Paper 3 Flashcards
(169 cards)
1
Q
From which embryological layer does the trabecular meshwork originate
A
Neural crest mesenchyme
2
Q
How does Vancomycin work
A
Inhibitor of bacterial cell wall synthesis
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.
4
Q
How can polarisation be achieved
A
selective absorption (e.g. in dichroism),
reflection,
scattering
the use of birefringent materials
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.
6
Q
Examples of dichroic substances
A
There are naturally occurring crystalline dichroic substances and, of the manufactured ones, the best known is polaroid
7
Q
What is Polaroid dichroic substance composed of
A
iodoquinine crystals embedded in plastic.
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
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
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
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
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
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.
14
Q
Type of collagen in the sclera
A
Type 1
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.
16
Q
Corneal endothelial cell density in an adult
A
2500 cells/mm squared
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)
18
Q
What volume of the eye does the vitreous compose
A
2/3rd of the total volume
19
Q
Does the posterior fontanelle close before anterior fontanelle
A
Yes
20
Q
What does the coronal suture join
A
joins the frontal and parietal bones
21
Q
What does the lambdoid suture join
A
posterior suture joining the occipital and parietal bones
22
Q
What is the Geneva lens calibrated for
A
Crown glass refractive index
23
Q
Where is the midstromal corneal plexus densest
A
In the peripheral cornea.
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.
25
How does ciliary muscle contraction lead to increased aqueous outflow
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.
26
What are the layers of the conjunctiva
Conjunctival epithelium
Conjunctival epithelial basement membrane
Conjunctival stroma
27
Which part of the conjunctival epithelium is stratified squamous non keratinized
Palpebral
Limbal
28
Which part of the conjunctival epithelium is stratified columnar
Bulbar
29
What connective tissue is the conjunctival stromal layer composed of
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)
30
Where does Toxoplasma gondi reproduce
in the intestinal mucosa of the cat, which is the definitive host, and the cysts pass into cat faeces.
31
How many axons compose the optic nerve
approximately 1.2 million axons, which arise from the retinal ganglion cells and synapse in the lateral geniculate body
32
How many layers are present in the primary visual cortex
6
33
What do layers 2 and 3 of the primary visual cortex do
Project to secondary visual cortex
34
What do layers 4 of the primary visual cortex do
Receives optic radiations from the lateral geniculate nucleus
35
What do layers 4 and 5 of the primary visual cortex do
Projects to the superior colliculus
36
What do layers 6 of the primary visual cortex do
Projects to lateral geniculate nucleus
37
What biochemical changes occur in the lens with cataract formation
* 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.
38
How to calculate the degree of magnification with a direct ophthalmoscope
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
39
what epithelium is found at the anterior lens capsule
Simple cuboidal epithelium
40
How is the uptake of glucose in the retina regulated
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
41
How is the blood aqueous barrier maintained
* 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.
42
What amino acid is melanin made from
Tyrosine which is synthesised from phenylalanine
43
Vtiligo vs albinism melanocytes
vitiligo lesions, melanocytes are absent
albinism, they are present but melanin production is impaired
44
Which enyzme impairment leads to vtiligo and albinism
Deficiency of the tyrosinase enzyme
45
What is the rate of production of CSF per day
550ml/day
46
What is the total volume of CSF
125–150 mL
47
Where is CSF produced and resorbed
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.
48
Which bones of the orbit are formed from cartilagenous precursors
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
49
Which bones of the orbit are derived from membranous ossification
All bones except lesser wing and medial section of sphenoid greater wing, ethmoid bone
50
What is the primary fixation reflex and is it present at birth
The primary fixation reflex, whereby the foveal fixation occurs with either eye, is present at birth.
51
When does the fovea develop
develops in the first few months of life, with increased cone density and myelination of the nerve fibres in the visual pathway.
52
When do smooth pursuit and accommodation develop
develop from 2 months.
53
When does convergence develop in the newborn
develops by 6 months.
54
What is the conjugate fixation reflex
The ability to move the eyes together during versions.
develops from 2 to 3 weeks of age
55
When does the ability to fix and follow a target develop from
6-8 weeks of age
56
Which gene mutation does Sturge Weber syndrome occur in
GNAQ gene
57
Which chromosome does NF-1 mutation occur in
17q (NF-1 gene)
58
Which chromosome does Tuberous sclerosis mutation occur in
9q and 16p (TSC1 and TSC2 gene)
59
Which chromosome does Von Hippel–Lindau syndrome occur in
3p (VHL gene)
60
Which phase is DNA synthesised in
S phase
61
What happens in the G1 phase of DNA synthesis
cell increases in size and synthesises required mRNA and proteins
62
What happens in the G2 phase of DNA synthesis
cell synthesises further proteins and grows in preparation for mitosis
63
Normal commensal flora of conjunctiva and eyelids
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.
64
Which chromosome is the retinoblastoma gene mutation found on
Rb gene- Chromosome 13
65
Which chromosome is the Marfan's syndrome gene mutation found on
fibrillin-1 (FNB1 gene) mutations on chromosome 15
66
Which chromosome is the Aniridia gene mutation found on
PAX6 mutation on Chromosome 11
67
Which chromosome is the Retinitis Pigmentosa gene mutation found on
RP2 and RPGR genes associated with X-linked RP
RHO (rhodopsin) gene on chromosome 3 (autosomal dominant RP)
68
Which adhesions are found between RPE cells
The blood–retinal barrier is sustained by tight junctions between endothelial cells of retinal vessels and between RPE cells
69
Are there any tight junctions between RPE and choriocapillaris
NO
70
Which immune cells release IL-2
T cells
IL-2 is thus the principal cytokine involved in T cell clonal proliferation.
71
Which HLA are examples of MHC type 1
HLA A,B,C
72
Which HLA are examples of MHC type 2
HLA D eg HLA DR4
73
What type of image is formed by Purkinje 1,2,3 images
Erect virtual images
74
What type of image is formed by Purkinje 4 image
Inverted, real image
75
What does the Pelli Robson chart test
Contrast sensitivity
76
What does the Farnsworth–Munsell 100 test
Hue testing
77
What does the Hardy–Rand–Rittler test
protan deficit
deutan deficits
tritan deficit
78
What does the Ishihara test
protan and deutan deficits
79
Which conditions is HLA B27 positive associated with
* Uveitis (commonly recurrent, unilateral anterior uveitis)
* Seronegative spondarthritides, e.g. ankylosing spondylitis, psoriatic arthropathy,
reactive arthritis
* Inflammatory bowel disease
80
What is the UK population prevalence of HLA B27 positive
8%
81
What stain is used to test for Mycobacterium Tuberculosis
Lowenstein Jensen
Ziehl Neelsen
82
What are endotoxins made from
lipopolysaccharides and are constituents of the outer membrane of the cell wall of Gram-negative bacteria.
83
What are the glands of Zeis secreting
sebaceous glands which open into each lash follicle
84
What are the glands of Moll secreting
modified sweat glands
85
Which layers of the retina is drusen found in
deposits of extracellular debris between Bruch’s membrane and the RPE
86
where does the levator muscle end in the tarsal plate
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
Where does the muller muscle insert on the tarsal muscle
inserts into the superior border of the tarsus.
88
How does Amphotericin work
It binds erogsterol in fungal cell membranes and increases membrane permeability as well as inducing oxidative damage.
89
Why is amphotericin effective against yeast but not bacteria
It is very effective against yeasts, but not bacteria as their cell membranes do not contain ergosterol.
90
What are some side effects of Amphotericin
usually given intravenously or topically. It is nephrotoxic, and its large side effect profile includes fever and hypokalaemia.
91
What is a frame shift mutation
Insertions or deletions of nucleotides in groups not divisible by 3
92
What are missense mutations
occur when a point mutation changes a codon from one amino acid to another
93
What are nonsense mutations
point mutations that create a premature stop codon, and therefore an incomplete and often non-functional protein product
94
What are silent mutations
have no phenotypical consequences and are generally either mutations in non- coding regions
95
What zones does the iris collarette separate the iris into
collarette lies 2 mm from the pupil margin and separates the iris into a pupillary and a ciliary zone
96
Is the collarette the thickest or thinnest part of the iris
Thickest
97
is the dilator pupillae radial or concentric
radial arrangement
98
is the constrictor pupillae radial or concentric
concentric in the pupillary zone
99
What are connexins
a family of transmembrane proteins that are the constituent parts of connexons, which are hemichannels between the cytoplasm of two cells.
100
Where are connexins found
Found at gap junctions and each cell will provide a connexon so that a complete channel is formed.
101
Features of rigid contact lenses
have a fixed base curve and therefore a ‘tear lens’ usually forms between the lens and the cornea
102
What does the shape of the tear lens interface depend on when wearing rigid contact lenses
depend on the difference between the base curve of the contact lens and the K readings of the cornea.
103
What happens if the base curve of the contact lens and K reading are the same
a plano tear lens will be formed
104
What happens if the K reading is greater than the base curve of the contact lens
a convex tear lens will be formed
105
What happens if the K reading is less than the base curve of the contact lens
a concave tear lens will be formed.
106
What deviation does a Dove prism do to the image
used to invert an image, but cause no deviation or lateral transposition.
107
Which gene and chromosome is affected in Gorlin Goltz syndrome
autosomal dominant pattern of inheritance
mutations in the PTCH1 gene on chromosome 9, which produces the protein patched 1
108
What is Patched 1 protein responsible for and which condition is it affected in
Patched-1 interacts with sonic hedgehog during development, and acts to suppress cell growth and division.
109
What kind of photo______ does NdYAG laser do
Photodisruption
110
What kind of photo______ does Argon and cyclodiode lasers do
Photocoagulation
111
What kind of photo______ does excimer laser do
Photoablation
112
What is Whitnall ligament
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
What is the % hydration of the cornea compared to sclera
Cornea: 80% hydrated.
Sclera: 70% hydrated
114
What is the impact of mydriasis on depth and field of focus
Mydriasis causes a decrease in the depth of field and the depth of focus
115
What is the impact of miosis on depth and field of focus
increases both the depth of field and depth of focus
116
What is the impact of pupil size on spherical and chromatic aberration
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
What is the Stiles Crawford effect
is the observation that photoreceptors respond less to light entering through the periphery of the lens than through the centre
118
What are the 2 unpaired facial bones
The vomer and the mandible
119
What is the normal horizontal visual field of the eye in degrees
extends 90–100° temporally and 60° nasally, giving a horizontal field of 150–160°
120
What is the normal vertical visual field of the eye in degrees
it extends 70–80° inferiorly and 50–60° superiorly.
121
Where is the blind spot located relative to fixation
An absolute scotoma 10-20 degrees temporal to fixation.
122
Which telescope principle is useful for low vision aids
Gallilean. The objective and eyepiece lenses are separated by the difference between their focal lengths
123
What is stage 1 of Trachoma
conjunctival hyperaemia, early lymphoid hyperplasia, and oedema of the conjunctival stroma with infiltrating polymorphs
124
What is stage 2 of Trachoma
shows mature follicles and/or papillae, with peripheral corneal fibrovascular pannus formation
125
What is stage 3 of trachoma
the inflammatory tissue is replaced by fibrous material
126
What is stage 4 of trachoma
contraction of the palpebral conjunctival stroma, leading to entropion, trichiasis and corneal damage.
127
What are Langhans type giant cells
multinucleate giant cells which are formed from the fusion of epithelioid macrophages within a granuloma
128
What type of nuclei do Langhans type giant cells form
Horseshoe shape around the cell periphery
129
Viruses causing acute retinal necrosis
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
Does Acute retinal necrosis occur in immunocompetent individuals
Yes
131
Does Progressive outer retinal necrosis occur in immunocompromised individuals
Yes
132
Difference in presentation of ARN and PORN
both are believed to result from herpes virus infection, PORN does not have the associated vitritis, vasculitis or papillitis of ARN.
133
Prismatic effect of lens formula by decentration
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
Is VZV DNA/RNA virus
Double stranded DNA virus
135
How does Aciclovir work
inhibition of viral DNA synthesis.
136
How do Quinolones work
interact with bacterial DNA gyrase and topoisomerase IV, enzymes essential for bacterial DNA replication.
137
What is metastatic calcification
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
What is dystrophic calcifcation
occurs in normocalcaemia, typically in necrotic or hyalinised tissue. An example of this is a phthisical eye.
139
Which corneal layers does Band Keratopathy occur in
non-specific and involves calcification of the superficial stroma and Bowman’s layer in the interpalpebral cornea
140
What are the predominant cells found in acute inflammation
Neutrophils
141
What are the predominant cells found in chronic inflammation
predominantly macrophages and lymphocytes.
142
What is Bergemeister papillae
cone-like fibrous structure that is sometimes observed at the optic nerve head as a remnant of the hyaloid artery.
143
What is Mittendorf's dot
a small opacity that is sometimes observed on the posterior lens capsule at the point of anterior attachment of the hyaloid artery
144
What is a Forster-Fuch's spot
a pigmented macular scar associated with pathological myopia.
145
How long can steroids take to have effect
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
Which anaesthetic agents cause a rise in IOP
Suxamethonium
Ketamine
147
Which anaesthetic agents cause a fall in IOP
Inhalational anaesthetic agents
all intravenous induction agents except ketamine
148
How long does the effect of Atropine last
upto 7 days
149
How long does the effect of Homatropine last
6 hours to 4 days
150
How long does the effect of Cyclopentolate last
up to 24 hours
151
How long does the effect of Tropicamide last
4–6 hours
152
What is the inheritance pattern of Tay Sachs disease
autosomal recessive condition
153
What is the pathophysiology of Tay Sachs disease
progressive neurodegeneration caused by accumulation of GM2 ganglioside molecules.
154
Which gene mutation and chromosome is responsible for Tay Sach's disease
mutations of the HEXA gene on chromosome 15 which encodes a component of a lysosomal enzyme
155
What causes the oxygen dissociation curve to shift to the right
(reduced oxygen binding affinity) by increasing acidity and pCO2 (the Bohr effect), temperature and 2,3-DPG.
156
What is haemoglobin composed of
* 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
What is the ratio of photoreceptor cells to RPE cells at the posterior pole
45:1 at the posterior pole.
158
What is the rate of production of aqueous humour
approximately 2.5 μL/min
159
What are the properties of the image formed by a prism
Virtual
Erect
Displaced towards the apex
160
Which layers of the LGN do the contralateral fibres receive
1,4,6
161
Which layers of the LGN do the ipsilateral nerve fibres receive
2,3,5
162
Which nerve arises from the 1st pharyngeal arch
Trigeminal (V) – maxillary and mandibular branches
163
Which nerve arises from the 2nd pharyngeal arch
Facial (VII)
164
Which nerve arises from the 3rd pharyngeal arch
Glossopharyngeal (IX)
165
Which nerve arises from the 4th pharyngeal arch
Vagus (X) – superior laryngeal branch
166
Which nerve arises from the 6th pharyngeal arch
Vagus (X) – recurrent laryngeal branch
167
Disadvantages of viral vectors
* They can only carry a limited amount of genetic material, so some genes are too large
* They are immunogenic.
168
What is the standard error of the mean
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
What structures pass through Foramen ovale
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
