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Neurology > The Eye > Flashcards

The Eye Flashcards

1
Q

Which type of cells are better for night vision? Why?

A

Rods - converge into one single bipolar cell

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2
Q

Which cells are concentrated to the fovea?

A

Cones

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3
Q

What are cones good for?

A

High acuity
Day vision
Colour vision

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4
Q

What is the path of light from the eye to the visual cortex?

A 
Eye
Optic nerve
Optic chiasm
Optic tract
Lateral geniculate nucleus
Optic radiation
Visual cortex
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5
Q

What are the three major functional classes of neurones in the retina?

A

Photoreceptors - made of rods and cones

Interneurones - bipolar, horizontal and amacrine cells

Ganglion cells - magnocellular (M) and parvocellular (P)

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6
Q

Features of magnocellular (M) pathway sensitivity?

  • colour contrast
  • luminance contrast
  • fine detail
  • motion
A
  • colour contrast: none (black and white)
  • luminance contrast: high
  • fine detail: low
  • motion: high
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7
Q

Sensitivity of parvocellular pathway?

  • colour contrast
  • luminance contrast
  • fine detail
  • motion
A
  • colour contrast: yes
  • luminance contrast: low
  • fine detail: high
  • motion: low
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8
Q

What is the function of interneurones?

A

Combine the signals from photoreceptors

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9
Q

What do the ganglion cells do?

A

They are the output cells of the retina

Their axons converge and leave the eye to form the optic nerve

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10
Q

When looking through an ophthalmoscope, where does the optic nerve leave the eye?

A

At the optic disc, slightly medial to the posterior pole of the globe

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11
Q

Which fibres cross in the optic chiasm?

A

Fibres from the nasal retina of each eye

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12
Q

Where do fibres in the right optic tract carry information from? Which visual field?

A

From the right half of each retina

Carry images seen on the left hemifield

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13
Q

Where do fibres in the left optic tract carry information from? Which visual fields?

A

The left half of each retina

Images from the right hemifield

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14
Q

What are the names of the right and left visual fields?

A

Temporal and nasal

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15
Q

Where is the lateral geniculate nucleus?

A

In the thalamus

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16
Q

Where does the LGN receive projections from?

A

The optic tract
Reticular formation
Brainstem
Cortex

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17
Q

What is the magnocellular pathway most important for?

A

Motion and depth

18
Q

What is the parvocellular pathway most important for?

A

Fine detail and colour

19
Q

Where is the primary visual cortex located?

A

Medial aspect of occipital lobe

20
Q

Where can information from the primary visual cortex be relayed to?

A

Secondary visual cortex (V2)

Tertiary visual cortex (V3)

21
Q

How are the visual cortex neurones arranged?

A

Highly organised columns

Fovea has the largest representation compared to peripheral areas

22
Q

What happens to the retina as it develops?

A

Increases in thickness

23
Q

What is the pathway in the pupillary reflex?

A

Axons from retinal ganglion project along optic nerve to pretectal area of midbrain

These cells synapse bilaterally with interneurones and pass to the Edinger-Westphal nucleus

Here, they synapse with preganglionic parasympathetic neurones in the oculomotor nerve

Pre-ganglionic neurones synapse with post-ganglionic parasympathetic pathway in the ciliary ganglion

Innervate the ciliary muscle, causing constriction

24
Q

What allows the consensual pupillary reflex to occur?

A

There are bilateral projections in the Edinger-Westphal nucleus

25
Q

What are the three events that happen in accommodation and which nerve is involved?

A

Convergence of the eye

Constriction of the pupil

Fixation of the lens - brought about by activation of the parasympathetic component to CNIII acting on circumferential muscles of the ciliary body

26
Q

What would damage to the left optic nerve cause?

A

Complete loss of vision in the left eye

27
Q

What would damage to the optic chiasm cause?

A

Compression of nasal hemiretinae of both eyes as these are the ones which cross

Lose temporal vision - non-homonymous bitemporal hemianopia

28
Q

What can cause non-homonymous bitemporal hemianopia?

A

Pituitary tumour compressing the optic chiasm

29
Q

What would a lesion to the right optic tract cause?

A

Damage to right temporal hemiretinae -> loss of right nasal vision
Damage to left nasal hemiretinae -> loss of left temporal field

So lose left half of visual fields in both eyes
-contralateral (left) homonymous hemianopia

30
Q

What can cause damage to the optic tract?

A

Tumour
Infection
Surgery
Stroke

31
Q

Which fibres are found in meyer’s loop?

A

Fibres from inferior retina - vision of upper half

32
Q

Where do fibres from upper and lower retinal quadrants terminate?

A

Upper retinal quadrant (inferior vision) - medial LGN

Lower retinal quadrant - lateral LGN

33
Q

What can damage to upper right optic radiations in the temporal lobe lead to?

A

Loss of vision in the upper left quadrant - left homonymous superior quadrantopia

34
Q

What can cause a superior homonymous quadrantopia?

A

Damage to the right temporal lobe

-vascular occlusion in middle cerebral artery

35
Q

What can damage to the right occipital lobe lead to?

A

Homonymous hemianopia (left)

36
Q

What does macular sparing indicate?

A

A cortical lesion in the contralateral side

37
Q

What changes in visual fields occur in glaucoma?

A

Damage to the optic nerve causing a peripheral visual field defect which is not always noticed

38
Q

What is the path of light from its entry into the eye to rods and cones?

A

Enters through the iris
Focused by the cornea and lens
Traverses the virtuous humour to reach the retina
Regina consists of rods and cones

39
Q

Where do fibres of from the inferior retina pass?

A

Though the temporal lobe by looping around the inferior horn (Meyer’s loop) of the lateral ventricle

40
Q

Where do fibres from the superior retina travel?

A

Back through the parietal lobe to the occipital lobe in the retrolenticular limb of the internal capsule to the visual cortex

Neurology (20 decks)

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