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Nervous System And Neuropsychiatry > Session 4: The Eye > Flashcards

Session 4: The Eye Flashcards

1
Q

What is the function of sensory cells in the retina?

A

Synapse with bipolar cells which synapse with the axon of ganglia which run off to form the optic nerve

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2
Q

What is the function of melanin in the retina?

A

Prevents increased refraction. Lack of melanin such as albinism results in increased reflection in the eye

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3
Q

What is the function of horizontal cells in the retina?

A

Involved in lateral vison. Prevent receptor near the centre of vision sending off consuming impulses for vision

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4
Q

What is the function of the macular in the retina?

A
  • Area of vision in the centre of the optic disc.

- The fovea is found in the macula and is the area of highest concentration of cone cells

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5
Q

What is the function of the rods in the retina?

A
  • Rods are involved in black and white vision.

- They are involved in low light vision

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6
Q

What is the function of the cones in the retina?

A
  • Cones are for high visual acuity and discerning details.

- Cones are used for central vision and detail

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7
Q

What can be seen on fundoscopy?

A
  • Retinopathies
  • Vascular occlusions
  • Macula
  • Optic disc
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8
Q

What is the visual pathway of?

A
  • Temporal fibres run ipsilateral
  • Nasal fibres decussate at the optic chiasm
  • Optic tract runs to the lateral geniculate nucleus
  • Optic radiation split into superior and inferior which runs to the primary visual cortex
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9
Q

What are the visual field and what is responsible for them?

A
  • Nasal fibres are responsible or our temporal field of vision
  • Temporal fibres are responsible for our nasal field of vision
  • Lesions at any point in the pathway will correspond to a pattern of visual loss
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10
Q

What is the overview of the visual field defects?

A
  • Before the optic chiasm, signs are unilateral and ipsilateral
  • At or after the optic chiasm signs are bilateral
  • After the optic chiasm signs will be bilateral and contralateral
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11
Q

What is monocular blindness?

A
  • Caused by a lesion of the optic nerve (right)
  • Optic nerve glioma or retinoblastoma (children)
  • Optic sheath meningiomas (middle aged)
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12
Q

What is bitemporal hemianopia?

A
  • Tunnel vision
  • Lesion at the optic chiasm
  • Affect both nasal fibres therefore both temporal fields lost
  • Caused by surrounding structures. Pituitary gland and anterior communicating artery for example
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13
Q

What is left homonymous hemianopia?

A
  • Lesion of the right optic tract

- Affect the right temporal and left nasal fibres

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14
Q

What is right homonymous hemianopia?

A
  • Lesion of the left optic tract

- Affecting left temporal and right nasal fibres

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15
Q

What causes left and right homonymous hemianopia?

A
  • Vascular causes are the most common such as a stroke

- Also neoplasia and trauma

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16
Q

What is the blood supply of the occipital lobe?

A

Dual blood supply

  • Posterior cerebral artery
  • Middle cerebral artery (occipital pole)
17
Q

What is macular sparing?

A
  • Occurs in Posterior cerebral artery stroke
  • Most of occipital lobe will be lost
  • However, middle cerebral supplies the occipital pole (represents the macula).
  • Therefore, macular function (central vision) will be spared
18
Q

Whats the important of the macular area?

A
  • Responsible for central vision

- Has a large cortical representation

19
Q

What is the light reflex?

A
  • Light stimulates the afferent nerve in the pathway in CN II
  • Synapses in pretectal area
  • Gives rise to neurones supplying Edinger Westphal nuclei bilaterally
  • Both CN III are stimulated to cause direct and consensual pupillary constriction. Travel along Parasympathetic fibres
20
Q

What are the 3 aspects of the accommodation reflex?

A
  • Convergence (medial rectus)
  • Pupillary constriction (constrictor pupillae)
  • Convexity of the lens to increase refractive power (ciliary muscle)
21
Q

What is the accommodation reflex?

A
  • Near vision
  • Cerebral cortex must be involved because it is relating to image analysis
  • Therefore, the reflex follows the visual pathway via the lateral geniculate nucleus to the visual cortex
  • Final aspect of the pathway is common with the light reflex via EWN
22
Q

What is internuclear opthalmaplegia?

A
  • Defect in the medial longitudinal fasciculus
  • Muscles of the eye cannot communicate with each other as a result
  • Disorder of conjugate lateral gaze in which the affected eye shows impairment of adduction
  • Can be affected by multiple sclerosis

Nervous System And Neuropsychiatry (20 decks)

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