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Year 2 BRS added > Visual System > Flashcards

Visual System Flashcards

1
Q

3 layers of eye coat?

A

Sclera - hard and opaque
Choroid - pigmented and vascular
Retina - neurosensory tissue

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2
Q

Sclera?

A

White of eyes
Tough, opaque, protective outer coat
High water content

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3
Q

Uvea?

A

Vascular coat of eyeballs, most vascular part of eye
Between sclera and retina
Iris, ciliary body and choroid

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4
Q

Retina?

A

Thin layer of tissue, lines inner part of eye
Captures light (which is sent to brain via optic nerve)

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5
Q

Optic nerve?

A

Transmits electrical impulses from retina to brain
Connects to back of eye near macula
Visible portion called “optic disc”

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6
Q

Macula?

A

In centre of retina
Small and highly sensitive, responsible for detailed vision (e.g. reading)
Fovea = centre

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7
Q

Blind spot?

A

Where optic nerve meets retina - no light sensitive cells

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8
Q

Corresponding anatomical landmark for physiological blindspot?

A

Optic disc

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9
Q

Central vision?

A

Focus
Detail day vision, colour vision, reading, facial recognition
Fovea has highest conc. of cone photoreceptors

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10
Q

Central vision assessment?

A

Visual acuity assessment
Loss of fovea vision = poor visual acuity

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11
Q

Peripheral vision?

A

Motion
Shape, movement, night vision, navigation vision

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12
Q

Peripheral vision assessment?

A

Visual field assessment
Extensive loss of visual field = unable to navigate in environment, may need white stick

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13
Q

Retinal outer layer?

A

Photoreceptors - 1st order neuron
Detection of light

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14
Q

Retinal middle layer?

A

Bipolar cells (2nd order neuron)
Local signal processing to improve contrast sensitivity

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15
Q

Retinal inner layer?

A

Retinal ganglion cells (3rd order neuron)
Transmission of signal from eye to brain

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16
Q

Photoreceptor classes

A

Rods - more sensitive to light, slow response, night vision (scotopic vision)

Cones - less sensitive to light, faster response, day light fine vision and colour vision (photopic vision)

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17
Q

2 types of lenses?

A

Convex - brings light to a point

Concave - spreads light outwards

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18
Q

Emmetropia?

A

Adequate correlation between axial length and refractive power
Parallel light falls on retina

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19
Q

Ametropia?

A

Refractive error
Mismatch between axial length and refractive power
Parallel light rays don’t wall on retina

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20
Q

Myopia meaning?

A

Near-sightedness
Parallel rays converge at focal point anterior to ulna

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21
Q

Myopia causes?

A

Excessive long globe (axial myopia)
Excessive refractive power (refractive myopia)

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22
Q

Myopia symptoms?

A

Blurred distant vision
Squint
Headache

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23
Q

Hyperopia meaning?

A

Far-sightedness
Parallel rays converge at focal point posterior to retina

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24
Q

Hyperopia causes?

A

Excessive short globe (axial hyperopia)
Insufficient refractive power (refractive hyperopia)

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25
Hyperopia symptoms?
Visual acuity at near tends to blur relatively early (more noticeable when tired) Eye pain, headaches in frontal region, burning sensation in eyes
26
Near response triad?
Pupillary miosis Convergence Accommodation *adaptation for near vision*
27
Pupillary miosis?
Sphincter pupillae To increase depth of field
28
Convergence?
Medial recti from both eyes To align both eyes towards a near object
29
Accommodation?
Circular ciliary muscle To increase refractive power of lens for near vision
30
Presbyopia
Naturally occurring loss of accommodation (focus for near objects) Onset from age 40 Distant vision intact Corrected by convex lenses for increased accommodation (refractive power)
31
In accommodation, which one of the following events does not take place? A) Relaxation of Circular Ciliary Muscle B) Relaxation of Zonules C) Thickening of Lens D) Increase of Lens Refractive Power
A - relaxation of circular ciliary muscles do NOT relax
32
Which statement is false for Myopia? A) May be associated with large globe B) Light ray converges behind the retina C) May be associated with increased corneal curvature D) Unable to see objects clearly at distance without glasses or other optical correction
B is false
33
Optic chiasm?
Optic nerves from both eyes converge at optic chiasm 53% decussate to contralateral optic tract
34
Visual pathway?
Eye Optic nerve Optic chiasm Optic tract Lateral geniculate nucleus Optic radiation Primary visual cortex or striate cortex
35
Lateral geniculate nucleus?
Relay centre within thalamus Ganglion nerve fibres synapse
36
Optic radiation?
Forms 4th order neurones Relay signal form lateral geniculate ganglion to primary visual cortex
37
Primary visual cortex or striate cortex?
Within occipital lobe Relays to extra-striate cortex (higher visual processing)
38
Visual pathway retina order neurones?
First order - rod and cone retinal photoreceptors Second order - retinal bipolar cells Third order - retinal ganglion cells
39
Retinal ganglion cells?
Optic nerve (CN II) Partial decussation at optic chiasm (53%)
40
Optic chiasm - crossed fibres?
Originating from nasal retina Responsible for temporal visual field
41
Optic chiasm - uncrossed fibres
Originating from temporal retina Responsible for nasal visual field
42
Lesions anterior to optic chiasm?
Affect visual field in one eye only
43
Lesions posterior to optic chiasm?
Right sided lesion - left homonymous hemianopia in both eyes Left sided lesion - right sided hemianopia in both eyes *often due to stroke*
44
Lesion at optic chiasm?
Bitemporal hemianopia Typically caused by enlargement of pit. gland tumour
45
Homonymous hemianopia with macula sparing?
Damage to primary visual cortex (often stroke) Leads to contralateral homonymous hemianopia with macula sparing *Area representing the Macula receives dual blood supply from posterior cerebral arteries from both sides*
46
Pupils in light?
Constriction Decreases glare Increases depth of field Mediated by parasympathetic nerve (within CN III), causes circular muscles to contract
47
Pupils in dark?
Dilatation Increases sensitivity in dark by allowing more light into eye Mediated by sympathetic nerve, causes radial muscles to contract
48
Pupillary reflex - afferent pathway
Pupil-specific ganglion cells exit at posterior third of optic tract Enter lateral geniculate nucleus Synapse at brain stem pretectal nucleus Each eye synapses on Edinger-Westphal nuclei on both sides in brain stem
49
Pupillary reflex - efferent
Edinger-Westphal nucleus -> oculomotor nerve efferent Synapses at ciliary ganglion Short posterior ciliary nerve -> pupillary sphincter
50
Direct pupillary reflex?
Constriction of pupil of the light-stimulated eye
51
Consensual pupillary reflex?
Constriction of pupil of the other eye
52
Neurological basis for consensual and direct pupillary reflex?
Afferent pathway on either side alone will stimulate efferent pathway on both sides
53
Right afferent defect
E.g. damage to optic nerve No pupil constriction in both eyes when right eye is stimulated with light Normal pupil constriction in both eyes when left eye is stimulated with light
54
Right efferent defect?
E.g. damage to right 3rd nerve No right pupil constriction whether right or left eye is stimulated with light Left pupil constricts whether right or left eye is stimulated
55
Relative afferent pupillary defect
Partial pupillary response still present when damaged eye is stimulated, elicited by swinging torch test E.g. if right eye is damaged… *both pupils constrict when light swings to left undamaged side* *both pupils paradoxically dilate when light swings to right damaged side*
56
Cranial nerves that facilitate eye movement?
CN III CN IV CN VI
57
Muscles of eye?
Superior rectus Inferior rectus Lateral rectus Medial rectus Superior oblique Inferior oblique
58
CN III
Innervates all rectus muscles except lateral Innervates inferior oblique
59
Upper eyelid muscles?
From CN III and sympathetic Levator muscles
60
Superior rectus movement and CN?
Elevates, CN III, superior branch
61
Inferior rectus movement and CN?
Depresses, CN III, inferior branch
62
Lateral rectus movement and CN?
Abducts, CN VI
63
Medial rectus movement and CN?
Adducts, CNIII, inferior branch
64
Superior oblique movement and CN?
Depresses and abducts, CN IV Down and out
65
Inferior oblique movement and CN?
Elevates and abducts, CN III, inferior branch Up and out

Year 2 BRS added (13 decks)

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