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Semester 3 (M+M) > Eyes > Flashcards

Eyes Flashcards

1
Q

What is the translation of ‘humor’ with regards to the eye?

A

Chamber (aqueous and vitreous)

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2
Q

What is the name for the gap between the cornea and the sclera?

A

Corneal limbus

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3
Q

How does vit A deficiency affect the eye?

A

Less vit A = Less rhodopsin protein = Night blindness

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4
Q

What is ptosis?

A

Drooping of upper eyelid

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5
Q

In the context of optics what is an aberration?

A

Failure of rays to converge on one focus

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6
Q

Which thalamic nucleus is involved in the visual system?

A

Lateral geniculate (LGN)

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7
Q

How does laser eye surgery work?

A

Burns surface of cornea to change it’s shape

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8
Q

What is another name for eyelids? Where are the two eyelids connected and what fissue seperates them?

A

Palpebrae
Connected at med and lat canthus
Separated by palpebral fissure

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9
Q

What glands run along the inner margin of the eyelids and what is their function?

A

Tarsal glands- Secrete lipid rich product to stop eyelids sticking together

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10
Q

What is the lacrimal caruncle?

A

At the medical cunthus, it secretes gritty deposits which sometimes appear on your eyes in a morning

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11
Q

Which muscle closes the eyelids?

A

Orbicularis oculi (deep to thin layer of skin)

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12
Q

Which muscle raises the upper eyelid?

A

Levator palpebrae superioris

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13
Q

What is the conjunctiva?

A

The epithelium (stratified squamous) which covers the inner surface of the eyelids (palebral conjunctiva). The ocular conjunctiva also covers the ant surface of the eye

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14
Q

What is the cornea made of and what is it’s function?

A

5-7 cells layer of stratified squamous epithelium

It is 2/3 of the eyes total optical power as its curvature reflects light). It has a power of about 43 diopters

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15
Q

What is the function of the lacrimal apparatus?

A

Produces, distributes and removes tears

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16
Q

What is the fornix?

A

The pocket created where the palpebral and ocular conjunctiva meet. The superiolateral fornix contains the ducts from the lacrimal gland, which provides tears and nutrient/ o2 demands for the cells of the cornea

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17
Q

What antibacterial agent is in tears?

A

Lysozyme (antibacterial enzyme)

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18
Q

How are tears removed?

A

Blinking sweeps them to medial canthus (area known as lacrimal lake) > lacrimal caruncle > lacrimal puncta (two small pores) > lacrimal canaliculi > lacrimal sac >nasolacrimal duct > inferior meatus > nasal cavity

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19
Q

What is the choroid?

A

Contains a network of BV’s to nourish retina and other eye cells, pigmented black in humans

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20
Q

What is the macula lutea?

A

Oval shaped, v.yellow pigmented 6mm spot which contains the perifovea which circumscribes the parafovea which circumscribes the fovea (largest cone conc, used for high resolution central vision)

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21
Q

What is the difference between the aqueous humour and the vitreous humour?

A 
Aqueous= Like water, continually replaced
Vitreous= Stagnant gel, produced by secretions of ciliary bodies in vitro. Provides pressure to keep everything in place
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22
Q

What are the ciliary bodies?

A

Ciliary muscles + ciliary processes

Produces aqueous humour and vitreous when in vivo

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23
Q

What are the ciliary processes?

A

Inward folds of the choroid between the suspensory ligaments

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24
Q

What is the sclera?

A

Tough fibrous coating which provides attachments for muscles

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25
Q

What kind of proteins are rhodopsin and photopsin?

A

G-protein coupled receptors

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26
Q

What are the different proteins in rods and cones?

A 
Rods= Rhodopsin
Cones= Photopsin
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27
Q

Why is vitamin A important for sight?

A

Both rhodopsin and photopsin use conversion of retinol (11-cis to 11-trans) to activate cascades
Retinol is a slightly processed version of vitamin A

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28
Q

In a dark environment what is the pathway between the rod cell and the ganglion cell?

A

Rod cell fires (glutamate) which inhibits the bipolar cell so therefore the BP cell does not excite the ganglion cell and the ganglion cell does not fire

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29
Q

What is the visual pathway from rod cell to visual cortex?

A

Rod > bipolar > ganglion > LGN > primary visual cortex

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30
Q

What are each of the area’s V1/ V5 and V8 responsible for in the visual cortex?

A

V1: primary visual cortex, begins processing
V5: detects motion
V8: does colour vision

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31
Q

What is cortical magnification?

A

Areas with small visual fields (fovea) have large areas in the cortex, those with large visual fields have small areas (periphery)

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32
Q

When do fibres of the secondary visual pathway split from those from the primary and where do they go?

A 
Split before reaching LGN, and go to:
Superior colliculus > Eye movements
Hypothalamus > Circadian rhythm 
Pretectum > controls pupil dilation/ constriction  
CORTEX CAN OVERRIDE
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33
Q

What is stereoacuity?

A

Smallest detectable depth distance seen in binocular vision (depth perception)

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34
Q

What is amblyopia?

A

Lazy eye. Affects 1 in 50 children, usual presentation age 4. Due to not enough nerve connections made. Treat with occlusion of good eye (only works to age 7/8)

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35
Q

What is strabismus?

A

(Squint) where the eyes point in different directions, can caused blurred/ doubled vision. Affects 1in20 children before age 5, normal in babies upto 3months.

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36
Q

What is myopia?

A

Short sighted (can’t see far) refractive disease. Affects 1/3 of UK pop. Symptoms often appear around puberty and can progess until late 20’s. Eye grows too long so light focussed just in front of retina. Genetics and lots of close eye work increase risk. Treat with -veD glasses.

37
Q

What are the different severities of myopia?

A

Mild: -0.5 to -3D
Moderate: -3 to -6D
High: >-6D

38
Q

What is hyperopia?

A

Long sightedness (can’t see near), eye too short so light focussed behind retina. Tends to present after age 40. Treat +veD glasses

39
Q

What are the 3 possible causes of hyperopia?

A

Eyeball to short
Lens not thick enough
Cornea not curved enough
All result in light focussed behind retina not on it

40
Q

What is astigmatism?

A

Where the cornea/ lens are not perfectly curved, resulting in incorrect light focussing. Usually present from birth

41
Q

What is the names of the letters on a snellen chart, the only letters used are what type of letter?

A

Letters are called optotypes (standard size and font)

Only the 10 sloan letters used

42
Q

What do 7/6, 6/6 and 6/60 all mean?

A

7/6- Patient has above normal eyesight
6/6- Patient can see at 6m what normal can see at 6m
6/60- P can see at 6m what normal can see at 60m (definition of blind)

43
Q

What is optical power?

A

The degree to which a lens/ mirror/ object converges or diverges light. It is equal to 1/ (the focal length) and is measured in dioptres (inverse meters)

44
Q

What power do converging lenses have? What shape are they and for what eye condition would converging lenses be given?

A

Converging lenses have +ve optical power
They are convex
Given for hyperopia
(normal reading glasses are +1 to +3 dioptre)
Makes light converge more so converge more anterior

45
Q

What power do diverging lenses have? What shape are they and for what eye condition would converging lenses be given?

A

Diverging lenses have -ve optical power
They are concave
Given for myopia
(Typical distance glasses are -1 to -3 dioptre)
Makes light diverge more so converge more posterior

46
Q

What property of lenses allows glasses to be used to correct refractive error?

A

A -0.5 and -2 dioptre lens placed directly in front of each other with have a power of -2.5dpt.
Therefore a patient with a +2 refractive error (short sighted) would be treated with a -2dioptre lens

47
Q

What is the total optical power of the eye?

A

60 dioptre

2/3 from cornea and 1/3 from lens

48
Q

What is the primary position of the eyeball?

A

Look straight ahead

49
Q

What are the secondary positions of the eyeball?

A

Looking up down left or right

50
Q

What are the tertiary positions of the eyeball?

A

Diagonal gaze

51
Q

What is the name for rotation in the vertical axis?

A

Yawing

52
Q

What is the name for rotation in the horizontal axis?

A

Rolling

53
Q

What is the name for rotation in the transverse axis?

A

Pitching

54
Q

All recti muscles acting on the eye pull in which direction?

A

Medially

55
Q

The trochlear nerve (CN IV) supplies which muscle?

A 
Superior oblique (down and out) 
(aka intorsion and depression)
56
Q

The abducens nerve (CN VI) supplies which muscle?

A

Lateral rectus (does abduction- look out)

57
Q

What is the action of the medial rectus muscle?

A

Adduction (look in)

58
Q

What is the action of the superior rectus muscle?

A

Elevation and adduction (look up and in)

59
Q

What is the action of the inferior rectus muscle?

A

Depression and adduction (look down and in)

60
Q

What is the action of the inferior oblique muscle?

A

Look up and out (Elevation + abduction + lat rotation)

61
Q

What does CN III innervate?

A

Somatomotor fibres to LPS, sup/inf/med rectus and inf oblique
PNS fibres to cillary muscles
PNS fibres to constrictor pupilae (circular/ sphincter)

62
Q

Sensory fibres from the eye and other orbital structures are carried by which nerve?

A

Opthalmic (v1) and maxillary (v2) branches of trigeminal nerve

63
Q

PNS fibres to the lacrimal gland are carried by which nerve?

A

Facial (CN VII)

64
Q

What is the annulus of zinn?

A

Oval shaped thickening of periosteum at orbital apex (enclose optic canal and part of sup orbital fissure)
Origin for SR, IR, MR, LR + SO (But not inferior oblique)

65
Q

What are versions?

A

Where eyeballs move in same direction and line of sight remains parallel

66
Q

What are vergences?

A

Where eyes move in different directions and line of sight are not parallel

67
Q

What is the difference between a congruous defect and an incongruous defect? Where does each suggest the pathology lies?

A

Congruous: Both eyes affected the same (problem after LGN)
Incongruous: Different in each eye (Problem before LGN)

68
Q

What are horizontal and amacrine cells?

A

Laterally interconnecting neurons linking rods (or cones), they modify visual signal (eg. amacrine can turn blue off into blue on signals)

69
Q

Which region of your body has the highest blood flow?

A

The choroid

70
Q

Why do pituitary tumours affect vision?

A

Push out of dorsum sellae and press onto optic chiasma (if hormone secreting will prob be found before vision affected)
Any tumours after LGN will not affect pupil (but before such as pituitary could)

71
Q

Which quadrant is often the first one to be affected in an asymmetric pituitary tumour?

A

Superior temporal

72
Q

Unequal pupil constriction when doing the swinging light test indicates what?

A

Lesion between retina and optic chiasm

73
Q

What is deuteranomaly?

A 
A form of colour blindness afecting 5% of the male population.
Defective green (M) cones have a shifted frequency 
(Deuteranopia= loss of green cones)
74
Q

What is trichromacy?

A

Normal colour vision

75
Q

Which type of colour deficiency is most common (including all 4 subtypes) and what is the incidence?

A

Red-Green (Deureranomaly = green, protanomaly = red)

1 in 12 M) (1 in 200 F

76
Q

What is the name for the coloured dotted plates which test colour blindness?

A

Ishihara plates

77
Q

What is the difference between off and on bipolar cells?

A

Off cells have AMPA receptors (excitatory) - In dark they release NT to ganglion cells
On cells have mGluR6 receptors (inhibitory)- In light they release NT to ganglion cells

78
Q

What effect does light have on photoreceptors?

A

It hyper-polarises them

79
Q

What are the three types of cone cells and how do they come about?

A

As three different opsin genes
L (long wave) = RED 564nm
M (medium wave) = GREEN 533nm
S (short wave) = BLUE 433nm

80
Q

What do colour channels do we see in?

A

Red/ green and Blue/ yellow

For colour we do not just judge the presence of light but whether their is contrast between different colours

81
Q

What happens to the lens when viewing near objects?

A

Ciliary muscles contract = suspensory ligaments relax = lens bulges so becomes thicker/ rounder/ more convex = most refractive power

82
Q

What happens to the lens when viewing far away objects?

A

Ciliary muscles relax = suspensory ligaments tighten = lens is pulled more flat/ thin/ less convex = less refractive power

83
Q

Light being received onto which portion of the eye causes a blind spot?

A

Optic disc

84
Q

Why would cylindrical lenses be given?

A

To focus light onto a line not a point

Treat hyperopia- long sightedness

85
Q

What would be an example of neuronal tuning?

A

Certain neurons fire action potentials when a particular stimulus enters their receptive field e.g. a vertical bar of light

86
Q

What is the result of light shining on an opsin molecule on cGMP conc?

A

Activated opsin (cis to trans retinol) = activated transducin = lowered cGMP

87
Q

How is transducin activity terminated?

A

GTPase activity

88
Q

Which brain area, shaped like a bent knee receives feedback from the primary visual cortex?

A

Lateral geniculate nucleus (LGN)

89
Q

A lesion of CN III, CN IV or CN VI will result in the eye being fixed in which direction?

A

CN III- Down and out (As lat rectus and sup oblique dom)
CN IV- No obvious position change at rest
CN VI- Adducted (looking in)- Lost lateral

Semester 3 (M+M) (16 decks)

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