Eye And Vision Flashcards

1
Q

What is the visual pathway?

A

Retina- optic nerve- optic chiasm- optic tracts- LGN- optic radiations- primary visual cortex (occipital lobe)

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2
Q

Where does the optic nerve exit the globe?

A

Optic canal

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3
Q

Which fibres cross at the optic chiasm?

A

Nasal fibres

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4
Q

Where is the LGN situated?

A

Near the thalamus

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5
Q

Where do the optic radiations travel?

A

Upper division: direct route through the parietal lobe
Lower division: anteriorly through meyers loop and then posteriorly through the temporal lobe to the visual cortex

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6
Q

Where is the visual cortex?

A

Either side of the calcarine sulcus in the occipital lobe

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7
Q

What percentage of the optic tract terminates at the LGN?

A

90%

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8
Q

Where does the medial route of the optic tract terminate?

A

Superior colliculus- visual association pathways and automatic scanning
Pretectal nucleus- light reflex
Superchiasmatic nucleus of hypothalamus- photoperiod regulation

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9
Q

What is the pupillary reflex?

A

Afferent: retinal ganglion cells to the pretectal nucleus
2 efferent (one for each side): from pretectal nuclei to iris sphincter muscles via the edinger westphal nucleus and ciliary ganglions

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10
Q

What is a consensual reflex?

A

Pupillary reflex in response to light entering the contralateral eye

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11
Q

What is RAPD?

A

Relative afferent pupillary defect
Only the afferent limb of light reflex is affected- efferent is normal
Light shone in affected eye will cause dilation

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12
Q

What are the causes of RAPD?

A

Multiple sclerosis
Ischaemic optic neuropathy
Glaucoma
Optic nerve compression
Ischaemia (rvo, retinal artery occlusion)
Retinal detachment

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13
Q

Do media opacities cause RAPD?

A

No!

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14
Q

What is the accommodation reflex?

A

Afferent: from retinal ganglion cells to visual cortex via the LGN and eventually to the frontal eye field
FEF sends fibres to both motor and edinger westphal nuclei
Efferent: motor nuclei increase output to medial recti to cause bilateral adduction
Edinger-westphal nucleus sends preganglionic parasympathetic fibres which synapse at the ciliary ganglion.
Postganglionic PS fibres innervate ciliary muscles and sphincter pupillae leading to increased lens thickness

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