Misc

Question 1

clinical trials - phase 0

Answer 1

subjects: humans
microdosing for safety

Question 2

clinical trials - phase 1

Answer 2

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

Question 3

clinical trials - phase 2

Answer 3

subjects: target patients
IIA dosing
IIb efficacy

Question 4

clinical trails - phase 3

Answer 4

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

Question 5

clinical trials - phase 4

Answer 5

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

Question 6

visual standards group 1 entitlement - VA

Answer 6

 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

Question 7

visual standards group 1 entitlement - binocular field

Answer 7

 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

Question 8

visual standards group 1 entitlement - diplopia

Answer 8

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

Question 9

when to inform DVLA

Answer 9

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

Question 10

visual standards group 2 entitlement

Answer 10

 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

Question 11

blind registration

Answer 11

 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

Question 12

pelli-robson test purpose

Answer 12

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

Question 13

pelli-robson test procedure

Answer 13

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.

Question 14

pelli-robson test scoring

Answer 14

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.

Question 15

pelli-robson test interpretation

Answer 15

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

Question 16

photostress recovery testing

Answer 16

• 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

Question 17

photostress recovery testing abnormal time

Answer 17

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

Question 18

photostress recovery testing method

Answer 18

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

Question 19

photostress maculopathy results

Answer 19

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

Question 20

non-organic visual loss

Answer 20

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

Question 21

tests that do not rely on patients interpretation

Answer 21

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

Question 22

ishihara plates

Answer 22

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

Question 23

sensitivity for ishihara plates

Answer 23

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

Question 24

which axis does ishahra test

Answer 24

red-green axis

Question 25

what can test blue axis

Answer 25

Hardy-Rand-Rittler

Question 26

farnsworth munsell 100

Answer 26

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.

Question 27

relative insenitivty

Answer 27

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

Question 28

confocal microscopy

Answer 28

* 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

Question 29

uses of confocal microscopy

Answer 29

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

Question 30

specular microscopy

Answer 30

* Can provide objective measurements of corneal endothelial cells

Question 31

parameters of specular microscopy

Answer 31

o Density o Coefficient of variation o Percentage of hexagonal cells

Question 32

normal endothelial count in adults

Answer 32

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

Question 33

normal endothelial count in children

Answer 33

3500 cells/mm2 in children

Question 34

endothelial count <1000/m2

Answer 34

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

Question 35

coefficient varaition in specular mircosopcy

Answer 35

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)

Question 36

hess chart

Answer 36

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

Question 37

principles of hess chart

Answer 37

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

Question 38

hess chart set up

Answer 38

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.

Question 39

distance during hess chart examination

Answer 39

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

Question 40

interpreting a hess chart results

Answer 40

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

Question 41

nasolacrimal synringing

Answer 41

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

Question 42

results in canalicular obstruction

Answer 42

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.

Question 43

casts from nasolacrimal synringing

Answer 43

* Recovery of fluid in the nose after irrigation may be helpful in looking for casts or other debris.

Question 44

Synotophore

Answer 44

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).

Question 45

to detect arc

Answer 45

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

Question 46

results in normal retinal correspondance (NRC

Answer 46

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

Question 47

unharmonious ARC

Answer 47

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

Question 48

harmonious ARC

Answer 48

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

Question 49

definitive TB testing for occular uveitis

Answer 49

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

Question 50

Presumptive positive for TB

Answer 50

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

Question 51

limitations of TB skin test

Answer 51

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

Question 52

IGRA

Answer 52

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

Question 53

Investigations of myasthenia gravis

Answer 53

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

Question 54

ice pack test for MG

Answer 54

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

Question 55

antibody testing for MG

Answer 55

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