The Retina and Central Visual Pathways Flashcards Preview

Semester 4 - Neuroanatomy & Neuropsychiatry > The Retina and Central Visual Pathways > Flashcards

Flashcards in The Retina and Central Visual Pathways Deck (29):
1

Why does the position of the optic nerve form a 'blind spot' of vision?

there are no photoreceptors located in the area of the optic nerve leaving the retina/eye

2

What is the purpose of the pigmented layer of the reint, and in which population does this pose a potential problem?

prevent excess light reflections within the retina which would negatively affect vision

 

problem for albino population as they lack melanin, which allows excessive scattering of light on their reitna in bright conditions

3

Which type of photoreceptor in the eye are responsible for black and white/low level lighting vision?

Rods

 

(this is the reason we can only detect monochrome colours at night, as the cones are not active)

4

What is the function of the cone photoreceptors in the eye?

Colour Vision

Detailed Vision in Bright Light

5

Which cells of the reitna converge to form the optic nerve?

Ganglion Cells

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6

What is the function of horizontal cells in the retina?

lateral inhibition

 

allows the photoreceptors detecting the brightest light to inhibit neighbouring cells to allow the contract/sharpness of the image to be enhanced

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7

What can be found in the region of the optic disc on the back of the retina?

Optic Nerve

 

Central Vessels of Optic Nerve
(central retinal artery & vein)

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8

What is the functional importance of the fovea of the retina?

highest density of photoreceptors

 

higest area of visual acuity

9

Does the fovea contain a higher density of rod or cone shaped photoreceptors?

Cones

 

(better for high quality images)

10

Other than a high density of photoreceptors, how else if the fovea adapted to perform it role of vision?

thinner retinal layer due to absence of retinal ganglion cell axons

11

What is the underlying pathological process in a detached retina?

detachment of the photoreceptors from the underlying pigmented layer of the retina

12

Identify the following structures seen on fundoscopy

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13

What symptom do patients commonly present with when suffering from Amaurosis Fugax and what is the underlying pathology?

curtain coming down over vision

 

transient monocular blindness believed to be due to microemboli or vasospasm

14

Why can the optic disc appear to be oedematous with raised intracranial pressure?

Optic nerve is connected to the brain and is surrounded by the meningeal layers, which allows any pressure to transmit from the brain along the optic nerve

15

Identify the structures indicated by the red arrows

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16

Which fibres of the optic nerve decussate at the optic chiasm?

Nasal Fibres

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17

What are the two branches of the optic radiations?

Superior Radiation

Inferior Radiation

18

Outline which fibres of the optic nerve are responsible for the temporal and nasal field of vision

Nasal Fibres = Temporal Field of Vision

Temporal Fibres = Nasal Field of Vision

19

How are visual field defects recorded in the medial notes?

named based on the area of visual loss

20

What defect in the visual pathway would lead to a right sided monocular blindness?

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lesion of the right optic nerve (1)

 

e.g. optic sheath meningiomas

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21

What defect in the visual pathway would lead to bitemporal hemianopia?

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lesion at optic chiasm (2)

 

affects both NASAL fibres

 

e.g. pituitary/anterior communicating artery disease

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22

What defect in the visual pathway would lead to left sided homonomous hemianopia?

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lesion of right optic tract (3)

 

affected right temporal and left nasal fibres

 

e.g. vascular stroke/neoplasia

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23

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24

Defect in which area of the visual pathway causes quadrantanopias?

Superior and Inferior Radiations

25

Why do patients suffering a stroke in the occipital lobe (caused by occlusion of the posterior cerebral artery), sometimes present with macula sparing?

Occipital lobe has a dual blood supply from:

  • posterior cerebral artery
  • branch of middle cerebral artery

 

thus, the blood flow can be preserved to the occipital pole which provides central vision

 

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26

Outline the pathway of the pupillary light reflex

Retina Sensory Afferent (via CN II) > pretectal area & lateral geniculate nucleus

 

pretectal synapses with Edinger-Westphal Nucleus (midbrain) > parasympathetic fibres on CN III leave EDN > pass via cillary ganglio > synapse at sphincter pupillae

 

direct and consensual pupilly constriction

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27

What 3 process are involved in the accommodation reflex of the eye?

 

(think 3 C's)

Convergence
(medial rectus muscle)

 

Pupillary Constriction
(constrictor pupillae)

 

Convexity of Lens
(cillary muscle - lens thickening)

28

Outline the nervous pathway involveed in the accommodation reflex

retina > optic nerve > lateral geniculus >

 

communicates with Edinger-Westphal nucleus

 

efferents travel via occulomotor nerve (parasmpathetics) > sphinctor pupillae and medial rectus muscle

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29

Why does the accommodation reflex require the additional involvement of the primary visual cortex and the pupillary light reflex does not?

accommodation refelx requires the eye to focus on a image that is moving towards the face, whereas the light reflex does not involve any image processing in the primary visual cortex