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Systems: Neurology AB > Vision 2 > Flashcards

Vision 2 Flashcards

1
Q

Visual field

A

Everything you see with one eye (including in the periphery)

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2
Q

How is the visual field tested?

A
  • Confrontation test (outpatient screening)

- Automated perimetry

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3
Q

What should visual field testing not be confused with?

A

-Visual acuity testing

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4
Q

How are images of objects in your field of vision formed?

A

Upside down and inverted on your retina

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5
Q

Where do all fibres from the eye pass through?

A

Optic nerve to the optic chiasma

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6
Q

What happens at the optic chiasma?

A

The (medial) nasal fibres cross to the opposite side

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7
Q

What fibres does the optic tract contain?

A
  • Fibres from the (lateral) temporal half of the ipsilateral eye and the crossed over nasal fibres from the contralateral eye
  • This corresponds to all fibres from the opposite half of the visual field
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8
Q

Where do fibres from the optic tract synapse?

A

LGB of the thalamus

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9
Q

What happens after the optic tract synapses?

A

The optic radiation passes behind the internal capsule (retro-lentiform fibres) to reach the primary visual cortex in the occipital lobe (area 17)

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10
Q

What damage do you expect when the right optic nerve is damaged?

A

Blindness right eye

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11
Q

What damage do you expect when the optic chiasma is disrupted in the middle?

A

Bitemporal hemianopia

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12
Q

What damage do you expect if the right optic tract is damaged?

A

Contralateral homonymous hemanopia

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13
Q

What type of damage do you expect if the optic radiation is damaged?

A

Contralateral homonymous hemianopia

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14
Q

What do intrinsic ocular muscles do?

A
  • Control pupil diameter

- Helps alter lens curvature to enables us to see near objects

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15
Q

What do the extrinsic ocular muscles do?

A

Move the eye

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16
Q

What are the 6 extra ocular muscles?

A
  • Medial rectus
  • Lateral rectus
  • Superior rectus
  • Inferior rectus
  • Superior oblique
  • Inferior oblique
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17
Q

Where do the recti muscles arise from?

A

The apex of the orbit from an annular fibrous ring

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18
Q

Where does the superior oblique muscle arise from?

A

The roof (lesser wing of sphenoid) of the orbit posteriorly

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19
Q

Where does the inferior oblique arise from?

A

The floor of the orbit anteriorly

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20
Q

What muscle runs to the superior eyelid?

A

Levator palpebrae superioris

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21
Q

Where do the recti muscles insert anteriorly?

A

Sclera

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22
Q

Where do the oblique muscles insert?

A

Posteriorly

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23
Q

Where does the LPS originate?

A

Roof of orbit

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24
Q

What muscles are supplied by the oculomotor nerve?

A
  • Medial rectus
  • Superior rectus
  • Inferior rectus
  • Inferior oblique
  • Levator palpebrae superioris
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25
Q

What muscle is supplied by the trochlear nerve?

A

Superior oblique

26
Q

What muscle is supplied by the abducent nerve?

A

Lateral rectus

27
Q

What are the actions of the extra ocular muscles influenced by?

A
  • The muscles are attached along the orbital axis and not the optical axis so they pull o the eyeball at an angle. This means a muscle has more than 1 action
  • The oblique muscles are attached to the posterior part of the sclera so they pull the posterior part of the eyeball up/down and the anterior part moves in the opposite direction
28
Q

What is the action of the medial rectus?

A

Adduction

29
Q

What is the action of the lateral rectus?

A

Abduction

30
Q

What are the actions of the superior rectus?

A
  • Elevation
  • Adduction
  • Intorsion
31
Q

What are the actions of the inferior rectus?

A
  • Depression
  • Adduction
  • Extorsion
32
Q

What are the actions of the superior oblique?

A
  • Introsion
  • Depression
  • Abduction
33
Q

What are the acts of the inferior oblique?

A
  • Extorsion
  • Elevation
  • Abduction
34
Q

Strabismus

A
  • Squint

- Misalignment of the eyes

35
Q

Esotropia

A

Manifests convergent squint

36
Q

Exotopia

A

Manifests divergent squint

37
Q

What are the functional consequences of squint?

A
  • Amblyopia

- Diplopia

38
Q

Amblyopia

A
  • Lazy eye
  • Brain suppresses the image of one eye leading to poor vision in that eye without any pathology (correctable in early years using eye patches to stimulate the lazy eye to work)
39
Q

Diplopia

A
  • Double vision

- Usually occurs in squints occurring as a result of nerve palsies

40
Q

What are the 3 intrinsic muscles of the eye?

A
  • Ciliaris muscle
  • Constrictor pupillae
  • Dilator pupillae
41
Q

Where is the ciliaris muscle found?

A

Ciliary body

42
Q

Where is the constrictor pupillae muscle found?

A

In the iris at the pupillary border

43
Q

Where is the dilator pupillae muscle found?

A

Radially running muscle in the iris

44
Q

What innervates the ciliaris muscle?

A

Parasympathetic fibres via oculomotor nerve

45
Q

What innervates the constrictor pupillae muscle?

A

Parasympathetic fibres via oculomotor nerve

46
Q

What innervates the dilator pupillae muscle?

A

Sympathetic fibres from the plexus around the blood vessels

47
Q

What does pathology of innervation of the intrinsic muscles lead to?

A

Pupillary abnormalities

48
Q

What is the ciliaris muscle for?

A

Focussing on near objects

49
Q

What is the pupillary response to increased illumination?

A
  • Parasympathetic

- Both pupils constrict

50
Q

What is the pupillary response to decreased illumination?

A
  • Sympathetic

- Pupils dilate

51
Q

How should the pupillary reflex be elicited?

A
  • Start in a dimly lit room (pupils dilated)
  • Pen torch in front of one eye then check for both pupils constricting (direct and consensual reflex)
  • Swing light to other side and both pupils should remain constricted
52
Q

Describe the afferent limb aspect of the pathway of light reflex.

A
  • Light falls on the retina
  • Impulses travel along the optic nerve, chiasma and tract
  • Fibres destined to activate the pupillary reflex do not go to the LGB, Instead they leave the optic tract to go to the midbrain (IIIn nucleus)
  • Part of the IIIn nucleus is the Edinger-Westphal nucleus for parasympathetic fibres.
  • The pupillary reflex fibres go to the EWN of both sides
53
Q

Describe the efferent limb of the pathway for light reflex.

A
  • From EWN, preganglionic parasympathetic fibres pass through IIIn into orbit
  • Parasympathetic fibres go to and synapse in ciliary ganglion
  • Postganglionic fibres go through short ciliary nerves to constrictor pupillary
  • Pupillary constriction of both sides
54
Q

Abnormal light reflex

A

Pupils look normal but react abnormally to light

55
Q

Anisocoria

A

Different sized pupils

56
Q

Give 2 examples of when anisocoria may occur.

A
  • Horner’s syndrome

- Injury

57
Q

What may cause an absent/abnormal pupillary reflex?

A
  • Any abnormality of the afferent limb/centre/efferent limb of the reflex
  • Diseases of the retina: detachment/degenerations or dystrophies
  • Diseases of the optic nerve: such as in optic neuritis (frequently seen in MS)
  • Diseases of the III cranial nerve (efferent limb)
58
Q

Why should you check pupillary reflex if someone presents with IIIn palsy?

A
  • In IIIn palsy due to a medical cause such as diabetes, there is usually no damage to parasympathetic fibres
  • Therefore if the reflex is absent suspect a cerebral artery aneurysm and treat it as an emergency
59
Q

Ptosis

A

Drooping of the eyelid

60
Q

Anhidrosis

A

Loss of sweating on affected side

61
Q

Miosis

A

Excessive constriction of the pupil

62
Q

What region is sympathetic outflow?

A

Thoracolumbar

Systems: Neurology AB (51 decks)

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