Examination Techniques Flashcards
What is distance visual acuity directly related to?
The minimum
angle of separation (subtended at the nodal point of the eye)
between two objects that allow them to be perceived as distinct.
What is normal monocular VA
Equates to 6/6 (metric notation; 20/20 in non-metric ‘English’ notation) on Snellen testing.
Normal corrected VA in young adults is often superior to 6/6.
What is Best corrected VA
denotes the level achieved with
optimal refractive correction.
What is pinhole VA
pinhole (PH) aperture compensates for the
effect of refractive error, and consists of an opaque occluder
perforated by one or more holes of about 1 mm diameter
PH acuity in patients with macular disease and
posterior lens opacities may be worse than with spectacle cor-
rection.
If the VA is less than 6/6 Snellen equivalent, testing is
repeated using a pinhole aperture.
What is Binocular VA
usually superior to the better monocular VA of each eye, at least where both eyes have roughly equal vision.
What does CF vision mean
denotes that the patient is
able to tell how many fingers the examiner is holding up at a
specified distance usually 1 metre.
What is HM vision
the ability to distinguish whether the examiner’s hand is moving when held just in front of the patient.
What is PL vision
the patient can discern only light
(e.g. pen torch), but no shapes or movement. Careful occlusion of the other eye is necessary. If poor vision is due solely to a dense media opacity such as cataract, the patient should readily be able to determine the direction from which the light
is being projected
What is log MAR
an 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
Thus, if a letter on the
6/6 (20/20) equivalent line subtends 5′ of arc, and each limb of
the letter has an angular width of 1′, a MAR of 1′ is needed for resolution. For the 6/12 (20/40) line, the MAR is 2′, and for the
6/60 (20/200) line it is 10′
What is the value of each letter on the LogMAR chart
0.02
Examples of LogMAR Charts
1) Bailey- Lovie Chart
2) ETDRS chart
3) Computer charts
At what distance is the Bailey Lovie chart read from?
6m
At what distance is the ETDRS chart read from?
4m
Is macula disease better tested with distance or near vision?
Near vision
Which conditions reduce contrast sensitivity but preserve VA
1) Amblyopia
2) Optic Neuropathy
3) Some cataracts
4) Higher order aberrations
What is the Pelli Robson chart
contrast sensitivity 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.
What is the principle of contrast sensitivity testing?
It is a measure of the ability of the
visual system to distinguish an object against its background.
A light grey
letter will be less well seen against a white background than a
black letter.
Examples of contrast sensitivity tests
1) Pelli-Robson chart
2) Sinusoidal (sine wave) gratings
3) Spaeth Richman Contrast Sensitivity test (SPARCS)
How is sine wave grating contrast sensitivity test performed
require the test subject to
view a sequence of increasingly lower contrast gratings.
How is near VA tested?
A range of near vision charts (including logMAR and ETDRS versions) or a test type book can be used. The book or chart is held at a comfortable reading distance and this is measured and noted. The patient wears any necessary distance correction
together with a presbyopia correction if applicable (usually their own reading spectacles). The smallest type legible is recorded for each eye individually and then using both eyes together
What is the Amsler grid used for?
evaluates the 20° of the visual field centred on
fixation. It is principally useful in screening for and monitoring macular disease, but will also demonstrate central visual field defects originating elsewhere. Patients with a substantial risk
of choroidal neovascularization (CNV) should be provided with an Amsler grid for regular use at home.
How many types of Amsler grid are there?
7
At what distance from the eyes should the Amsler grid be held?
33cm
How to differentiate macula vs optic neuropathy on an Amsler grid?
Patients with macular disease often report
that the lines are wavy whereas those with optic neuropathy tend to remark that some of the lines are missing or faint but not distorted.
Types of Amsler grid charts
1) White grid black background
2) Similar to chart 1 with diagonal lines to aid fixation
3) Similar to chart 1 but with red squares
4) Random dots
5) Horizontal lines detecting metamorphopsia along specific meridians
6) Similar to chart 5 but with a white background and lines closer together
7) Fine central grid each square subtending an angle of half degree
What is the light brightness comparison test used for?
This is a test of optic nerve function, which is usually normal in
early and moderate retinal disease.
What is photostress testing?
a gross test of dark adaptation in which the visual pigments are bleached by light. This causes a temporary state of retinal insensitivity perceived by the patient as a scotoma.
What does the photostress test, test?
detecting maculopathy when ophthalmoscopy is equivocal, as in mild cystoid macular
oedema or central serous retinopathy. It may also differentiate
visual loss caused by macular disease from that caused by an
optic nerve lesion.
What is the blue retinal cone peak sensitivity?
414-424nm
What is the green retinal cone peak sensitivity?
522-539nm
What is the red retinal cone peak sensitivity?
549-570nm
What is protanomaly?
red cone weakness
What is protanopia?
red cone absence
What are people with red-green deficiency called?
Protanomalous- due to abnormality of red sensitive cones
What are people with an abnormality of green sensitive cones called?
Deuteranomalous
What are people with blue green deficiency called?
Tritanomalous
What colour defect does acquired macula disease produce
Blue- yellow defects
What colour defect do optic nerve lesions produce
Red-green defects
What defects does the Ishihara test screen for?
Congenital protan and deuteran defects (red-green) colour vision defect
Examples of colour vision tests?
Ishihara test
City university test
Hardy Rand Rittler test
Farnsworth- Munsell 100 hue test
What is the photostress test?
1) BCVA measured first
2) The patient looks at a light held about 3 cm away from the eye, for about 10 seconds;
3) The photostress recovery time is the time taken to read any three letters of the pre-test acuity line and is normally between 15 and 30 seconds
What is the hill of increasing sensitivity of a visual field
1) 50 deg superiorly
2) 60 deg nasally
3) 70 deg inferiorly
4) 90 deg temporally