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BRS YEAR 2 > Visual System > Flashcards

Visual System Flashcards

1
Q

Name for the white of the eye

A

Sclera
Has high water content

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2
Q

name for the corner of the eye where eyelids meet?

A

lateral/medial canthus

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3
Q

name for the pink bit in the medial corner?

A

Caruncle

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4
Q

three layers of the eye in order?

A

sclera (hard and opaque) → choroid (pigmented and vascular) → retina (neurosensory tissue)

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5
Q

name for eyeball vascular coat?

A

Uvea

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6
Q

What is the uvea made of

A

choroid, ciliary body, iris (all interconnected)

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7
Q

where is the retina?

A

Inner part of eye

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8
Q

Retina function

A

capturing light rays and turning information into optic nerve signalling

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9
Q

visible portion of the optic nerve is called what?

A

Optic disc

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10
Q

what is the macula responsible for?

A

spot in centre of retina lateral to optic disc responsible for detailed central vision.

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11
Q

name for the spot in the centre of the macula?

A

Fovea
Allows appreciation of fine detail and perform tasks that require central vision such as reading

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12
Q

What does the fovea have the highest concentration of

A

Cone photoreceptors

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13
Q

central vision function vs peripheral vision function?

A

central: detailed day vision, colour, reading, facial recognition.

lacking = poor visual acuity

peripheral: shape, movement, night vision

lacking = poor visual field (can need visual aids even if perfect acuity)

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14
Q
  • layers of the retina → what do they contain?
A

outer layer: photoreceptors (rods and cones) = 1st order neurons

middle layer: bipolar cells (local signal processing) = 2nd order neurons

inner layer: retinal ganglion cells (transmit info to brain) = 3rd order neuron

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15
Q

differences between rods and cones?

A

rods more sensitive to light, slow response, more abundant, do night vision (scotopic) 120 million rods

cones less sensitive with faster response, do day light fine vision and colour vision (photopic) 6 million rods

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16
Q

what happens to light when passing from one medium into another?

A

Velocity changes (refraction)

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17
Q

Two types of lens and their function

A

convex converges light rays to a point

concave spreads light rays outwards

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18
Q

emmetropia vs ametropia?

A

emmetropia = adequate correlation bw axial length and refractive power (parallel light rays fall on retina)

ametropia = mismatch bw axial length and refractive power (parallel light rays don’t fall on retina)

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19
Q

Difference types of ametropia

A

Myopia
Hyperopia
Presbyopia

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20
Q

Myopia

A

parallel rays converge at a point anterior to retina

can be axial → more common or refractive (excessive long globe or excessive refractive power)

Blurred distance vision,squinting and headache

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21
Q

Hyperopia

A

parallel rays would converge at a point posterior to retina

excessive short globe (axial, more common) or insufficient refractive power

visual acuity blurred at near, can be more noticeable at times or when tired

eye pain, headache in frontal region, burning in eyes } = asthenopic symptoms

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22
Q

Near response triad

A

pupillary miosis (contraction, sphincter pupillae) to increase depth of field,convergence (medial recti) to align both eyes towards a near object, accommodation (circular ciliary muscle) → increase lens refractive power and increases lens thickness

  • naturally occuring loss of accommodation in old age
23
Q

what is presbyopia?

A

Naturally occurring loss of accommodation in old age

24
Q

What is presbyopia corrected by

A

reading glasses that increase refractive power
(Convex lenses)

25
retinal ganglion of the optic nerve reach which landmark next?
Optic chiasm Approx 53% of fibres decussate to contralateral optic tract
26
Which fibres decussate at the optic chiasm
those originating from nasal retina (left hand side of left visual field, right hand side of right visual field = temporal visual field) - one eye only
27
lesions anterior to optic chiasm affect what?
One eye only
28
lesions on optic chiasm cause what?
bitemporal hemianopia (temporal visual field fibres from the nasal retina are the ones crossing over)
29
lesions posterior to optic chiasm cause what?
homonymous hemianopia (left half of both eyes gone or right half of both eyes)
30
how does homonymous hemianopia with macular sparing occur?
homonymous hemianopia often due to stroke Central vision preserved as visual cortex area representing macula receives dual blood supply from posterior cerebral arteries of both sides (middle cerebral artery and posterior cerebral artery so adequate perfusion remains if one affected) Damage to the primary visual cortex
31
why is pupil constriction part of the near response triad?
Increases depth of field Decreases glare
32
What nerves constrict and dilate pupils
Constriction by the parasympathetic nerve in CN III which is the oculomotor Dilation due to sympathetic nerve not oculomotor (done via dilator pupillae muscle)
33
pupillary reflex pathway afferent fibres come from where?
Light enters eye and strikes retina (retinal ganglion cells participate) Axons c8nverge it form optic nerve Decussation of fibres at optic chiasm Pupil specific ganglion cells exit at posterior third of optic tract before entering lateral geniculate nucleus Synapse at pretectal nucleus (brainstem) Synapse on edinger westphal nuclei on both sides of the brain
34
afferent pathway synapses where?
Edinger-Westphal nuclei on both sides
35
efferent pathway synapses where?
Ciliary ganglion Edinger Westphalia nucleus receives input from pretectal nucleus Preganglionic parasympathetic fibres travel along oculomotor nerve where they reach cilliary ganglion and synapse Postganglionic fibres leave and travel via shirt ciliary nerves reaching sphincter pupilae
36
direct vs consensual light reflex?
constriction of light-stimulated eye vs constriction of other eye
37
neurological basis of light reflexes
afferent pathway of either single eye stimulates efferent pathway of both eyes
38
right afferent defect creates what pupil response to light?
right fails to constrict, no consensual reflex by left right consensual reflex present when left is lit
39
right efferent defect creates what pupil response to light?
right fails to constrict, consensual reflex by left present no right consensual reflex when left is lit
40
what is the swinging torch test used to determine?
partial or relative damage to an afferent pathway
41
What happens in swinging torch
both pupils constrict when light swings to undamaged side, both paradoxically dilate when swung to damaged side (relative afferent pupillary defect)
42
six extraocular muscles are called what?
lateral rectus, medial rectus, inferior rectus, superior rectus, superior oblique, inferior oblique
43
What does superior oblique and inferior oblique do
SO-down and out (attached high to temporal side) IO-up and out (attached on nasal side)
44
innervation of the muscles?
superior rectus, inferior rectus, medial rectus, inferior oblique, levator palpebrae superioris (lifts eyelid), pupil constriction = III oculomotor superior oblique = IV trochlesr lateral rectus = VI (abducens nerve abducts eye)
45
What is the antero posterior diameter of the eye in adults
24mm
46
Visual pathway retina neurones
First order neurones-rod and cone retinal photoreceptors Second order neurones-retinal bipolar cells where 53% of fibres cross at the midline Third order neurones-retinal ganglion cells-optic tract synapse where lateral geninucleate tract terminates. Then they extend their axons to the primary visual cortex via optic radiations (4th order neurons)
47
Optic chiasm
53% of ganglion fibres cross at the optic chiasm Crossed fibres originating from the nasal retina responsible to temporal visual fields Uncrossed fibres originating from temporal retina are responsible for nasal visual fields Uncrossed
48
Why does Bitemporal hemianopia occur
Caused by enlargement of pituitary gland tumour
49
In dark pupil dilation
Increased light sensitivity by allowing more light into the eye Mediated by sympathetic nerve
50
Relative afferent pupillary defect
Partial response still present when damaged eye stimulated
51
Superior and inferior rectus
Superior attached to eye at 12 o clock and moves eye up Inferior attached at 6 o clock and moves eye down
52
Blind spot
Where optic nerve meets retina Around optic disc No light sensitive cells
53
Damage to what causes homonymous hemianopia with macular sparing
Primary visual cortex due to stroke

BRS YEAR 2 (68 decks)

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