Paper 4 Flashcards
1
Q
What is the main source of image imperfection when the pupil is small
A
Diffraction
2
Q
What is the Stiles Crawford effect
A
refers to the directional sensitivity of the cone photoreceptors
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.
4
Q
How many degrees is 1 prism dioptre
A
1/2 degree
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).
6
Q
What is static refraction
A
The dioptric power of the resting eye
7
Q
What is dynamic refraction
A
The dioptric power of the accommodated eye
8
Q
What range of dioptric power does a pinhole correct
A
+4 to -4
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
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.
11
Q
In a standard loupe where is the object situated
A
between the first principal focus and the lens.
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.
13
Q
In indirect ophthalmoscopy how much magnification does the +13D lens create
A
approximately 5x magnification
14
Q
In indirect ophthalmoscopy how much magnification does the +20D lens create
A
approximately x3 magnification
15
Q
Is the peripheral cornea flatter than the central cornea
A
YES
16
Q
What diameter of the central cornea is used for vision
A
4mm
17
Q
What is the resulting image of a Galilean telescope
A
real, inverted, and magnified.
18
Q
Which purkinje samson images are used to measure AC depth
A
Images 2 and 3
19
Q
What wavelength of light does the Nd YAG laser emit
A
1064nm
20
Q
How many meibomian glands are found on the upper lid
A
30
21
Q
AP diameter of the eye
A
24mm
22
Q
Vertical diameter of the eye
A
23mm
23
Q
Horizontal diameter of the eye
A
23.5mm
24
Q
Longest rectus muscle tendon length
A
Lateral Rectus 8.8mm
25
Shortest rectus muscle tendon length
Medial 3.7mm
26
What are the anterior and posterior boundaries of the anterior cranial fossa
Anterior->frontal bone
Posteriorly-> sharp lesser wing of sphenoid.
27
What volume does the vitreous occupy in the eyeball
4/5 (80%)
28
What are the 3 axes of Fick
Vertical abduction and adduction
Transverse elevation and depression
Sagittal extorsion and intorsion
29
Where is the CN4 nucleus located
in the midbrain at the level of the inferior colliculus
30
What percentage of optic nerve axons originate from midget ganglion cells
90%- associated with cones
31
What percentage of ganglion cells associated with rods from the peripheral retina
10%- associated with rods
32
Which EOM are visible at week 5
lateral rectus,
superior rectus,
levator palpebrae superioris
33
Which EOM are visible at week 6
superior oblique
medial rectus
34
Which EOM are visible after week 6
Inferior oblique
Inferior rectus
35
Order of lacrimal drainage structures
From eye to nose, are as follows:
superior and inferior puncta,
superior and inferior canaliculi,
common canaliculus,
nasolacrimal sac,
nasolacrimal duct,
plica lacrimalis.
36
How frequently do the cell layers of the corneal epithelium turn over
Every 7-10 days
37
What are the 2 remnants of the fetal hyaloid artery
Bergmeister’s papilla- at the optic disc
Mittendorf’s dot - posterior lens capsule
38
What is the percentage of oxygen saturation of the venous blood of the choroid
over 90%
39
What happens to lens nucleus thickness in accommodation
thickness of the nucleus increases but the thickness of the cortex does not change
40
What is the equivalence of 1 apostilb in lumen/m2
1lumen/m2
41
What is the equivalence of 1 lux
1 metre-candela
42
What is the equivalence of 1 lambert
1 candela at 1 cm distance for a perfectly diffusing light source on a surface at 1 cm.
43
How many muscle fibres per motor unit are present in the human body
80-100
44
What does the Frank Starling mechanism of the heart state
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
What is the dorsal respiratory group responsible for
Inspiration
46
What is the ventral respiratory group responsible for
Expiration
47
What does the pneumotaxic centre govern
rate and depth of breathing
48
What does the smooth endoplasmic reticulum primarily secrete
site of synthesis of lipids, triglycerides, and steroids
49
Which cells of the eye is the smooth endoplasmic reticulum primarily found
RPE
Meibomian gland cells
50
What kind of cells is the rough endoplasmic reticulum found in
highly developed in secretory cells, including the lacrimal gland acinar cell.
51
What wavelength light does the cornea absorb
Short wavelength light
52
Where are hard and soft drusen located in the retina
between the retinal pigment epithelium (RPE) basement membrane and Bruch’s membrane
53
Where are basal linear deposits located in the retina
between the RPE basement membrane and RPE cell cytoplasm.
54
What is the commonest protozoal parasite to infect the eye
Toxoplasma gondii
55
What are the classic tetrad of features of infection with Toxoplasma gondii
meningoencephalitis,
hydrocephalus,
intracranial
calcification,
retinochoroiditis
56
Risk factors for primary angle closure glaucoma
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
What is the pathophysiology of Cogan dystrophy
degeneration of cells with cyst formation, causing an unstable corneal epithelium.
58
What are some features found in ARN but not PORN
retinal vasculitis,
papillitis.
THESE ARE NOT FOUND IN PORN
59
What is endophytic growth in retinoblastoma
into the vitreous
60
What is exophytic growth in retinoblastoma
into the subretinal space
61
What are Homer Wright Rosettes
a multilayered circle of nuclei surrounding eosinophilic fibrillate material, with no lumen or internal limiting membrane.
62
What are Fleurettes
primitive photoreceptor bodies, arranged in a ‘fleur de lys’ shape
63
Which HHV virus causes Kaposi Sarcoma
HHV8
64
Which Chlamydia serotypes cause urogenital infections
Serotypes D-K
65
Which immune cells feature several mitochondria and ribosomes
Basophils
66
By what percentage do beta blockers reduce IOP
50%
67
What class of drug is apraclonidine
Parasympathetic agonist
68
How does Tacrolimus work
inhibits interleukin-2.
69
How does Mycophenolate work
blocks the de novo pathway of purine synthesis (selective for lymphocytes)
70
What does Prostaglandin I2 cause
vasodilation and reduces platelet adhesion.
71
What does Prostaglandin F2 alpha cause
bronchial smooth muscle contraction
72
What does Prostaglandin E2 cause
vasodilation, bronchodilation, uterine contraction, fever, macrophage activation, and release of pituitary hormones, adrenal cortex steroids, and insulin from the pancreas
73
What does Leukotriene B4 cause
aggregation of neutrophils, chemotaxis, and stimulation of phospholipase A2
74
What does Leukotriene D4 cause
contraction of smooth muscle, vasoconstriction, and bronchoconstriction
75
What does Thromboxane A2 cause
vasoconstriction, bronchoconstriction, and platelet aggregation
76
What does the Hardy Weinburg equilibrium assert
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
Which cells are affected in retinoblastoma
Primitive photoreceptor cells
78
Does retinoblastoma have a preference for affecting males/females
NO- Males females equally affected
79
What does Traquir analogy of the visual field demonstrate
the visual field is ‘an island of vision surrounded by a sea of darkness’.
80
In Traquir analogy what is the hill of vision
the fovea represents the peak of the ‘hill’
81
In Traquair analogy what does the ground level represent
the visual field extends 50° superiorly, 60° nasally, 70° inferiorly, and 90° temporally
82
What is the pattern standard deviation
a measure of variability or focal loss within the visual field. PSD takes into account any generalised depression
83
What is a high PSD indicative of
a high PSD is more indicative of glaucomatous field loss than mean deviation, which is simply a measure of overall field loss.
84
What is the field of view of a fundus photograph
30-35 degrees
85
In FFA what is a window defect most likely caused by
RPE defect conditions eg macula hole/RPE atrophy
86
What cell layers of the retina are hyperreflective on OCT
the nerve fibre layer and inner and outer plexiform layers are typically hyperreflective
87
What cell layers of the retina are hyporeflective on OCT
The ganglion cell layer and inner and outer nuclear layers
88
What layers are lost in Geographic atrophy
an advanced form of dry AMD associated with atrophy of the outer retina, RPE, and choriocapillaris, leading to permanent loss in vision
89
In ocular Ultrasonography what does the gain control do
adjust the amplification of the reflected signal. It does not change the amount
of ultrasonic energy emitted from the probe
90
What are the features of choroidal melanoma on A-scan
typically show medium to low internal reflectivity.
91
What are the features of choroidal melanoma on B scan
appear dome-shaped; other characteristics include an acoustically hollow zone within the melanoma, subretinal fluid, and choroidal excavation.
92
What are the features of optic disc drusen on B scan
their high reflectivity
93
What are the features of posterior scleritis on B scan
well-defined, thickened sclera and fluid in Tenon’s space
94
What is the rod response ERG
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
What is the maximal ERG
obtained from dark adapted eyes using a bright white flash is a mixed rod and cone
response
96
Which conditions reduce A and B waves on ERG
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
What ERG response does X linked retinoschisis cause
cause a normal a-wave and reduced scotopic b-wave, also termed an ‘electronegative’ response
98
How is the ARR calculated
control event rate minus experimental event rate
99
What does the solid vertical line on a Forest plot represent
Line of no effect
100
What does the size of the box on a Forest plot represent
individual study power (and therefore sample size)
101
What does the horizontal whiskers on a Forest plot represent
indicate the confidence intervals per individual study
102
WHO criteria for mild distance visual impairment
visual acuity worse than 6/12 to 6/18.
103
WHO criteria for moderate distance visual impairment
visual acuity worse than 6/18 to 6/60.
104
WHO criteria for severe distance visual impairment
visual acuity worse than 6/60 to 3/60
105
WHO criteria for blindness
visual acuity worse than 3/60
106
WHO criteria for near vision impairment
Near visual acuity worse than N6 or M.08 at 40 cm.
107
What is attrition bias
due to unequal loss of participants from different arms of a trial
108
What is selection bias
caused by failure to achieve proper randomisation during participant selection
109
What is confirmation bias
caused by the tendency to search for or favour information that confirms prior beliefs
