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Blue Book > Paper 4 > Flashcards

Paper 4 Flashcards

1
Q

What is the main source of image imperfection when the pupil is small

A

Diffraction

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2
Q

What is the Stiles Crawford effect

A

refers to the directional sensitivity of the cone photoreceptors

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3
Q

What are the optics of the Frisby test

A

Frisby test consists of three clear plastic plates of different thicknesses. Each Frisby test plate features four squares, of which only one features a ‘hidden’ circle.

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4
Q

How many degrees is 1 prism dioptre

A

1/2 degree

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5
Q

In a colour blind patient how is the duochrome test done

A

asked whether the upper (red) or lower (green) rank of circles appears clearer (or letters, in older charts).

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6
Q

What is static refraction

A

The dioptric power of the resting eye

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7
Q

What is dynamic refraction

A

The dioptric power of the accommodated eye

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8
Q

What range of dioptric power does a pinhole correct

A

+4 to -4

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9
Q

How can an eye be rendered emmetropic post cataract surgery

A

If the degree of axial myopia is approximately −18 to −20 D

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10
Q

Why do rigid contact lenses cause a halo effect if the pupil is dilated

A

due to refraction of the peripheral lens or adjacent tear film.

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11
Q

In a standard loupe where is the object situated

A

between the first principal focus and the lens.

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12
Q

What magnification do bar shaped convex cylindrical lenses create

A

vertical magnification of the letters when placed on a line of printed text.

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13
Q

In indirect ophthalmoscopy how much magnification does the +13D lens create

A

approximately 5x magnification

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14
Q

In indirect ophthalmoscopy how much magnification does the +20D lens create

A

approximately x3 magnification

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15
Q

Is the peripheral cornea flatter than the central cornea

A

YES

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16
Q

What diameter of the central cornea is used for vision

A

4mm

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17
Q

What is the resulting image of a Galilean telescope

A

real, inverted, and magnified.

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18
Q

Which purkinje samson images are used to measure AC depth

A

Images 2 and 3

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19
Q

What wavelength of light does the Nd YAG laser emit

A

1064nm

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20
Q

How many meibomian glands are found on the upper lid

A

30

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21
Q

AP diameter of the eye

A

24mm

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22
Q

Vertical diameter of the eye

A

23mm

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23
Q

Horizontal diameter of the eye

A

23.5mm

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24
Q

Longest rectus muscle tendon length

A

Lateral Rectus 8.8mm

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25
Q

Shortest rectus muscle tendon length

A

Medial 3.7mm

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26
Q

What are the anterior and posterior boundaries of the anterior cranial fossa

A

Anterior->frontal bone
Posteriorly-> sharp lesser wing of sphenoid.

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27
Q

What volume does the vitreous occupy in the eyeball

A

4/5 (80%)

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28
Q

What are the 3 axes of Fick

A

Vertical abduction and adduction
Transverse elevation and depression
Sagittal extorsion and intorsion

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29
Q

Where is the CN4 nucleus located

A

in the midbrain at the level of the inferior colliculus

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30
Q

What percentage of optic nerve axons originate from midget ganglion cells

A

90%- associated with cones

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31
Q

What percentage of ganglion cells associated with rods from the peripheral retina

A

10%- associated with rods

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32
Q

Which EOM are visible at week 5

A

lateral rectus,
superior rectus,
levator palpebrae superioris

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33
Q

Which EOM are visible at week 6

A

superior oblique
medial rectus

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34
Q

Which EOM are visible after week 6

A

Inferior oblique
Inferior rectus

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35
Q

Order of lacrimal drainage structures

A

From eye to nose, are as follows:
superior and inferior puncta,
superior and inferior canaliculi,
common canaliculus,
nasolacrimal sac,
nasolacrimal duct,
plica lacrimalis.

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36
Q

How frequently do the cell layers of the corneal epithelium turn over

A

Every 7-10 days

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37
Q

What are the 2 remnants of the fetal hyaloid artery

A

Bergmeister’s papilla- at the optic disc
Mittendorf’s dot - posterior lens capsule

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38
Q

What is the percentage of oxygen saturation of the venous blood of the choroid

A

over 90%

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39
Q

What happens to lens nucleus thickness in accommodation

A

thickness of the nucleus increases but the thickness of the cortex does not change

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40
Q

What is the equivalence of 1 apostilb in lumen/m2

A

1lumen/m2

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41
Q

What is the equivalence of 1 lux

A

1 metre-candela

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42
Q

What is the equivalence of 1 lambert

A

1 candela at 1 cm distance for a perfectly diffusing light source on a surface at 1 cm.

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43
Q

How many muscle fibres per motor unit are present in the human body

A

80-100

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44
Q

What does the Frank Starling mechanism of the heart state

A

the more the cardiac muscle is stretched during filling, the greater the force of
contraction and the greater the volume of blood pumped into the aorta

45
Q

What is the dorsal respiratory group responsible for

A

Inspiration

46
Q

What is the ventral respiratory group responsible for

A

Expiration

47
Q

What does the pneumotaxic centre govern

A

rate and depth of breathing

48
Q

What does the smooth endoplasmic reticulum primarily secrete

A

site of synthesis of lipids, triglycerides, and steroids

49
Q

Which cells of the eye is the smooth endoplasmic reticulum primarily found

A

RPE
Meibomian gland cells

50
Q

What kind of cells is the rough endoplasmic reticulum found in

A

highly developed in secretory cells, including the lacrimal gland acinar cell.

51
Q

What wavelength light does the cornea absorb

A

Short wavelength light

52
Q

Where are hard and soft drusen located in the retina

A

between the retinal pigment epithelium (RPE) basement membrane and Bruch’s membrane

53
Q

Where are basal linear deposits located in the retina

A

between the RPE basement membrane and RPE cell cytoplasm.

54
Q

What is the commonest protozoal parasite to infect the eye

A

Toxoplasma gondii

55
Q

What are the classic tetrad of features of infection with Toxoplasma gondii

A

meningoencephalitis,
hydrocephalus,
intracranial
calcification,
retinochoroiditis

56
Q

Risk factors for primary angle closure glaucoma

A

advancing age,
female sex,
family history of primary angle-closure glaucoma,
hypermetropia,
shallow anterior chamber depth,
short axial length,
anteroposterior thickening of the lens.

57
Q

What is the pathophysiology of Cogan dystrophy

A

degeneration of cells with cyst formation, causing an unstable corneal epithelium.

58
Q

What are some features found in ARN but not PORN

A

retinal vasculitis,
papillitis.

THESE ARE NOT FOUND IN PORN

59
Q

What is endophytic growth in retinoblastoma

A

into the vitreous

60
Q

What is exophytic growth in retinoblastoma

A

into the subretinal space

61
Q

What are Homer Wright Rosettes

A

a multilayered circle of nuclei surrounding eosinophilic fibrillate material, with no lumen or internal limiting membrane.

62
Q

What are Fleurettes

A

primitive photoreceptor bodies, arranged in a ‘fleur de lys’ shape

63
Q

Which HHV virus causes Kaposi Sarcoma

A

HHV8

64
Q

Which Chlamydia serotypes cause urogenital infections

A

Serotypes D-K

65
Q

Which immune cells feature several mitochondria and ribosomes

A

Basophils

66
Q

By what percentage do beta blockers reduce IOP

A

50%

67
Q

What class of drug is apraclonidine

A

Parasympathetic agonist

68
Q

How does Tacrolimus work

A

inhibits interleukin-2.

69
Q

How does Mycophenolate work

A

blocks the de novo pathway of purine synthesis (selective for lymphocytes)

70
Q

What does Prostaglandin I2 cause

A

vasodilation and reduces platelet adhesion.

71
Q

What does Prostaglandin F2 alpha cause

A

bronchial smooth muscle contraction

72
Q

What does Prostaglandin E2 cause

A

vasodilation, bronchodilation, uterine contraction, fever, macrophage activation, and release of pituitary hormones, adrenal cortex steroids, and insulin from the pancreas

73
Q

What does Leukotriene B4 cause

A

aggregation of neutrophils, chemotaxis, and stimulation of phospholipase A2

74
Q

What does Leukotriene D4 cause

A

contraction of smooth muscle, vasoconstriction, and bronchoconstriction

75
Q

What does Thromboxane A2 cause

A

vasoconstriction, bronchoconstriction, and platelet aggregation

76
Q

What does the Hardy Weinburg equilibrium assert

A

genetic variation of a population remains constant from one generation to the next, in the absence of disturbing factors such as mutation and selection

77
Q

Which cells are affected in retinoblastoma

A

Primitive photoreceptor cells

78
Q

Does retinoblastoma have a preference for affecting males/females

A

NO- Males females equally affected

79
Q

What does Traquir analogy of the visual field demonstrate

A

the visual field is ‘an island of vision surrounded by a sea of darkness’.

80
Q

In Traquir analogy what is the hill of vision

A

the fovea represents the peak of the ‘hill’

81
Q

In Traquair analogy what does the ground level represent

A

the visual field extends 50° superiorly, 60° nasally, 70° inferiorly, and 90° temporally

82
Q

What is the pattern standard deviation

A

a measure of variability or focal loss within the visual field. PSD takes into account any generalised depression

83
Q

What is a high PSD indicative of

A

a high PSD is more indicative of glaucomatous field loss than mean deviation, which is simply a measure of overall field loss.

84
Q

What is the field of view of a fundus photograph

A

30-35 degrees

85
Q

In FFA what is a window defect most likely caused by

A

RPE defect conditions eg macula hole/RPE atrophy

86
Q

What cell layers of the retina are hyperreflective on OCT

A

the nerve fibre layer and inner and outer plexiform layers are typically hyperreflective

87
Q

What cell layers of the retina are hyporeflective on OCT

A

The ganglion cell layer and inner and outer nuclear layers

88
Q

What layers are lost in Geographic atrophy

A

an advanced form of dry AMD associated with atrophy of the outer retina, RPE, and choriocapillaris, leading to permanent loss in vision

89
Q

In ocular Ultrasonography what does the gain control do

A

adjust the amplification of the reflected signal. It does not change the amount
of ultrasonic energy emitted from the probe

90
Q

What are the features of choroidal melanoma on A-scan

A

typically show medium to low internal reflectivity.

91
Q

What are the features of choroidal melanoma on B scan

A

appear dome-shaped; other characteristics include an acoustically hollow zone within the melanoma, subretinal fluid, and choroidal excavation.

92
Q

What are the features of optic disc drusen on B scan

A

their high reflectivity

93
Q

What are the features of posterior scleritis on B scan

A

well-defined, thickened sclera and fluid in Tenon’s space

94
Q

What is the rod response ERG

A

obtained after dark adaptation (20 minutes in the dark) is achieved using a dim white flash below cone sensitivity— this comprises a b-wave only.

95
Q

What is the maximal ERG

A

obtained from dark adapted eyes using a bright white flash is a mixed rod and cone
response

96
Q

Which conditions reduce A and B waves on ERG

A

These can be remembered using the acronym, ‘ROD CRAM’

Rod-cone dystrophies (including retinitis pigmentosa),
Ophthalmic artery occlusion,
Drug toxicity (e.g. phenothiazines),
Cancer-associated retinopathy,
total Retinal detachment,
Autoimmune retinopathy,
Metallosis.

97
Q

What ERG response does X linked retinoschisis cause

A

cause a normal a-wave and reduced scotopic b-wave, also termed an ‘electronegative’ response

98
Q

How is the ARR calculated

A

control event rate minus experimental event rate

99
Q

What does the solid vertical line on a Forest plot represent

A

Line of no effect

100
Q

What does the size of the box on a Forest plot represent

A

individual study power (and therefore sample size)

101
Q

What does the horizontal whiskers on a Forest plot represent

A

indicate the confidence intervals per individual study

102
Q

WHO criteria for mild distance visual impairment

A

visual acuity worse than 6/12 to 6/18.

103
Q

WHO criteria for moderate distance visual impairment

A

visual acuity worse than 6/18 to 6/60.

104
Q

WHO criteria for severe distance visual impairment

A

visual acuity worse than 6/60 to 3/60

105
Q

WHO criteria for blindness

A

visual acuity worse than 3/60

106
Q

WHO criteria for near vision impairment

A

Near visual acuity worse than N6 or M.08 at 40 cm.

107
Q

What is attrition bias

A

due to unequal loss of participants from different arms of a trial

108
Q

What is selection bias

A

caused by failure to achieve proper randomisation during participant selection

109
Q

What is confirmation bias

A

caused by the tendency to search for or favour information that confirms prior beliefs

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