COA visual field and reading notes in student

Welcome

1. Visual Fields
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2. Visual Field/ Perimetry
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•Is a procedure for measurement of an
individual’s visual field; what they are able
to see peripherally as well as Centrally. It
aims to:
–Detect field defects (screening programs)
–Quantify the size, shape, and depth of all
defects

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≈ ≈ 60º60º
100-110 100-110 ºº
70-75 70-75 ºº
≈≈ 60 º60 º
Central field
Peripheral field

4. Techniques of perimetry
Kinetic
Static
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5. Techniques of Perimetry
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Kinetic - a moving stimulus of fixed intensity and size is
moved at a constant rate from non– seeing to seeing regions,
identifying points of initial perception.
These points map out an isopter, a defined locus of identical
retinal sensitivity.

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isopter
Fixation point

7. Techniques of Perimetry Cont…
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Static - a stationary stimulus at a fixed location is gradually
increased in intensity or size until the stimulus is initially
perceived.
This initial perception determines the retinal threshold
sensitivity at that point and the presence and depth of a
scotoma may thereby be determined.
Static testing at various points along a meridian defines a
profile, or vertical cross-section of the hill of vision

8. Clinical testing methods
•Central fields- Below 30°
•Peripheral fields – Above 30° to 360°
Central Fields:
Amsler’s grid
Peripheral Fields:
Confrontation method
Goldmann perimeter
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Humphrey visual field
analyzer

10. Systemic interpretation of
visual field printout
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1.What type of visual field test was performed?
2.What are the patient demographics and clinical characteristics?
3.How reliable is the visual field?
4.Is the visual field abnormal?
5.What is the pattern of abnormality?
6.Is the field worsening?
7.Is the abnormality or worsening due to disease or artifact?

11. Confrontation test
•Position yourself in front of the patient, facing her/him with
your face level with that of her/his, at a distance of about a
metre.
•A comparison of examiner and patient fields is made, the
assumption being that you, as the examiner, have normal
visual fields (this is another reason why you should undergo
visual field testing yourself).
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12. •First test the binocular visual field and then
test each eye separately.
•A defect is detected by the absence of a
patient response to the showing of a target,
when the target is visible to you.
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13. •Ask the patient to stare directly and steadily into
your eyes.
•Allow the patient to rest and try again if they find it
difficult to look at you so directly.
•Check that the patient can look steadily at your eyes
while you look steadily at theirs.
• Ask the patient whether any part of your face is
missing or indistinct.
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14. •To test the patient’s right hemi-field and
upper and lower quadrants, repeat the finger-
counting test using your left hand, starting just
to the left of your face and moving up and left
and then down and left.
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15. •A useful, additional test to perform in patients with a
suspected homonymous hemianopsia (i.e. loss of either
the right or left field of vision in both eyes, often from a
stroke) is to test for sensory inattention.
•Hold both hands up and wiggle the fingers of the right
hand, followed by those of the left hand in each hemi-
field.
•If the patient sees the moving fingers, then wiggle one
finger of each hand at the same time – if the patient can
only see movement on one side then they may have a
subtle hemianopia
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16. •Testing each eye to confrontation
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17. •Ask the patient to cover their own eye with
the palm of their hand (not their fingers, as it
is easy to peep between fingers).
•Remember that you should close your eyes in
turn too, so that you are comparing the field
in your right eye with the field of the patient’s
left eye
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18. •Do the finger counting test first (static
testing).
•Be sure to test on both the left and the right
for each eye tested.
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19. Next, bring your target finger from the far
periphery in towards the central region
(kinetic testing).
Ask the patient to say when they first see the
target.
Repeat from several different directions,
ensuring that the full 360° for each eye is
tested.
The examiner should remember to perform
kinetic testing at a speed appropriate for the
patient’s responses.
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20. •Next, test the peripheral field with a white-headed
neurological pin (beyond a central 30° radius) and the
central field with a red-headed neurological pin (within a
30° radius).
•Testing with neurological pin targets gives much more
accurate results than testing with fingers, and can detect
earlier visual field loss.
• Red-headed neurological pins are also useful for
assessing the size of the blind spot (e.g., with
papilloedema), again by comparing the size of your blind
spot with that of the patient’s
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21. •In addition, red-headed neurological pins can
be used to test for red-desaturation in early
optic nerve disease.
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22. Amsler chart testing
•A printed grid (Amsler chart) can be used to
detect subtle central defects (fairly
common in patients with glaucoma) –
especially those with normal tension
glaucoma).
•Test one eye at a time, correcting for any
near refractive errors.
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23. •Patients should hold the chart at a
comfortable reading distance from their
uncovered eye, and stare at the central spot
of the grid.
•Ask them to identify and then point out any
areas where the grid is missing or distorted.
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24. •Missing areas may suggest paracentral
glaucomatous visual field loss, whereas
distortion is more common with macular
disorders
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26. •Amsler grid, when viewed by someone with
normal central vision (a)
•Amsler grid, when viewed by people with a
problem with their central visual field (b and
c)
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