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Green Book > Paper 3 > Flashcards

Paper 3 Flashcards

1
Q

From which embryological layer does the trabecular meshwork originate

A

Neural crest mesenchyme

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2
Q

How does Vancomycin work

A

Inhibitor of bacterial cell wall synthesis

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3
Q

What are features of polarised light

A

light waves which are all orientated in the same plane.
results in light of reduced intensity but spectral composition is unaffected.

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4
Q

How can polarisation be achieved

A

selective absorption (e.g. in dichroism),
reflection,
scattering
the use of birefringent materials

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5
Q

What does a dichroic substance do to light

A

only allows the transmission of light in an incident plane aligned with its structure by absorbing light waves in other planes.

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6
Q

Examples of dichroic substances

A

There are naturally occurring crystalline dichroic substances and, of the manufactured ones, the best known is polaroid

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7
Q

What is Polaroid dichroic substance composed of

A

iodoquinine crystals embedded in plastic.

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8
Q

What happens in Phase 0 of a clinical trial

A

Human microdosing studies to establish safety.

Healthy volunteers or target group of patients; usually <20 subjects

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9
Q

What happens in Phase 1 of a clinical trial

A

Assess principally safety and side effects, but also tolerability, pharmacokinetics and pharmacodynamics

Healthy volunteers or target group of patients; usually <100

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10
Q

What happens in Phase 2 of a clinical trial

A

Phase IIA: establish dosing
Phase IIB: establish efficacy

Target group of patients; usually <300

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11
Q

What happens in Phase 3 of a clinical trial

A

Determine effectiveness, in particular effectiveness vs current gold standard; usually randomised clinical trials

Target group of patients; typically 1000–3000

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12
Q

What happens in Phase 4 of a clinical trial

A

Postmarketing surveillance to detect side effects; further studies continue to assess effectiveness (e.g. in different populations)

Target group; thousands of patients

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13
Q

What does the grey line correspond to histologically

A

a superficial portion of the pretarsal orbicularis oculi (known as the muscle of Riolan) which marks the anterior border of the tarsal plate.

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14
Q

Type of collagen in the sclera

A

Type 1

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15
Q

Difference between the scleral and corneal stromal arrangement of collagen fibres

A

In the cornea, laminar construction is highly regular, as opposed to the sclera which has an irregular arrangement of collagen and elastic fibres.

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16
Q

Corneal endothelial cell density in an adult

A

2500 cells/mm squared

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17
Q

How many layers is the choroid made up of

A

4
From outside to inside
Haller Layer
Sattler Layer
Choriocapillaris
Bruch membrane (has 5 layers of its own)

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18
Q

What volume of the eye does the vitreous compose

A

2/3rd of the total volume

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19
Q

Does the posterior fontanelle close before anterior fontanelle

A

Yes

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20
Q

What does the coronal suture join

A

joins the frontal and parietal bones

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21
Q

What does the lambdoid suture join

A

posterior suture joining the occipital and parietal bones

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22
Q

What is the Geneva lens calibrated for

A

Crown glass refractive index

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23
Q

Where is the midstromal corneal plexus densest

A

In the peripheral cornea.

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24
Q

How many corneal stromal nerve fibres enter it

A

50–90 main stromal nerve fibres enter the cornea at the limbus in a radial direction.

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25
Q

How does ciliary muscle contraction lead to increased aqueous outflow

A

causes expansion of the three-dimensional structure of the trabecular meshwork which results in enlargement of the intertrabecular spaces and therefore reduction of the resistance to aqueous outflow.

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26
Q

What are the layers of the conjunctiva

A

Conjunctival epithelium
Conjunctival epithelial basement membrane
Conjunctival stroma

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27
Q

Which part of the conjunctival epithelium is stratified squamous non keratinized

A

Palpebral
Limbal

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28
Q

Which part of the conjunctival epithelium is stratified columnar

A

Bulbar

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29
Q

What connective tissue is the conjunctival stromal layer composed of

A

Loose connective tissue:
Superficial lymphoid layer
Deep collagenous fibrous layer attached to Tenon’s/episclera (apart from palpebral conjunctiva, where it adheres to posterior lamella)

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30
Q

Where does Toxoplasma gondi reproduce

A

in the intestinal mucosa of the cat, which is the definitive host, and the cysts pass into cat faeces.

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31
Q

How many axons compose the optic nerve

A

approximately 1.2 million axons, which arise from the retinal ganglion cells and synapse in the lateral geniculate body

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32
Q

How many layers are present in the primary visual cortex

A

6

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33
Q

What do layers 2 and 3 of the primary visual cortex do

A

Project to secondary visual cortex

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34
Q

What do layers 4 of the primary visual cortex do

A

Receives optic radiations from the lateral geniculate nucleus

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35
Q

What do layers 4 and 5 of the primary visual cortex do

A

Projects to the superior colliculus

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36
Q

What do layers 6 of the primary visual cortex do

A

Projects to lateral geniculate nucleus

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37
Q

What biochemical changes occur in the lens with cataract formation

A
  • Cross-linking (particularly disulphide bonds) and aggregation of lens proteins;
  • Increased susceptibility to oxidative damage, including a reduction in
    glutathione levels;
  • Loss of αA crystallin and γS crystallin.
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38
Q

How to calculate the degree of magnification with a direct ophthalmoscope

A

Mag=F/4. Total refracting power of the eye is approximately 60 dioptres. If myopic, add dioptric power, if hypermetropic subtract refracting power from 60. Then you divide by 4

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39
Q

what epithelium is found at the anterior lens capsule

A

Simple cuboidal epithelium

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40
Q

How is the uptake of glucose in the retina regulated

A

by the extracellular concentration of glucose rather than by insulin. Photoreceptors have a retina-specific insulin receptor that has a steady state of activity independent of hyper- or hypo- glycaemic states

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41
Q

How is the blood aqueous barrier maintained

A
  • Tight junctions between non-pigmented ciliary epithelial cells
  • Iris capillaries, which are non-fenestrated and essentially have tight junctions
    between vascular endothelial cells

NOTE: Desmosomes are found between the internal surfaces of the non-pigmented ciliary epithelial cells and do not form part of the blood– aqueous barrier.

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42
Q

What amino acid is melanin made from

A

Tyrosine which is synthesised from phenylalanine

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43
Q

Vtiligo vs albinism melanocytes

A

vitiligo lesions, melanocytes are absent
albinism, they are present but melanin production is impaired

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44
Q

Which enyzme impairment leads to vtiligo and albinism

A

Deficiency of the tyrosinase enzyme

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45
Q

What is the rate of production of CSF per day

A

550ml/day

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46
Q

What is the total volume of CSF

A

125–150 mL

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47
Q

Where is CSF produced and resorbed

A

Production is from the choroid plexus and the ventricle walls, and reabsorbtion is principally via the arachnoid villi with a small contribution from the cerebral venules.

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48
Q

Which bones of the orbit are formed from cartilagenous precursors

A

the lesser wing and the medial section of the greater wing of the sphenoid ossify in this way
Parts of the ethmoid bone also ossify from cartilage

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49
Q

Which bones of the orbit are derived from membranous ossification

A

All bones except lesser wing and medial section of sphenoid greater wing, ethmoid bone

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50
Q

What is the primary fixation reflex and is it present at birth

A

The primary fixation reflex, whereby the foveal fixation occurs with either eye, is present at birth.

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51
Q

When does the fovea develop

A

develops in the first few months of life, with increased cone density and myelination of the nerve fibres in the visual pathway.

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52
Q

When do smooth pursuit and accommodation develop

A

develop from 2 months.

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53
Q

When does convergence develop in the newborn

A

develops by 6 months.

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54
Q

What is the conjugate fixation reflex

A

The ability to move the eyes together during versions.
develops from 2 to 3 weeks of age

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55
Q

When does the ability to fix and follow a target develop from

A

6-8 weeks of age

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56
Q

Which gene mutation does Sturge Weber syndrome occur in

A

GNAQ gene

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57
Q

Which chromosome does NF-1 mutation occur in

A

17q (NF-1 gene)

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58
Q

Which chromosome does Tuberous sclerosis mutation occur in

A

9q and 16p (TSC1 and TSC2 gene)

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59
Q

Which chromosome does Von Hippel–Lindau syndrome occur in

A

3p (VHL gene)

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60
Q

Which phase is DNA synthesised in

A

S phase

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61
Q

What happens in the G1 phase of DNA synthesis

A

cell increases in size and synthesises required mRNA and proteins

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62
Q

What happens in the G2 phase of DNA synthesis

A

cell synthesises further proteins and grows in preparation for mitosis

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63
Q

Normal commensal flora of conjunctiva and eyelids

A

coagulase-negative staphylococci, such as Staphylococcus epidermidis.
Staphylococcus aureus, Micrococcus, and Corynebacteria, and anaerobes, such as Propionibacteria, which is found in meibomian glands.

Gram-negative organisms are also identified as commensals, albeit less frequently. These include Moraxella, Eschericia and Proteus species.

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64
Q

Which chromosome is the retinoblastoma gene mutation found on

A

Rb gene- Chromosome 13

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65
Q

Which chromosome is the Marfan’s syndrome gene mutation found on

A

fibrillin-1 (FNB1 gene) mutations on chromosome 15

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66
Q

Which chromosome is the Aniridia gene mutation found on

A

PAX6 mutation on Chromosome 11

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67
Q

Which chromosome is the Retinitis Pigmentosa gene mutation found on

A

RP2 and RPGR genes associated with X-linked RP
RHO (rhodopsin) gene on chromosome 3 (autosomal dominant RP)

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68
Q

Which adhesions are found between RPE cells

A

The blood–retinal barrier is sustained by tight junctions between endothelial cells of retinal vessels and between RPE cells

69
Q

Are there any tight junctions between RPE and choriocapillaris

A

NO

70
Q

Which immune cells release IL-2

A

T cells
IL-2 is thus the principal cytokine involved in T cell clonal proliferation.

71
Q

Which HLA are examples of MHC type 1

A

HLA A,B,C

72
Q

Which HLA are examples of MHC type 2

A

HLA D eg HLA DR4

73
Q

What type of image is formed by Purkinje 1,2,3 images

A

Erect virtual images

74
Q

What type of image is formed by Purkinje 4 image

A

Inverted, real image

75
Q

What does the Pelli Robson chart test

A

Contrast sensitivity

76
Q

What does the Farnsworth–Munsell 100 test

A

Hue testing

77
Q

What does the Hardy–Rand–Rittler test

A

protan deficit
deutan deficits
tritan deficit

78
Q

What does the Ishihara test

A

protan and deutan deficits

79
Q

Which conditions is HLA B27 positive associated with

A
  • Uveitis (commonly recurrent, unilateral anterior uveitis)
  • Seronegative spondarthritides, e.g. ankylosing spondylitis, psoriatic arthropathy,
    reactive arthritis
  • Inflammatory bowel disease
80
Q

What is the UK population prevalence of HLA B27 positive

A

8%

81
Q

What stain is used to test for Mycobacterium Tuberculosis

A

Lowenstein Jensen
Ziehl Neelsen

82
Q

What are endotoxins made from

A

lipopolysaccharides and are constituents of the outer membrane of the cell wall of Gram-negative bacteria.

83
Q

What are the glands of Zeis secreting

A

sebaceous glands which open into each lash follicle

84
Q

What are the glands of Moll secreting

A

modified sweat glands

85
Q

Which layers of the retina is drusen found in

A

deposits of extracellular debris between Bruch’s membrane and the RPE

86
Q

where does the levator muscle end in the tarsal plate

A

inserts into the anterior surface of the superior tarsal plate, with some fibres said to attach to the skin forming the upper lid skin crease

87
Q

Where does the muller muscle insert on the tarsal muscle

A

inserts into the superior border of the tarsus.

88
Q

How does Amphotericin work

A

It binds erogsterol in fungal cell membranes and increases membrane permeability as well as inducing oxidative damage.

89
Q

Why is amphotericin effective against yeast but not bacteria

A

It is very effective against yeasts, but not bacteria as their cell membranes do not contain ergosterol.

90
Q

What are some side effects of Amphotericin

A

usually given intravenously or topically. It is nephrotoxic, and its large side effect profile includes fever and hypokalaemia.

91
Q

What is a frame shift mutation

A

Insertions or deletions of nucleotides in groups not divisible by 3

92
Q

What are missense mutations

A

occur when a point mutation changes a codon from one amino acid to another

93
Q

What are nonsense mutations

A

point mutations that create a premature stop codon, and therefore an incomplete and often non-functional protein product

94
Q

What are silent mutations

A

have no phenotypical consequences and are generally either mutations in non- coding regions

95
Q

What zones does the iris collarette separate the iris into

A

collarette lies 2 mm from the pupil margin and separates the iris into a pupillary and a ciliary zone

96
Q

Is the collarette the thickest or thinnest part of the iris

A

Thickest

97
Q

is the dilator pupillae radial or concentric

A

radial arrangement

98
Q

is the constrictor pupillae radial or concentric

A

concentric in the pupillary zone

99
Q

What are connexins

A

a family of transmembrane proteins that are the constituent parts of connexons, which are hemichannels between the cytoplasm of two cells.

100
Q

Where are connexins found

A

Found at gap junctions and each cell will provide a connexon so that a complete channel is formed.

101
Q

Features of rigid contact lenses

A

have a fixed base curve and therefore a ‘tear lens’ usually forms between the lens and the cornea

102
Q

What does the shape of the tear lens interface depend on when wearing rigid contact lenses

A

depend on the difference between the base curve of the contact lens and the K readings of the cornea.

103
Q

What happens if the base curve of the contact lens and K reading are the same

A

a plano tear lens will be formed

104
Q

What happens if the K reading is greater than the base curve of the contact lens

A

a convex tear lens will be formed

105
Q

What happens if the K reading is less than the base curve of the contact lens

A

a concave tear lens will be formed.

106
Q

What deviation does a Dove prism do to the image

A

used to invert an image, but cause no deviation or lateral transposition.

107
Q

Which gene and chromosome is affected in Gorlin Goltz syndrome

A

autosomal dominant pattern of inheritance
mutations in the PTCH1 gene on chromosome 9, which produces the protein patched 1

108
Q

What is Patched 1 protein responsible for and which condition is it affected in

A

Patched-1 interacts with sonic hedgehog during development, and acts to suppress cell growth and division.

109
Q

What kind of photo______ does NdYAG laser do

A

Photodisruption

110
Q

What kind of photo______ does Argon and cyclodiode lasers do

A

Photocoagulation

111
Q

What kind of photo______ does excimer laser do

A

Photoablation

112
Q

What is Whitnall ligament

A

a condensation of fascial tissue running horizontally just below the superior orbital rim from the lacrimal gland to the trochlea.

The levator muscle alters direction at Whitnall’s ligament from horizontal to vertical, and thus the ligament acts as a fulcrum for the levator

113
Q

What is the % hydration of the cornea compared to sclera

A

Cornea: 80% hydrated.
Sclera: 70% hydrated

114
Q

What is the impact of mydriasis on depth and field of focus

A

Mydriasis causes a decrease in the depth of field and the depth of focus

115
Q

What is the impact of miosis on depth and field of focus

A

increases both the depth of field and depth of focus

116
Q

What is the impact of pupil size on spherical and chromatic aberration

A

Spherical aberration increases to the fourth power of pupil size and it is this that is responsible for the greatest part of the blurred vision associated with mydriasis.

117
Q

What is the Stiles Crawford effect

A

is the observation that photoreceptors respond less to light entering through the periphery of the lens than through the centre

118
Q

What are the 2 unpaired facial bones

A

The vomer and the mandible

119
Q

What is the normal horizontal visual field of the eye in degrees

A

extends 90–100° temporally and 60° nasally, giving a horizontal field of 150–160°

120
Q

What is the normal vertical visual field of the eye in degrees

A

it extends 70–80° inferiorly and 50–60° superiorly.

121
Q

Where is the blind spot located relative to fixation

A

An absolute scotoma 10-20 degrees temporal to fixation.

122
Q

Which telescope principle is useful for low vision aids

A

Gallilean. The objective and eyepiece lenses are separated by the difference between their focal lengths

123
Q

What is stage 1 of Trachoma

A

conjunctival hyperaemia, early lymphoid hyperplasia, and oedema of the conjunctival stroma with infiltrating polymorphs

124
Q

What is stage 2 of Trachoma

A

shows mature follicles and/or papillae, with peripheral corneal fibrovascular pannus formation

125
Q

What is stage 3 of trachoma

A

the inflammatory tissue is replaced by fibrous material

126
Q

What is stage 4 of trachoma

A

contraction of the palpebral conjunctival stroma, leading to entropion, trichiasis and corneal damage.

127
Q

What are Langhans type giant cells

A

multinucleate giant cells which are formed from the fusion of epithelioid macrophages within a granuloma

128
Q

What type of nuclei do Langhans type giant cells form

A

Horseshoe shape around the cell periphery

129
Q

Viruses causing acute retinal necrosis

A

commonly implicated pathogens are varicella zoster virus and herpes simplex viruses 1 and 2.
Less commonly cytomegalovirus and Epstein–Barr virus can be the cause.

130
Q

Does Acute retinal necrosis occur in immunocompetent individuals

A

Yes

131
Q

Does Progressive outer retinal necrosis occur in immunocompromised individuals

A

Yes

132
Q

Difference in presentation of ARN and PORN

A

both are believed to result from herpes virus infection, PORN does not have the associated vitritis, vasculitis or papillitis of ARN.

133
Q

Prismatic effect of lens formula by decentration

A

P=FXD
P is the prism power (in prism dioptres); F is the power of the lens (in dioptres); D is the decentration (in cm)

134
Q

Is VZV DNA/RNA virus

A

Double stranded DNA virus

135
Q

How does Aciclovir work

A

inhibition of viral DNA synthesis.

136
Q

How do Quinolones work

A

interact with bacterial DNA gyrase and topoisomerase IV, enzymes essential for bacterial DNA replication.

137
Q

What is metastatic calcification

A

when it occurs in normal tissues, classically in the presence of hypercalcaemia. For example, in chronic renal failure, secondary hyperparathyroidism can lead to hypercalcaemia and metastatic calcification;

138
Q

What is dystrophic calcifcation

A

occurs in normocalcaemia, typically in necrotic or hyalinised tissue. An example of this is a phthisical eye.

139
Q

Which corneal layers does Band Keratopathy occur in

A

non-specific and involves calcification of the superficial stroma and Bowman’s layer in the interpalpebral cornea

140
Q

What are the predominant cells found in acute inflammation

A

Neutrophils

141
Q

What are the predominant cells found in chronic inflammation

A

predominantly macrophages and lymphocytes.

142
Q

What is Bergemeister papillae

A

cone-like fibrous structure that is sometimes observed at the optic nerve head as a remnant of the hyaloid artery.

143
Q

What is Mittendorf’s dot

A

a small opacity that is sometimes observed on the posterior lens capsule at the point of anterior attachment of the hyaloid artery

144
Q

What is a Forster-Fuch’s spot

A

a pigmented macular scar associated with pathological myopia.

145
Q

How long can steroids take to have effect

A

Causes changes in gene transcription, they can take hours or days to develop.
An important component of this is reducing the transcription of the gene for cyclooxygenase-2, which results in decreased prostanoid production.

146
Q

Which anaesthetic agents cause a rise in IOP

A

Suxamethonium
Ketamine

147
Q

Which anaesthetic agents cause a fall in IOP

A

Inhalational anaesthetic agents
all intravenous induction agents except ketamine

148
Q

How long does the effect of Atropine last

A

upto 7 days

149
Q

How long does the effect of Homatropine last

A

6 hours to 4 days

150
Q

How long does the effect of Cyclopentolate last

A

up to 24 hours

151
Q

How long does the effect of Tropicamide last

A

4–6 hours

152
Q

What is the inheritance pattern of Tay Sachs disease

A

autosomal recessive condition

153
Q

What is the pathophysiology of Tay Sachs disease

A

progressive neurodegeneration caused by accumulation of GM2 ganglioside molecules.

154
Q

Which gene mutation and chromosome is responsible for Tay Sach’s disease

A

mutations of the HEXA gene on chromosome 15 which encodes a component of a lysosomal enzyme

155
Q

What causes the oxygen dissociation curve to shift to the right

A

(reduced oxygen binding affinity) by increasing acidity and pCO2 (the Bohr effect), temperature and 2,3-DPG.

156
Q

What is haemoglobin composed of

A
  • Haem, a derivative of porphyrin containing ferrous (Fe2+) iron (oxidation to ferric or Fe3+ iron occurs in methaemoglobinaemia)
  • Globin, which consists of four polypeptide chains (each with a haem moeity)
157
Q

What is the ratio of photoreceptor cells to RPE cells at the posterior pole

A

45:1 at the posterior pole.

158
Q

What is the rate of production of aqueous humour

A

approximately 2.5 μL/min

159
Q

What are the properties of the image formed by a prism

A

Virtual
Erect
Displaced towards the apex

160
Q

Which layers of the LGN do the contralateral fibres receive

A

1,4,6

161
Q

Which layers of the LGN do the ipsilateral nerve fibres receive

A

2,3,5

162
Q

Which nerve arises from the 1st pharyngeal arch

A

Trigeminal (V) – maxillary and mandibular branches

163
Q

Which nerve arises from the 2nd pharyngeal arch

A

Facial (VII)

164
Q

Which nerve arises from the 3rd pharyngeal arch

A

Glossopharyngeal (IX)

165
Q

Which nerve arises from the 4th pharyngeal arch

A

Vagus (X) – superior laryngeal branch

166
Q

Which nerve arises from the 6th pharyngeal arch

A

Vagus (X) – recurrent laryngeal branch

167
Q

Disadvantages of viral vectors

A
  • They can only carry a limited amount of genetic material, so some genes are too large
  • They are immunogenic.
168
Q

What is the standard error of the mean

A

a measure of how good an estimate the mean of a sample from a population is of the true mean of that population. It is calculated using the following formula:
SEM = S √n

S is the standard deviation of the sample
n is the sample size (in this case 100).

169
Q

What structures pass through Foramen ovale

A

O – Otic ganglion
V – V3 (mandibular branch of the trigeminal nerve)
A – Accessory meningeal artery
L – Lesser petrosal nerve (this may also pass via other small foraminae between
the foramen ovale and foramen spinosum) E – Emissary veins

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