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CNS > Lab > Flashcards

Lab Flashcards

1
Q

Presbyopia

A

Denaturation of lens proteins causes a reduction in accommodation hence the near point (the nearest point of distinct vision) recedes throughout life

loss of transparency and increasing hardness of the lens

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2
Q

Visual acuity

A

degree to which the details and contours of objects can be perceived

It is defined in terms of the shortest distance by which two lines can be separated and still perceived as two lines

The normal eye sees two point sources of light as separate if they lie more than 2 microns apart on the fovea

Outside the fovea the visual acuity becomes progressively poorer decreasing to tenfold as the retinal periphery is reached

SNELLEN CHART

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3
Q

Average diameter of cones in the fovea

A

1.5 microns

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4
Q

How far apart must the centres of 2 spots of light be to be distinguished separately

A

Since the spot of light has a bright centre point and shaded edges a person can distinguish two separate points if their centres are approximately 2 microns apart on the retina (which is slightly greater than the width of a foveal cone)

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5
Q

Maximal visual acuity =>

A

A person with maximum visual acuity looking at two bright pinpoint spots of light from a distance of 10 metres can just barely distinguish them as two separate entities when they are 1.5 to 2 millimetres apart

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6
Q
A
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7
Q

Diagram of visual acuity

A
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8
Q

how is visual acuity expressed

A

As a ratio between the distance at which the subject can see the letters and that at which a subject with normal vision can see the letters

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9
Q

when to move subject when measuring acuity

A

Acuities worse than 6/60 - move subject to 4m from the chart

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10
Q

What measurement must be taken when analysing visual acuity

A

Width of smallest letter visible from 6m (in mm)

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11
Q

Calculation for visual acuity

A
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12
Q

Optic disc/papilla

A

Region of retina corresponding to confluence of optic nerve fibres as they pass out of the eye

region contains no photoreceptors and hence creates a blind spot in the visual field

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13
Q

Calculation for blind spot

A
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14
Q

visual field

A

that portion of the environment seen through that eye by the peripheries of the retina

This field would be circular but for the geography of the face i.e. the nose and the eyebrows limit the field of vision for each eye

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15
Q

where does the optic disc lie

A

The optic nerve and optic disc are on the nasal side of the eye relative to the fovea (centre of vision)

However when the visual field from both eyes is summated a larger field of vision is attained

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16
Q

What information does direct ophthalmoscopy tell us

A

Consists of looking at the fundus of the eye with a suitable light

yields information about diseases within the eye (e.g. cataract or vitreous haemhorrhage), in the cardiovascular system (i.e. hypertensive retinopathy) and in the central nervous system (i.e. papilloedema as seen in increased intracranial pressure)

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17
Q

Structure of ophthalmoscope

A

The light is focused on a mirror set at the top of the instrument so that the beam is deflected through at a right angle

The observer looks through a small hole in the mirror and shines a light into the subject’s eye

The ophthalmoscope has 30 lenses varying in focal length

Lenses marked in green text are convex and positive and are used to correct for a hypermetropic subject or examiner

Lenses with text coloured red are concave and negative and are used to correct for myopic examiner or subject

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18
Q

Red reflex

A

sparkly orange red colour

caused by light reflecting off of the retina and is the same phenomenon that produces red eyes in flash photographs

sometimes the translucent structures that allow light to pass unimpeded from outside the eye to the retina become opacified and the red reflex is lost

=> cataracts (clouding of lens)

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19
Q

atherosclerosis - change in retina

A

change in appearance of arteries

copper wiring

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20
Q

hypertension - changes in retina

A

alterations in the arterial-venous crossing pattern

a-v nicking

(vessels more obvious in superior and inferior aspects of retina, with relative sparing of temporal and medial regions)

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21
Q

BVs around optic disc

A

Less branching of BVs

point at which the vessels enter the retina along with the head of the optic nerve. The edges of this round disc are sharp and well defined in the normal state. It should be a bit more yellow/orange when compared to the rest of the retina

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22
Q

Optic cup

A

distinct circular area from which the blood vessels actually emerge

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23
Q

Where is the disc located

A

disc is not located in the exact centre of the retina but rather towards its medial/nasal aspect

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24
Q

Macula

A

region located lateral to the optic disc

It looks somewhat darker than the rest of the retina and, as opposed to the disc, has no distinct borders

The macula provides the sharpest vision

normally two disc widths temporal of the optic disc; it looks like a small dull red patch

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25
Q
A
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26
Q

Pitch

A

Tone

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27
Q

Intensity

A

Loudness

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28
Q

Timbre

A

Quality

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29
Q

2 types of deafness

A

Sensorineural

Conduction deafness

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30
Q

Rinne test tests for

A

Conductive deafness

as the sound disappears (from tuning forks), place instrument on mastoid process

If the sound vibrations reappear while in contact with the mastoid process ⇒ conductive deafness

⇒ negative Rinne (bone conduction > air conduction)

If subject cannot hear the vibrations ⇒ positive Rinne (air conduction > bone conduction)

31
Q

negative Rinne

A

bone conduction > air conduction

32
Q

positive Rinne

A

Air conduction > bone conduction

33
Q

Rinne test depends on

A

The fact that more sound reaches the cochlea if it has passed through the magnifying mechanism of the normal middle ear than if it has passed straight through the bone to the cochlea without magnification

34
Q

Weber test detects

A

Unilateral deafness

Fork on forehead

Conductive deafness: sound is referred to deafer ear - cochlea on that side is not distracted by extraneous noises and so the sound appears louder on the diseased side

1 normal ear, 1 ear with nerve deafness: sound will be more intense in the normal ear than the deaf one

35
Q

Schwabach test

A

Detects nerve deafness

place fork on mastoid process

when subject stops hearing sound, place fork on examiner’s mastoid process

if the examiner can still hear the sound freq, subject has some degree of nerve deafness

36
Q

Audiometry results

A
37
Q

Deafness severity scale

A
38
Q

Auriscopic examination

A

examines ext. auditory meatus and tympanic membrane

Draw the auricle upwards, backwards and laterally to straighten the kink in the external ear canal (it is drawn downwards and backwards in infants)

Continue to insert the auriscope until you see the eardrum

The normal drum appears pearly-grey in colour with the handle of the malleus visible and lying almost vertically near the centre of the tympanic membrane

A cone of light, the light reflex, reflects from its lower end downwards and forwards

39
Q

view of tympanic membrane with acute infection

A

dusky, red with loss of light reflex and possible bulging of drum

40
Q

view of tympanic membrane with glue ear

A

Retraction causing abnormal prominence of malleus

41
Q

view of tympanic membrane with perforation

A

Pinhole large especially in upper drum

42
Q

What is a grommet

A

a tiny plastic tube that is implanted in the tympanic membrane to drain the middle ear to relieve glue ear and recurrent middle ear infections

43
Q

conjuctiva

A

sensitive indicator of ocular disease

44
Q

where do the lacrimal glands lie

A
45
Q

overview of structures of eye

A
46
Q

optic nerve is also

A

afferent limbs for pupillary light reflex and lens accomodation

47
Q

efferents for pupillary light reflex

A

go to muscles of eye via oculomotor nerve

48
Q

muscle that elevates eyelid

A
49
Q

bepharoptosis

A

drooping eyelid

ptosis

50
Q

muscles of the eye

A
51
Q

innervation of muscles of eye

A
52
Q

presbyopia

A

impaired near vision

common with ageing

age associated lens changes gradually decreases the ability to focus on nearby objects

53
Q

what does jaundice present with

A

yellowing of sclera

54
Q

Anisocoria

A

difference of at least 4mm

55
Q

myosis

A

abnormally small

56
Q

mydriasis

A

significantly dilated

57
Q

nystagmus

A

involuntary rhythmic oscillation of the eyes - seen in cerebellar and vestibular disorders

58
Q

scotoma

A

abnormal blind spot

may be from macular degeneration

59
Q

locations in brain involved in processing blind spots

A
60
Q

what do neurons in the early part of the visual system do

A

construct perceptual experience

61
Q

diopter of < 0

A

useful in myopic or nearsighted patients

retina lies closer than normal to ophthalmoscope

62
Q

diopter > 0

A

useful in hyperopic or farsighted patients

retina is farther than normal from opthalmoscope

63
Q

fundus

A

choroid

retina

macula

fovea

retinal vessels

optic disc

64
Q
A
65
Q

optic disc

A
66
Q

fovea

A

lateral

centra vision

macula lies around it

67
Q

parts of outer ear

A
68
Q

eustachian tube connects

A

middle ear to nasopharynx

69
Q

conductive phase

A

outer and middle ear

70
Q

sensorineural phase

A

inner ear and cochlear nerve

71
Q

unilateral neurosensory hearing loss

A

sound is localised to good ear

72
Q

unilateral conductive hearing loss

A

sound is localised to impaired ear

73
Q

tympanic membrane

A
74
Q

parts of tympanic membrane

A

CNS (36 decks)

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