Part 2 > Exam Techniques > Flashcards

Exam Techniques Flashcards

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1
Q

Examples of VA measuring charts

A

Snellen
LogMAR (Bailey Lovie, ETDRS, Computer Charts)

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2
Q

What is distance VA directly related to?

A

the minimum angle
of separation (subtended at the nodal point of the eye) between two
objects that allow them to be perceived as distinct

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3
Q

What is the size of a pinhole

A

1mm

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4
Q

What distance if CF vision measured at

A

1m

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5
Q

What does LogMAR mean

A

acronym for the base-10 logarithm of the minimum angle of resolution (MAR) and refers to the ability to
resolve the elements of an optotype.

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6
Q

Distance for Snellen vs LogMAR measurement of VA

A

6m Snellen
4m LogMAR

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7
Q

What testing distance is the Bailey Lovie chart used at?

A

6m

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8
Q

What testing distance is the ETDRS chart used at?

A

4m

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9
Q

Which conditions reduce contrast sensitivity but maintain normal VA?

A

amblyopia, optic neuropathy, some cataracts, and higher-order aberrations

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10
Q

Examples of contrast sensitivity charts

A

Pelli Robson
Sinusoidal (sine wave) gratings
Spaeth Richman contrast sensitivity test (SPARCS)

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11
Q

How is the Pelli Robson test done

A

letter chart is viewed at 1 metre and consists of rows of letters of equal size (spatial frequency of 1 cycle per degree) but with decreasing contrast of
0.15 log units for groups of three letters. The patient
reads down the rows of letters until the lowest-resolvable
group of three is reached

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12
Q

What degree of field does the Amsler grid test?

A

20 degrees

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13
Q

How many Amsler charts are there and at what distance should they be kept

A

7 charts
33cm

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14
Q

Difference in observation between macula and ON disease on Amsler

A

Macula: wavy
ON: lines missing or faint but not distorted

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15
Q

What is the photostress test

A

visual pigments are bleached by light.
This causes a temporary state of retinal insensitivity perceived
by the patient as a scotoma.
PSRT is prolonged relative to the normal eye in macular disease (sometimes 50 seconds or more) but not in an
optic neuropathy.

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16
Q

What are the colour sensitivity ranges in nm for red/blue/green cones

A

red (protan): 549-570
blue (tritan): 414-424
green (deuteran): 522-539

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17
Q

Examples of colour vision tests

A

Ishihara
City University
Hardy-Rand-Rittler
Farnsworth Munsell 100 hue test

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18
Q

How many plates in the Ishihara chart

A

1 test, 16 plates

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19
Q

How is the city university colour test done?

A

10 plates, central colour, 4 peripheral colours subject asked to choose closest match

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20
Q

Hardy Rand Rittler- how is this done

A

Similar to Ishihara but detect all 3 congenital colour defects

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21
Q

How many caps in the FM100 hue test?

A

85 caps of different hues in 4 racks

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22
Q

What condition is the plus lens test positive in

A

Temporary hypermetropic shift may occur in some conditions
due to an elevation of the sensory retina – the classic example is
central serous chorioretinopathy (CSR). A +1.00-dioptre lens will demonstrate the phenomenon.

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23
Q

What are the extensions of the visual field hill in degrees

A

superior 50 degrees
nasal 60 degrees
inferior 70 degrees
temporal 90 degrees

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24
Q

relative vs absolute scotoma

A

area of reduced (‘relative’) or total (‘absolute’)
loss of vision surrounded by a seeing area.

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25
What is luminance
intensity or ‘brightness’ of a light stimulus, measured in apostilbs (asb). A higher intensity stimulus has a higher asb value; this is related inversely to sensitivity.
26
What is the background luminance of the HFA
31.5asb
27
What is SAP (standard automated perimetry)
Use static perimetry testing but can be dynamic
28
What are the types of glaucoma testing algorithms
Threshold Suprathreshold Fast algorithms
29
What is the threshold testing algorithm
Plotting the field comparing with age matched 'normal' values. Present a stimulus higher than the expected intensity, increased in decibels of 2dB if not seen. Good for monitoring glaucoma
30
What is the suprathreshold perimetry?
testing with stimuli of luminance above the expected normal threshold levels for an age matched population. Carried out rapidly- good for screening
31
What is the SITA algorithm
database of normal and glaucomatous fields to estimate threshold values and takes responses during the test into account to arrive at adjusted estimates throughout the test
32
Where do glaucoma field defects typically occur in the field?
centrally – within a 30° radius from the fixation point – so this is the area most commonly tested.
33
What does the 24-2 field mean
24’, denotes the extent in degrees to which the field is tested on the temporal side (to 30° on the nasal side). The number after the hyphen (2) describes the pattern of the points tested. 30-2 is an alternative.
34
What test is used to assess the peripheral field
Patterns that include central and peripheral points (e.g. FF-120) are typically limited to the assessment of neurological defects.
35
What reliability indices are important on a field test
False Negatives, False Positives over 15% significant (SITA) With full threshold Fixation losses over 20% and FP/FN over 33% significant
36
What is the total deviation on a field test result
difference between test derived threshold at a given point and normal sensitivity at this point for the general population correcting for age. Negative values indicate lower than normal sensitivity, positive values higher than normal
37
What is the pattern deviation on a field test result
derived from total deviation values adjusted for any generalised decrease in sensitivity in the overall field eg lens opacity. Demonstrates localised defects
38
What are the probability value plots
these plots of the total and pattern deviation are a representation of the percentage (<5% to <0.5%) of the normal population in whom the measured defect at each point would be expected. Darker symbols represent a greater likelihood that a defect is significant
39
What is Visual Field Index (VFI)
a measure of the patient’s overall visual field function expressed as a percentage, the normal age-adjusted value being 100%.
40
What is the mean deviation (MD)
gives an indication of the overall sensitivity of the field. It is derived from averaging the total deviation values.
41
What is PSD?
measure of focal loss or variability within the field and considers any generalized depression in the hill of vision. An increased PSD is therefore a more specific indicator of glaucomatous damage than MD.
42
What is the Glaucoma Hemifield Test
compares corresponding areas in the superior and inferior hemifields and relates only to glaucoma.
43
What is Short Wave Automated Perimetry (SWAP)
uses a blue stimulus on a yellow background. Sensitivity to blue light (mediated by blue cone photoreceptors) is adversely affected relatively early in glaucoma.
44
What is frequency doubling test (FDT)
arge diameter axon (magnocellular) ganglion cells appear to be preferentially lost in early glaucoma. The frequency-doubling illusion is produced when a low spatial frequency sinusoidal grating undergoes high temporal frequency counter phase flicker (>15 Hz)
45
What is microperimetry?
a visual field test that measures retinal sensitivity and fixation behaviour in patients with macular disease and focal glaucoma involving the central visual field. more sensitive than SAP in detecting subtle abnormality of visual function.
46
What is scleral scatter
Decenter slit beam laterally so light is incident on the limbus with microscope focused centrally. Light transmitted within cornea by total internal reflection. Corneal stromal lesions seen with this way.
47
What is retroillumination
Uses reflected light from the iris or fundus after pupil dilation to illuminate the cornea. Used to identify fine epithelial/endothelial changes, KP's, blood vessels
48
What is the correction factor for optic disc diameter with various Volk lenses
60D- x0.88-1 90D- x1.3 78D- x1.1
49
What is the mag and field in degrees provided by a 20D lens
magnifies x3 field 45 degrees
50
What is the mag and field in degrees provided by a 28D lens
magnifies x2.27, field 53 degrees
51
What principle is the GAT based on
Imbert Fick. Pressure equals force over area when flattened area is 3.06mm
52
What corneal thickness does GAT assume
520microns
53
Are patients with a low or high hysteresis likely to proceed with glaucoma
lower
54
Examples of 4 mirror gonioprisms
Zeiss Posner Sussman (no handle) Good for indentation gonioscopy
55
How is indentation gonioscopy done
gently pressing the lens posteriorly against the cornea forcing aqueous into angle pushing peripheral iris posteriorly. if angle closed by apposition between iris cornea- forced open, if PAS, remain closed
56
What are some examples of Direct goniolenses
Koeppe Medical Workshop Barkan Swan Jacob
57
Difference in anatomical structures of canal based structure vs suprachoroidal surgery
canal based- trabecular meshwork anteriorly suprachoroidal- ciliary body band posteriorly
58
What does Schwalbe line delineate?
Most anterior angle structure demarcating peripheral termination of DM and anterior limit of trabeculum
59
What is Sampaolesi line
pigment line deposited anterior to Schwalbe line.
60
What is the corneal wedge
used to locate an inconspicuous Schwalbe line. Using a narrow slit beam two distinct corneal reflections seen, one on inner and outer corneal surface. Outer reflection will arc round across corneoscleral interface due to sclera being opaque to meet inner reflection at apex of corneal wedge that coincides with Schwalbe's line
61
What is the trabeculum
Extends from Schwalbe line to scleral spur with a width of 600 microns. Younger patients has a ground glass appearance. Anterior non functional part adjacent to Schwalbe line is white. Posterior functional part lies adjacent to Scleral spur has a grey blue appearance.
62
Iris process vs PAS
Small extensions of anterior surface of iris inserting at level of scleral spur covering ciliary body to an extent. Present in 1/3rd eyes. Dont confuse with PAS which are extending more anteriorly more substantial
63
PAS Causes
PACG AAU ICE syndrome
64
NV causes
NVG Fuchs Heterochromic Cyclitis Chronic AU
65
Hyperpigmentation angle causes
Physiological variant PDS PXF Pseudophakic Pigment dispersion Blunt ocular trauma Anterior uveitis After PACG After YAG PI Iris/angle melanoma/naevus Iris pigment epithelial cyst Naevus of ota
66
What can you see in the angle post trauma
Angle recession Trabecular dialysis Cyclodialysis Foreign bodies
67
What can blood in the Schlemm canal mean?
Physiological variant Carotid-cavernous fistula and dural shunt Sturge Weber syndrome Obstruction of SVC
68
Normal CCT
540 +/- 30 microns
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