horizontal)
Outer Nuclear Layer
(Photoreceptors)
Outer Limiting Membrane
Rods & Cones
Retinal Pigment Epithelium
Brunch’s Membrane

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6
Q

What are the two types of retinal ganglion cells?

A

Parasol & Midget

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7
Q

What are the 4 main parts of the optic nerve and how long are they?

A

Intraocular - 1mm
Intraorbital - 25-30mm
Intracanalicular - 4-10mm
Intracranial - approx. 10mm

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8
Q

What root of the optic tract does the LGN receive information from?

A

The large lateral root & receives fibres from both eyes (as after the optic chiasm)

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9
Q

How many layers of the LGN are there?

A

6

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10
Q

Which layers of the LGN are ipsilateral?

A

2, 3, 5

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11
Q

Which layers of the LGN are contralateral?

A

1, 4, 6

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12
Q

Which layers of the LGN do the magnocellular pathway cells go to?

A

1 - 2

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13
Q

Which layers of the LGN do the parvocellular pathway cells go to?

A

3 - 6

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14
Q

What is the superior colliculus for? What cells travel here?

A

Rapid motor reflexes involving cranial nerves and spinal motor neuronal pathways
Magnocellular

It’s in the small medial root of the optic tract for visual associate pathways like automatic scanning

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15
Q

What do the optic tracts become after the LGN?

A

Optic Radiations

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16
Q

What are the layers of the retina from deep to superficial?

A

1) Inner Limiting Membrane
2) Optic Nerve Fibres
3) Ganglion Cells
4) Inner Plexiform Layer
5) Inner Nuclear Layer
6) Outer Plexiform Layer
7) Outer Nuclear Layer
8) Outer Limiting Membrane
9) Rods & Cones
10) Retinal Pigment Epithelium (Outer Layer)

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17
Q

What is the order of the cells between the retinal layers?

A

1) Amacrine
2) Bipolar
3) Horizontal
4) Photoreceptors

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18
Q

How does the optic nerve travel to the optic chiasm?

A

The optic nerve travels posteriorly and medially to the optic chiasm

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19
Q

What are the two roots of the optic tracts?

A

Large Lateral Root:
90% of fibres, terminate in the LGN for conscious visual perception

Small Medial Root:
10% for everything else - the superior colliculus (visual associate pathways for automatic scanning), pretectal nucleus (light reflex) and the suprachiasmatic nucleus of the hypothalamus (photoperiod regulation)

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20
Q

What is the pretectal nucleus for?

A

It’s in the small medial root of the optic tract and is for the light reflex

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21
Q

What is the suprachiasmatic nucleus of hypothalamus?

A

It’s in the small medial root of the optic tract and is for photoperiod regulation

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22
Q

Where does the upper division of the optic radiations pass?

A

Through the parietal lobe which is a more direct course

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23
Q

What is the upper division of the optic radiations responsible for?

A

Info from the superior retina and thus the inferior visual field

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24
Q

What is the lower division of the optic radiations responsible for?

A

The inferior retinal fibres and thus the superior visual field

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25
Where does the lower division of the optic radiations pass?
It's a less direct route via the temporal lobe. The inferior retinal fibres initially travel anteriorly through the loop of Meyer before travelling posteriorly towards V1
26
What does the occipital cortex do?
Primary integration of shape, colour and motion
27
What does the temporal cortex do?
Higher order integration of recognition and memorisation of objects and forms
28
What does the parietal cortex do?
Higher order integration for precise localisation of animate and inanimate objects
29
How does the pupillary reflex occur?
Temporal retinal ganglion cell axons synapse at the ipsilateral pretectal nucleus and the nasal retinal ganglion cell axons synapse at the contralateral pretectal nucleus The pretectal nuclei then send preganglionic fibres to the Edinger-Westphal nuclei (crossed and uncrossed). Each of the Edinger-Westphal nuclei send preganglionic parasympathetic fibres travelling along CN III through the inferior oblique branch They synapse at the ciliary ganglion where postganglionic parasympathetic fibres travel along the short ciliary nerves to sphincter pupillae muscles for miosis
30
What optic nerve diseases cause RAPD?
MS Ischaemic optic neuropathy Glaucoma - an increase in intraocular pressure that strangulates the nerves Optic nerve compression
31
What retinal diseases cause RAPD?
Ocular ischaemic syndrome Ischaemia (retinal artery occlusion or vein occlusion) Retinal detachment (strangulates nerves as blood supply is unable to get through)
32
What is the frontal eye field pathway?
It's part of the accommodation reflex where afferent fibres go to motor nucelli for eye convergence and to Edinger-Westphal of the CN III for pupil constriction.
33
What is the efferent limb of the accommodation reflex?
Motor nuclei increases output to the medial recti
34
How are the Edinger-Westphal nuclei involved in the accommodation reflex?
The Edinger-Westphal nuclei send parasympathetic fibres that go down the inferior oblique branch of CN III and synapse at the ciliary ganglion. The postganglionic parasympathetic then innervate ciliary muscles and sphincter pupillae causing the lens to thicken and results in Miosis. The Edinger-Westphal work either by the pretectal nucleus (for miosis in response to light) or through the frontal eye field for the accommodation reflex (when an object is at near),
35
What margin is critical for coping in a real environment?
Margin of temporal visual field
36
What does peripheral VF loss correlate well with?
Structural loss like nasal optic disc loss
37
How large is the blind spot and where is it?
- 15 degrees temporal - 2.5 degrees inferior - 5 degrees in diameter
38
How far does the monocular VF extend?
- 160 degrees horizontally - 135 degrees vertically
39
How far does the binocular visual field extend?
- 60 degrees either side of the vertical midline
40
How far do the superior/inferior VF extend?
- 60 degrees superiorly - 75 degrees inferiorly
41
What are some symptoms of eye disease?
- Change in appearance of the eye(s) - Discharge from the eye - Pain and/or discomfort - Loss of vision, or change in quality of vision - Double vision - No symptoms - Pain & Discomfort Severe pain is rare and usually means serious eye disease e.g. acute glaucoma, scleritis Referred pain e.g. migraine, ice cream headache Lesser symptoms are much more common e.g. burning-common in lid disease; itching-common in allergy; gritty and foreign body sensation –common in dry eyes - Loss or a change in quality of vision
42
If a patient reports vision loss, what should you ask them about?
- Transient or continuous - Profound or mild - Rapid or slow onset - Central or peripheral or altitudinal - One or both eyes - Affecting colour, contrast, night vision
43
What are come examples of symptomless disease?
Some important conditions are asymptomatic in the early (treatable) stages e.g. - Chronic glaucoma (tends to be picked up early by optometrist) - Diabetic retinopathy (screening programme for this due to asymptomatic nature of treatable disease that could prevent vision loss) - Hypertension - Papilloedema All will become symptomatic with time (or can indicate serious underlying condition) and therefore should be looked for in susceptible individuals
44
What is a scotoma?
A circumscribed area of loss of vision in the visual field e.g. the normal blind spot
45
What is a hemianopia?
Loss of half of the field of vision with a vertical border
46
What is a Quadrantinopia?
Loss of quarter of the field of vision with a vertical border
47
What is an Altitudinal Defect?
Loss of half of the field of vision with a horizontal border
48
What is Arcuate?
A scotoma that is shaped like an arc of a circle
49
What does Sectoral mean when relating to VFs?
A field defect that is ‘pie-shaped’ and extends from the blind spot
50
What is a homonymous VF defect?
Affecting the same side of the visual field for both eyes E.g. LE can’t see temporal (left) RE can’t see nasal (left) = Left Homonymous Defect
51
What is a bi-temporal VF defect?
Affecting the temporal field of both eyes
52
What is a Centrocaecal Scotomata?
A scotoma that incorporates the blind spot
53
What does confrontation VF test for?
This is only helpful for detecting: - Hemianopias - Altitudinal defects - Large central scotomas
54
When do we use a Goldman (Octopus) field?
Neurological disease
55
When do we use a Humphrey field?
Essential for the management of glaucoma
56
How are VF defects recorded using confrontation, Goldman and Humphreys?
- Confrontation testing produces a description of a defect and a possible sketch in the notes - Goldman testing produces a series of ‘isopters’ rather like contour lines on a map - Humphrey testing produces a grey scale diagram of the defect showing pattern and intensity of defect
57
What VF may an Optic disc infarction in anterior ischaemic optic neuropathy produce?
Sectoral or altitudinal defect
58
What VF defect might an optic neuropathy produce?
May produce central or centrocaecal scotomas
59
What VF does glaucoma produce?
Glaucoma produces a variety of field loss depending upon severity - Nasal step - Then arcuate - Then altitudinal - And finally total peripheral loss
60
How does the optic chiasm run?
At the chiasm, fibres from the nasal retina (temporal field) cross to the opposite optic tract The boundary runs through the centre of the visual field (through the macula) and not through the optic disc
61
Where does the optic chiasm lie and what is it vulnerable to from the pituitary?
- The chiasm lies in the anterior part of the third ventricle - It is 1cm above the pituitary gland Swelling of pituitary = can push into the optic chiasm causing bi-temporal hemianopia as pressing on the nasal fibres from each eye
62
What is a sign of chiasmal compression and how does it occur?
The hallmark of chiasmal compression is a bitemporal hemianopia The nasal crossing fibres in the chiasm are compressed first, which causes loss of temporal field in both eyes
63
What type of VF defect does a pituitary tumour cause?
A pituitary tumour will compress the chiasm from BELOW This will cause damage to inferior fibres first This leads to a bitemporal defect affecting the SUPERIOR field
64
What type of compression on the optic chiasm affects the inferior field progressing to a bitemporal hemianopia?
Craniopharyngioma
65
What is a Craniopharyngioma and what does it cause?
Craniophryngiomas develop above the chiasm Compression therefore affects the inferior visual field and progresses to a bitemporal hemianopia
66
Where do fibres in the optic tracts synapse?
In the LGN below the thalamus
67
What visual defects do you get from lesions to the optic radiations?
Retrochiasmal = behind the chiasm = homonymous VF defect Visual defects from now on affect the same side of vision in both eyes and are therefore homonymous
68
What are Optic Tract Lesions usually caused by?
Usually vascular
69
What would an optic tract lesion look like?
Fibres from the retina which represent the same parts of the visual fields have not yet come together This means that defects are not the same in each eye’s visual field A lesion of the right optic tract will therefore produce a left sided incongruous (affecting right eye more than left) homonymous hemianopia (as shown above)
70
Where are the visual radiations?
From the lateral geniculate nucleus, fibres spread into the parietal and temporal lobes
71
What VF loss do temporal lobe lesions cause?
Superior Field Loss
72
What VF loss do parietal lobe lesions cause?
Parietal lobe lesions affect inferior field
73
What are visual radiation lesions often caused by?
Lesions are vascular or due to space occupying lesions and are accompanied by other neurological defects e.g. hemiplegia
74
What types of lesions are congruous?
Lesions affecting the visual radiations are congruous i.e. the same size in the field from each eye E.g. such as after stroke
75
What would a right posterior cerebral artery occlusion cause?
A left homonymous hemianopia with macular area spared as a result of collateral flow from the middle cerebral artery
76
What VF loss does retinal disease cause?
Retinal disease produces a defect in one eye
77
What VF loss does optic nerve disease cause?
Optic nerve disease produces a central scotoma
78
What does VF loss does chiasmal compression cause?
Chiasmal compression produces a bitemporal hemianopia or a junctional scotoma
79
What VF loss do retrochiasmal lesions cause?
Anything behind the chiasm produces a homonymous hemianopia on the opposite side
80
Which VF lesions are incongruous and which are congruous?
- Tract defects are incongruous - Radiation defects are congruous
81
What causes VF macular sparing defects?
Occipital strokes cause macular sparing defects
82
What is axial proptosis?
Displacement of the eyeball forwards (axial proptosis) e.g. thyroid eye disease
83
What is non-axial proptosis?
Displacement of the eyeball downwards (non-axial proptosis) e.g. lacrimal gland tumour
84
How does the light reflex occur? (Explain the pathway)
- Afferent pathway 1) Light stimulates the retinal ganglionic cells 2) Action potential travels to optic nerve (CN II) 3) Then bilaterally to right and left  lateral geniculate bodies 4) Axons synapse at right and left pre-tectal nuclei in midbrain 5) Then projects to Edinger-Westphal nucleus of oculomotor nerve (CN III) via interneurons - Efferent pathway 6) Action potential passes to the right and left ciliary ganglions via inferior division of oculomotor nerve 7) Enters eye by short ciliary nerves 8) Sphincter pupillae and cillaris muscle contract
85
What is the pathway for the near reflex?
The pretectal nucleus supplies the right and left Edinger-Westphal nuclei So, shining light in one eye causes ipsilateral and contralateral pupil constriction This is known as the consensual light reflex. Afferent pathway Retina --> LGN --> Visual cortex --> Frontal eye field --> oculomotor nuclear --> Edinger Westphal nucleus (bypasses pretectal nuclei) Efferent pathway Parasympathetic fibres Edinger Westphal nucleus --> oculomotor nerve --> right and left ciliary ganglions --> short ciliary nerve --> iris sphincter Some fibres of ON bypass the LGN and go to pre-tectal nucleus at level of Sup colliculus in the midbrain
86
Simply, what structures does the pupil light reflex (parasympathetic) pass?
ON --> pretectal nucleus --> EW nucleus --> Oculomotor nerve --> ciliary ganglion --> short ciliary nerves --> sphincter pupillae
87
What is the Sympathetic chain (dark response) pathway?
Superior cervical ganglion in the sympathetic chain The process starts with the retina and optic tract sending signals to the hypothalamus, which then relays them to sympathetic neurons in the spinal cord and superior cervical ganglion, ultimately causing pupil dilation. 1. Posterior hypothalamus 2. Ciliospinal centre of budge 3. Superior cervical ganglion 4. Ophthalmic Nerve --> Dilator iridis muscle See slide 70
88
If someone has an afferent pupil defect what will we see of their pupil?
Big pupil
89
If someone has an efferent pupil defect what will we see of their pupil?
Small pupil
90
What are afferent pupil defects caused by?
Optic nerve lesions (pupils will be the same size)
91
What are efferent pupil defects caused by?
- Parasympathetic system -Adies pupil, 3rd NP - Sympathetic system - Horners syndrome Pupils will be of different sizes (anisocoria)
92
How to distinguish between Adies pupil and CNIII without pupil sparing?
Aidies pupil is isolated to the pupil only
93
When do we need to do if there's anisocoria seen on a patient?
If there is anisocoria you need to examine RAPD in dark and light to see when it is most obvious – this will tell you which is the abnormal pupil due to the dilation/lack of dilation seen
Ophthalmology
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