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Anatomy & Physiology > Eye & Vision > Flashcards

Eye & Vision Flashcards

1
Q

Where is the LGN?

A

In the hypothalamus

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2
Q

What do the optic tracts become after the LGN?

A

Optic radiations

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3
Q

What are the layers of the retina from deep to superficial?

A

1) Inner Limiting Membrane
2) Optic Nerve Fibres
3) Ganglion Cells
4) Inner Plexiform Layer
5) Inner Nuclear Layer
6) Outer Plexiform Layer
7) Outer Nuclear Layer
8) Outer Limiting Membrane
9) Rods & Cones
10) Retinal Pigment Epithelium (Outer Layer)

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4
Q

What is the order of the cells between the retinal layers?

A

1) Amacrine
2) Bipolar
3) Horizontal
4) Photoreceptors

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5
Q

How does the optic nerve travel to the optic chiasm?

A

The optic nerve travels posteriorly and medially to the optic chiasm

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6
Q

What are the two roots of the optic tracts?

A

Large Lateral Root:
90% of fibres, terminate in the LGN for conscious visual perception

Small Medial Root:
10% for everything else - the superior colliculus (visual associate pathways for automatic scanning), pretectal nucleus (light reflex) and the suprachiasmatic nucleus of the hypothalamus (photoperiod regulation)

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7
Q

What is the superior colliculus for?

A

It’s in the small medial root of the optic tract for visual associate pathways like automatic scanning

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8
Q

What is the pretectal nucleus for?

A

It’s in the small medial root of the optic tract and is for the light reflex

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9
Q

What is the suprachiasmatic nucleus of hypothalamus?

A

It’s in the small medial root of the optic tract and is for photoperiod regulation

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10
Q

What is the LGN?

A

A relay station for the visual pathway where they synapse with 3rd order neurons to form optic radiations (1st order = photoreceptors and 2nd order are ganglion)

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11
Q

Where does the upper division of the optic radiations pass?

A

Through the parietal lobe which is a more direct course

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12
Q

What is the upper division of the optic radiations responsible for?

A

Info from the superior retina and thus the inferior visual field

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13
Q

What is the lower division of the optic radiations responsible for?

A

The inferior retinal fibres and thus the superior visual field

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14
Q

Where does the lower division of the optic radiations pass?

A

It’s a less direct route via the temporal lobe. The inferior retinal fibres initially travel anteriorly through the loop of Meyer before travelling posteriorly towards V1

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15
Q

Where is V1?

A

Either side of the calcarine sulcus/fissure which is on the medial surface of the occipital lobe.

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16
Q

What does the occipital cortex do?

A

Primary integration of shape, colour and motion

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17
Q

What does the temporal cortex do?

A

Higher order integration of recognition and memorisation of objects and forms

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18
Q

What does the
parietal cortex do?

A

Higher order integration for precise localisation of animate and inanimate objects

19
Q

Where do the optic radiations synapse in the occipital lobe?

A

Layer 4 of V1

20
Q

What is miosis?

A

Reflex pupillary constriction

21
Q

What is mydriasis?

A

Reflex pupillary dilation

22
Q

What is the direct and consensual reflex?

A

Direct reflex is constriction in response to light entering the ipsilateral eye.
Consensual reflex is constriction in response to light entering the contralateral eye

23
Q

How many types of nuclei does the oculomotor nerve (CN III) have and what are they?

A

2;
Motor nuclei and the parasympathetic nucleus (aka Edinger-Westphal nucleus)

24
Q

Which branch of the CN III innervates the sphincter pupillae and ciliary muscles?

A

The inferior oblique branch

25
Q

How does the pupillary reflex occur?

A

Temporal retinal ganglion cell axons synapse at the ipsilateral pretectal nucleus and the nasal retinal ganglion cell axons synapse at the contralateral pretectal nucleus
The pretectal nuclei then send preganglionic fibres to the Edinger-Westphal nuclei (crossed and uncrossed).
Each of the Edinger-Westphal nuclei send preganglionic parasympathetic fibres travelling along CN III through the inferior oblique branch
They synapse at the ciliary ganglion where postganglionic parasympathetic fibres travel along the short ciliary nerves to sphincter pupillae muscles for miosis

26
Q

What does RAPD stand for?

A

Relative Afferent Pupillary Defect

27
Q

How can we test for RAPD?

A

Swinging Light Test

28
Q

What does the swinging light test test for?

A

RAPD

29
Q

What else can the swinging light test see other than RAPD (sensory issue)?

A

An efferent issue - wont have a consensual reflex

30
Q

What causes RAPD?

A

Asymmetrical retinal or optic nerve pathology

31
Q

What optic nerve diseases cause RAPD?

A

MS
Ischaemic optic neuropathy
Glaucoma - an increase in intraocular pressure that strangulates the nerves
Optic nerve compression

32
Q

What retinal diseases cause RAPD?

A

Ocular ischaemic syndrome
Ischaemia (retinal artery occlusion or vein occlusion)
Retinal detachment (strangulates nerves as blood supply is unable to get through)

33
Q

What is the accommodation reflex?

A

It’s a near reflex to be able to focus on a near object

34
Q

How much is the cornea and lens responsible for in terms of power of accommodation?

A

Cornea - 2/3rds
Lens - 1/3rd

35
Q

What are the 3 parts to the accommodation reflex?

A

Convergence, increased lens thickness and miosis

36
Q

How does the lens become fatter?

A

It becomes fatter for the purpose of increased power for looking at something at near. The ciliary body contracts and the zonules relax.

37
Q

What are the 2 pathways for the accommodation reflex?

A

1) Afferent Sensory Pathway
2) Efferent Limb

38
Q

What is the afferent sensory pathway?

A

It’s part of the accommodation reflex from the retinal ganglion to V1

39
Q

What is the frontal eye field pathway?

A

It’s part of the accommodation reflex where afferent fibres go to motor nucelli for eye convergence and to Edinger-Westphal of the CN III for pupil constriction.

40
Q

What is the efferent limb of the accommodation reflex?

A

Motor nuclei increases output to the medial recti

41
Q

How are the Edinger-Westphal nuclei involved in the accommodation reflex?

A

The Edinger-Westphal nuclei send parasympathetic fibres that go down the inferior oblique branch of CN III and synapse at the ciliary ganglion. The postganglionic parasympathetic then innervate ciliary muscles and sphincter pupillae causing the lens to thicken and results in Miosis. The Edinger-Westphal work either by the pretectal nucleus (for miosis in response to light) or through the frontal eye field for the accommodation reflex (when an object is at near),

42
Q

What is an astigmatism?

A

Irregular corneal curvature thus resulting in different focal points on the retina

43
Q

How is an astigmatism corrected?

A

Using cylindrical lenses that only have power along one meridian

44
Q

What are the types of astigmatism?

A

Regular Astigmatism - the steepest and least steep meridians are at 90 or 180 degrees.
With the Rule = in kids = steepest meridian is vertical
Against the rule = in elderly = steepest meridian horizontal

Irregular Astigmatism e.g. keratoconus = steepest and least steep aren’t perpendicular

Anatomy & Physiology (13 decks)

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