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B3 CAI > Visual Pathway > Flashcards

Visual Pathway Flashcards

1
Q

What three layers is the eyeball composed of?

A

Superficial to deep:

  1. Sclera (outer white layer).
  2. Choroid (vascular).
  3. Retina (neural layer containing photoreceptor cells).
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2
Q

Central retinal vasculature enters the eye at the ?

A

papilla

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3
Q

Why is the papilla a blind spot?

A

There is no retinal tissue as the optic nerve splits here.

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4
Q

Central retinal arterial occlusion can cause ?

A

blindness

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5
Q

Fundoscopy allows for examination of what?

A

Retina.

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6
Q

What is the fovea centralis?

A

The region of greatest visual acuity (sharpest and most detailed vision).

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7
Q

The optic disc is especially vulnerable to what?

A

Changes in pressure - raised ICP can cause swelling of the optic disc.

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8
Q

Does the optic nerve have meningeal coverings?

A

Yes. It is covered by all 3 layers of meninges: the pia, the arachnoid and the dura mater.

Has a subarachnoid space filled with CSF.

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9
Q

What is papilloedema?

A

Swollen optic nerve head due to raised ICP.

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10
Q

The Optic nerve travels from the back of the eye, through the ?, along an ? pathway.

A

optic canal, intracranial visual

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11
Q

What does pupillary light reflex test the functioning of?

A

midbrain, CN II and CNIII

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12
Q

Should both pupils contract if you shine a light in one eye?

A

Yes (consensual light reflex)

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13
Q

Lateral Geniculate Nucleus is part of the ?

A

thalamus

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14
Q

What does the accommodation reflex allow us to do? How?

A

Focus on objects.

Adjusts the shape of the lens in the eye to increase its convexity for near vision.

Also needs to change the size of pupils.

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15
Q

Primary visual cortex is in the ?. From visual cortex, sends information to other areas of the cortex e.g. frontal eye fields.

A

occipital lobe

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16
Q

CN III nucleus is a ? nucleus, Edinger-Westphal nucleus is a ? nucleus.

A

motor, parasympathetic

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17
Q

What muscle is involved in pupil constriction?

A

Sphincter pupillae.

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18
Q

What is the ciliary body?

A

Circular muscle with small ‘strings’ that attach to the lens.

When the ciliary body contracts, tension on the fibres is relaxed - allows lens to ‘puff up’.

Innervated by nerves arising from the ciliary ganglion, under control of EWN.

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19
Q

What are the three things that allow accommodation?

A
  1. Vergence.
  2. Pupillary constriction.
  3. Lens fattening.
20
Q

From who’s perspective is a visual field defect map drawn?

A

Patient’s perspective.

21
Q

On a visual defect map, defects are typically drawn in what colour, indicating they do not have vision in these areas.

A

black

22
Q

Outline how you’d test a patient’s visual field.

A
  • Confrontation with patient staring directly ahead.
  • Typically 1 m away.
  • Cover one eye and patient covers eye directly opposite your covered eye.
  • Tell patient to continue looking at you through the examination.
  • Present a red target at a point equidistant between yourself and the patient.
  • Bring the red pin inwards in the direction of the blue arrows.
  • Ask patient to alert you when they first see the target and see it as red.
  • Compare the patient’s visual field against yours.
23
Q

How is each eye divided during a visual field examination?

A

Each eye has an upper and lower and a right and left quadrant.

24
Q

Why is it important to show the patient a red target during a visual field test?

A

If the patient sees a dull or pale red suggests colour desaturation which may indicate an optic nerve dysfunction.

25
Q

Optic radiation fibres have an upper and lower portion. What are they?

A
  • Lower portion is Meyer’s Loop.

Inferior bundle that arches down into the Temporal lobe.

  • Upper portion is Baum’s Loop.

Superior bundle that arches upwards into Parietal Lobe.

26
Q

Information from the left half of the visual field for each eye ends up on what side of the retina?

A

The right side for each eye.

27
Q

What are retinal fields?

A

The region of retina that is named according to its position relative to the nose or temporal (anatomical) region.

28
Q

Are retinal fields the same as visual fields?

A

No

29
Q

At the optic chiasm, do fibres cross over or stay ipsilateral?

A

Temporal visual field fibres stay ipsilateral, nasal visual field fibres are contralateral.

Optic tract (after optic chiasm) contains visual field fibres from the opposite side only.

30
Q

Where does the optic tract travel to?

A

The lateral geniculate nucleus (in the thalamus) on both sides.

From there, sends off optic radiations (superior and inferior bundles of fibres).

31
Q

Both optic radiations eventually move back to the ? of the occipital lobe.

A

calcarine sulcus

32
Q

Overall, information from the left side of your visual fields ends up on the ? side of your brain and ?.

A

right, upside down

33
Q

Baum’s loop carries the ? visual field portion of the optic radiation, Meyer’s loop carries the ? visual field portion of the optic radiation.

A

lower, upper

(The image shows processing of right visual field information with left optic radiation)

34
Q

Where is the occipital pole?

A

Tip of the striate area of the occipital lobe.

35
Q

What is central macula and where is it processed?

A

Vision that comes from the fovea (area at the back of the eye that receives the highest acuity image).

Processed at the occipital pole.

36
Q

If you damage your occipital pole you can damage your ?

A

central macula vision

= central scotoma

37
Q

What is central scotoma?

A

Visual field defect in the centre of your vision - most detailed vision (loss of macula vision caused by damage to occipital pole).

38
Q

Vascular lesions of the occipital lobe (primary visual cortex) can damage the top and bottom visual fields on the same side. What is this called?

A

Homonymous Hemianopia.

39
Q

What is a homonymous macular sparing hemianopia?

A

Macula is spared because the tip of the striate area (occipital pole) receives a different blood supply to the rest of the occipital cortex.

40
Q

Lesion at the optic chiasm can happen due to an ? or by a ?

A

interpeduncular fossa tumour, large pituitary tumour

41
Q

Everything that is ‘seen’ by the eye is ? and ? as it passes through the lens of the eye. What is seen in your left visual field will be processed by the ? side of your retina.

A

inverted
flipped
right

42
Q

Raised ICP can lead to ? from retinal cells, along the optic nerve. This can cause the nerve fibres to swell up which can cause ? and ? congestion of the blood supply (compromising blood supply to the retina).

A

obstructed flow
capillary
venous

43
Q

Where do fibres from the retinal cell come together and into the optic nerve?

A

optic papilla

44
Q

What does the pupillary light reflex allow us to do?

A

Control the diameter of the pupil, in response to the intensity of light that falls on the retinal ganglion cells of the retina.

A greater intensity of light causes the pupil to constrict (miosis/myosis; thereby allowing less light in), whereas a lower intensity of light causes the pupil to dilate (mydriasis, expansion; thereby allowing more light in).

45
Q

Label the areas that the arrows are pointing to

A
46
Q

Draw each of the visual defects from the patient’s POV

A

B3 CAI (13 decks)

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