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Investigations > Misc > Flashcards

Misc Flashcards

1
Q

clinical trials - phase 0

A

subjects: humans
microdosing for safety

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2
Q

clinical trials - phase 1

A

subjects: healthy volunteers
safety, s/e, pharmacokinets and dynamics

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3
Q

clinical trials - phase 2

A

subjects: target patients
IIA dosing
IIb efficacy

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4
Q

clinical trails - phase 3

A

subjects: larger groups of paitents
Effectivenss vs gold standard (RCTS)

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5
Q

clinical trials - phase 4

A

subjects: target group
post-marketing survelliance and yellow card scheme

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6
Q

visual standards group 1 entitlement - VA

A

 Best corrected VA in good lighting sufficient to read a vehicle registration plate at
20 metres (where the figures are 5cm wide)
 The equivalent of this is approximately 6/9 and 6/12 Snellen VA

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7
Q

visual standards group 1 entitlement - binocular field

A

 There should be no major binocular field defect: no more than 3 contiguous points
missed in
 At least 120 degrees on the horizontal scale
 And within 20 degrees above and below fixation in the vertical
 The Esterman protocol is commonly used for binocular testing: uses a target
equivalent to the white Goldmann III4e setting

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8
Q

visual standards group 1 entitlement - diplopia

A

 New diplopia is a contraindication
 Diplopia must be controlled and the patient must have adapted

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9
Q

when to inform DVLA

A

 The DVLA should be informed about significant visual loss in one eye even if the
other meets the standard for driving

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10
Q

visual standards group 2 entitlement

A

 Best corrected VA at least 6/9 in the stronger eye
 Best corrected VA no worse than 6/12 in the other eye
 Uncorrected visual acuity must be at least 3/60 in both eyes
 NB: one eye with VA less than 3/60 is a contraindication to driving lorries,
buses
 Normal binocular field of vision
 New onset diplopia is a contraindication
 Diplopia must be controlled with prisms only (not with patching) and the
patient must have adapted

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11
Q

blind registration

A

 Best corrected visual acuity is less than 3/60; or,
 Best corrected visual acuity is between 6/60 and 3/60 with field constriction; or,
 Best corrected visual acuity is between 6/18 and 6/60 with severe field constriction

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12
Q

pelli-robson test purpose

A

Measures contrast sensitivity
o Method: Uses a single, large letter size (20/60 optotype).
o Contrast Variation: Across different groups of letters.

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13
Q

pelli-robson test procedure

A

o Starting Point: Patients read letters starting from the highest contrast.
o Continue until unable to correctly read 2 or 3 letters in a group.

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14
Q

pelli-robson test scoring

A

o Basis: Based on the contrast of the last group where 2 or 3 letters were correctly read.
o Logarithmic Measure: The score represents the subject’s contrast sensitivity.
o Example: A score of 2 indicates the ability to read at least 2 out of 3 letters at a contrast level of 1%(100% contrast sensitivity or log10 2), signifying normal contrast sensitivity.

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15
Q

pelli-robson test interpretation

A

o Less than 1.5: Consistent with visual impairment.
o Less than 1.0: Represents visual disability.

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16
Q

photostress recovery testing

A
  • Differentiate between vision loss caused by macular lesion/ ocular ischaemia versus optic neuropathy
  • Patient with optic neuropathy have normal photostress recovery time
  • The theory behind this is that resythesis of visual pigments is required by
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17
Q

photostress recovery testing abnormal time

A

o age macular degeneration
o central serous retinopathy
o diabetic retinopathy
o digitalis toxicity

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18
Q

photostress recovery testing method

A

o test the eye monocularly
o patient gazes into bright light 2-3 cm from the eye for 10 seconds
o as soon as light is removed, patient attempts to read the larger Snellen visual acuity line above the line representing the patient’s visual acuity prior to the bright light
o normal photostress recovery time is approximately 30 seconds or more

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19
Q

photostress maculopathy results

A

severe ocular ischaemia can have recovery times of 90-180 seconds

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20
Q

non-organic visual loss

A

o Spiraling, Crossing, Stacking of Isoptres on Goldmann Visual Field
o Clover leaf visual field defect on HVF 24-2

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21
Q

tests that do not rely on patients interpretation

A

o Swinging light test
o Optokinetic nystagmus drum response  used to elicit optokinetic nystagmus ( smooth pursuit with refixation saccade)
* Mirror test: when distracting a patient by holding conversation, move a mirror across their field of vision. It is difficult for patient to avoid looking at their own reflection

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22
Q

ishihara plates

A

screening test for red-green colour deficiency.
o Protan: red
o Deutan: Greeen

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23
Q

sensitivity for ishihara plates

A

o 95.5% on eight errors
o 97.5% on six errors
o 99% on three errors

24
Q

which axis does ishahra test

A

red-green axis

25
Q

what can test blue axis

A

Hardy-Rand-Rittler

26
Q

farnsworth munsell 100

A

very sensitive as the different in hues between adjacent tablets is divided across a spectrum of subtle shades
* Disadvantages: time consuming, difficult to complete for patient
* Quicker version of Farnsworth-Munsell is the Farnsworth Panel D-15, patients asked to arrange the tablets in sequence according to shades.

27
Q

relative insenitivty

A

People with mild degrees of colour deficiency might still be able to function in society practically. Eg: Fail Ishihara plates but pass D-15 can still function practically

28
Q

confocal microscopy

A
  • Non-invasive technique for in vivo imaging
  • Principle of confocal-single point of tissue illuminated by a point source of light; while simultaneously imaged by a camera in the same plane
  • Able to produce extremely thin images of the cornea serially and visualise the 5 layers of the cornea
29
Q

uses of confocal microscopy

A

o Identify organisms causing infectious keratitis such as Acanthamoeba, fungus, microspores, herpetic eye disease
o Evaluate cornea nerve morphology
o Evaluate cornea endothelial layer
o Differentiate corneal dystrophy

30
Q

specular microscopy

A
  • Can provide objective measurements of corneal endothelial cells
31
Q

parameters of specular microscopy

A

o Density
o Coefficient of variation
o Percentage of hexagonal cells

32
Q

normal endothelial count in adults

A

2000/mm2 in adults.
o Average is 2400 to 2500/ mm2.

33
Q

normal endothelial count in children

A

3500 cells/mm2 in children

34
Q

endothelial count <1000/m2

A

If density < 1000/mm2, the cornea might still be clear.
o However there is a high risk of decompensation following surgery such as phacoemulsification

35
Q

coefficient varaition in specular mircosopcy

A

Unitless number , usually less than 0.30. If > 0.40-can signify increase in variation ( also known as polymegethism which can occur in contact lens wearers)

36
Q

hess chart

A

investigations of incomitant strabismus ( angle of deviation of squinting eye not the same in all direction).

37
Q

principles of hess chart

A

o dissociation through a mirror/ or different coloured image
o foveal projection with normal retinal correspondence ( fovea-to fovea test)
o Hering and Sherrington law of innervation

38
Q

hess chart set up

A

angent patterns projected on a black/ grey background
o For dissociations through different coloured images, the fixing target is red and the projected light is green.
o The fixing eye will thus be given a red filter, and the fellow eye will be given a green filter. Alternatively, a mirror can be used to dissociate both eyes instead of the filter method.

39
Q

distance during hess chart examination

A

50cm away from the screen to avoid accommodation and convergence.
o Each small square subtends to 5 degrees at 50cm working distance.

40
Q

interpreting a hess chart results

A

o Which is the abnormal eye? The chart with the overall smaller field is the abnormal one
o Is it paralytic or restrictive? In restrictive/ mechanical defects, the affected eye shows an overall compressed field with limited muscle sequelae
o Is there a deviation in primary position? If the eye hyper/hypotropic or eso/exotropic?
o Which is the underacting muscle? It is easier to see this on the larger field as this represents greater movement the eye. Negative or inward displacement represents underaction
o Which is the overacting muscle? Positive or outward displacement represents overaction

41
Q

nasolacrimal synringing

A

non-physiologic evaluation of nasolacrimal system patency. Therefore, it gives no information on the adequacy of nasolacrimal drainage function under physiological conditions.

42
Q

results in canalicular obstruction

A

irrigation would be expected to regurgitate from the punctum being tested.
Reflux from the opposite punctum indicates obstruction at the level of the sac or duct.

43
Q

casts from nasolacrimal synringing

A
  • Recovery of fluid in the nose after irrigation may be helpful in looking for casts or other debris.
44
Q

Synotophore

A

measure all aspects of binocular single vision including simultaneous perception, fusion (including range of fusion) and stereopsis.
* It can also measure the degree of misalignment for horizontal, vertical and torsional misalignments in all directions of gaze.
* It can detect suppression and abnormal retinal correspondence (ARC).

45
Q

to detect arc

A

the synoptophore, the objective angle (OA) and subjective angle (SA) are measured, which gives the angle of anomaly (AOA).
o AOA = OA - SAr

46
Q

results in normal retinal correspondance (NRC

A

the SA is equal to OA and the AOA will be zero.

47
Q

unharmonious ARC

A

, the SA will be less than the OA (but the SA will not be zero)

48
Q

harmonious ARC

A

the SA will be zero, so the AOA will be equal to the OA.

49
Q

definitive TB testing for occular uveitis

A

o Acid fast smears of mycobacterial culture
o PCR based assays of ocular fluids
* This is usually challenging, with low sensitivity

50
Q

Presumptive positive for TB

A

o Positive TB skin test (TST)
o Positive interferon gamma release assay ( IGRA)
o Lesions of imaging of the chest
o Resolution / non-recurrence of uveitis following TB treatment

51
Q

limitations of TB skin test

A

o Lack of standardization for test administration and reading
o High false positive rates in patients immunized with BCG vaccine / exposed to nontuberculous mycobacteria
o False negative in severe illness and immunodeficiency

52
Q

IGRA

A

o Mechanism: measure interferon gamma response from sensitized T cells produce against Mycobacterium tuberculosis (ESAT 6, CFP 10, TB7.7)
o The proteins above not present in BCG vaccine, won’t get false positive in patient previously given BCG vaccine

53
Q

Investigations of myasthenia gravis

A

o Single fibre EMG: Jitters
o Repetitive nerve stimulation test: High specificity (95%)
o Antibody to acetylcholine receptor
o Ice pack test
o CT chest: Thymomas
o Anti-striated muscle antibody
o Tensilon Test

54
Q

ice pack test for MG

A

o Ice pack placed on ptotic eyelid/ affected muscle
o 75% sensitivity, but specific for MG
o Cold inhibits action of acetylcholinesterase

55
Q

antibody testing for MG

A

Acetylcholine receptor (AChR) antibodies
 Present in 90% of systemic MG
 50-70% of ocular MG

MuSK protein antibodies positive in 50% of those with -ve AChR antibodies
 If positive, less likely to have ocular features, thymoma

Striational antibodies
 Found more often in thymoma
 Marker for more severe MG

Investigations (8 decks)

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