visual fields lec 1: kinetic perimetry Flashcards
1
Q
what is the definition of a visual field
A
all the space that an eye can see at any given time when gaze is fixed in one direction
2
Q
how far does the visual field extend superiorly
A
60 degrees. The anatomical limit is frontal orbit (brow)
3
Q
how far does the visual field extend inferiorly
A
70 degrees. The anatomical limit is cheek
4
Q
how far does the visual field extend nasally
A
60 degrees. The anatomical limit is nose
5
Q
how far does the visual field extent temporally
A
110 degrees. The anatomical limit is nasal retina
6
Q
what is the visual field limited by
A
facial features/anatomy e.g. forehead, eyebrows, nose, cheek bones
7
Q
what is considered the central visual field
A
30 degrees inside
8
Q
what is considered the peripheral visual field
A
30 degrees outside of the central visual field
9
Q
what does every point on the retina correspond to in the visual field
A
a certain direction in the visual field
10
Q
where does the nasal retina project
A
temporally
11
Q
where does the temporal retina project
A
nasally
12
Q
which orientation will the visual field be in relation to the retinal image on the eye
A
upside down and front to back
13
Q
if theres a problem with the inferior nasal retina, where will the visual field defect be
A
the superior temporal visual field
14
Q
which part of the fundus has the highest threshold sensitivity and why
A
the fovea, because it contains the highest density of cones
15
Q
which part of the fundus has no threshold sensitivity
A
the optic disc = blind spot
16
Q
what happens to threshold sensitivity as you go away from the fovea and why
A
threshold sensitivity reduces, as cone density reduces
17
Q
at which side of the visual field is the physiological blind spot and why
A
temporal visual field, as the optic disc is always at the nasal retina
18
Q
how wide is the physiological blind spot
A
5.5 degrees wide
19
Q
how far from fixation is the physiological blind spot
A
15 degrees
20
Q
how high in the visual field is the physiological blind spot
A
7.5 degrees
21
Q
how much below the midline is the physiological blind spot
A
1.5 degrees below
22
Q
which side will the physiological blind spot be on the right eye
A
right hand side
23
Q
which side will the physiological blind spot be on the left eye
A
left hand side
24
Q
which side will a patient’s right fundus be to the clinician
A
always on the clinicians left side
25
which side will a patient's left fundus be to the clinician
always on the clinicians right side
26
what is the measurement of visual field called
perimetry
27
what are the two types of perimetry
- kinetic
and
- static
28
what does the inside of the hill of vision represent
what you can see
29
what does the outside of the hill of vision represent
what you can't see
30
what does the height of the hill of vision represent
the threshold
31
what are the three types of manual kinetic perimetry
- Confrontation Visual Fields-Field Limits
- golmann bowl perimeter (both static and kinetic)
- Tangent screen
32
list the steps of how you will carry out manual kinetic perimetry
- stimulus moves from where the px can't see it, to where they can see it
- plot this onto a map
- stimulus is a fixed size and luminance
- eccentricity that the stimulus is seen as is then recorded at every 15 degrees, totalling 360 degrees
- points of equal sensitivity form together to make an isopter
- one isopter is not enough, so different isopters are measured using different stimulus sizes or light intensities
- to measure more closer to the centre fov, the procedure is repeated with smaller/lower luminance stimulus
- a minimum of 3 isopters is required for a good contour map of the visual field
33
what type of manual kinetic perimetry is gross perimetry
a gross screening test
| -field limits
34
list the steps of how to carry out gross perimetry
- px faces practitioner
- occlude one eye
- px told to constantly fixate on examiner's nose
- target held at 35cm from the patient's eye, outside the fov
- px report when they are first aware of the target
- carried out in uniform surroundings if possible
- target is moved at a constant velocity and in a imaginary arc
- once the px notices the target, make a mental note of it and continue moving the target to the centre, to see if they have a scotoma
- repeat in the 8 directions of gaze
- repeat with the other eye
35
list the 8 directions of gaze which gross perimetry must be carried out in
- superior
- superior temporal
- temporal
- inferior temporal
- inferior
- inferior nasal
- nasal
- superior nasal
36
where must the patient constantly fixate when carrying out gross perimetry
examiner's nose
37
at which distance is the target held from the patient with gross perimetry
35cm
38
list 4 advantages of gross perimetry
- quick
- cheap
- only method possible with young children or elderly with stroke
- detects gross field defects
39
list 4 disadvantages of gross perimetry
- useless for small areas of vision loss
- no control of stimulus luminance or contrast
- no control over background
- recognition of defect is dependent on judgement of practitioner
40
State how to set a patient up for
- projector
- head and chin rest
- response button (px presses when they see target)
- target - luminance and size controls can be specified (better than gross perimetry)
- chin rest positioning (can move around to get the red light on the fovea)
- occlude one eye -patch eye
- adjust the chin/head rest so the patients eye is in the centre of the telesope's field
- instruct the patient (to push the button when they just see the target)
- put up correct refractive correction
41
when will you always give a reading correction when carrying out perimetry
when measuring the inside 30 degrees of visual field
42
what makes up the reading correction
distance correction + reading addition
43
when will you NOT need to use a correction when carrying out perimetry and what is the exception to this
when measuring the outside 30 degrees of visual field
| unless the px has a +/- 8.00 DS refractive error
44
Select a trial lens that is LEAST likely to block patient's side vision. An improperly positioned trial lens can result in a
ring scotoma
45
what lens will you give when carrying out perimetry on a 60 year old px (absolute Presbyope) whose normal near add is +3.00D and distance rx is plano
+3.00D lens
- Add +3.00D to the distance correction for absolute and cyclopleged patients.
46
what lens will you give when carrying out perimetry on a 60 year old px whose normal near add is +3.00D and distance rx is -3.00D
give nothing
- Add +3.00D to the distance correction for absolute and cyclopleged patients.
47
what lens will you give when carrying out perimetry on a 60 year old px whose normal near add is +3.00D and distance rx is +3.00D
+6.00
- Add +3.00D to the distance correction for absolute and cyclopleged patients. +6.00D lens
48
what is the compensation lenses rule for any intermediate presybope?
add +1.50 sphere to their habitual add
49
What is the perimetry compensation lens rule for non -presbyope?
usually can use their customary distance correction
50
list the 7 steps of how to use the goldmann bowl perimeter
- select a stimulus e.g. v3
- move the stimulus in from the periphery, non-seeing to seeing
- record what they can see
- continue to move the stimulus to the centre, asking the patient to report if it disappears (to see any scotomas further in)
- repeat at 15/30 degrees intervals (30 degrees is adequate)
- repeat for atleast two other stimulus size/luminance combinations
- repeat these steps for the other eye
51
Which HFA does not need a trial lens?
HFA III. It uses a liquid lens and automatically loads patients correction based on data entered.
52
list 3 advantages of kinetic perimetry
- useful for detecting contraction of visual fields e.g. in retinitis pigmentosa
- useful for detecting neurological problems e.g. large visual field defects are detected such as a hemianopia
- useful in young children when automated versions are not possible
53
list 6 disadvantages of kinetic perimetry
- requires a skilled operator with manual perimetry
- results are operator dependent with manual perimetry
- difficult to quantify results with manual perimetry
- children/adults with a stroke will find manual perimetry easier (gross perimetry) as they move you can pause
- poor sensitivity for detecting scotomas with both manual and automated
54
what refractive correction will you use on a patient who has less than 1D of cyl
mean sphere/BVS (sph + 1/2 cyl)
55
when will you insert a cyl lens when carrying out perimetry
if the patient's cyl is above 1DC
56
Perimetry
a method used in optometry to assess a patient's visual field. It is ALWAYS performed monocularly.
57
What do perimeters measure?
the extent and sensitivity of a patient's visual field
58
A visual field defect tells you ______ the lesion is in the visual pathway.
where
59
Knowing where a lesion is in the visual pathway suggests what ________ the lesion
caused
60
patient reports a dim spot in their visual field. This is a _____
relative scotoma. A relative scotoma does not dip all the way down in the Island of Vision.
61
Height in the island of vision measures
sensitivity
62
Width (breadth) in the island of vision measures
extent of vision
63
Peak in the island of vision corresponds to the
fovea
64
physiologic blind spot corresponds to a pit that represents the patient's
optic nerve. This is an absolute scotoma.
65
Isopter
a horizontal slice as seen from above on a visual field Island of Vision. It represents a boundary of equal sensitivity. i.e. connect points with the same threshold.
66
A smaller and/or dimmer stimulus must come (Further or closer) to the fixation before it is seen
closer. Reason: the fixation has a high contrast sensitivity making it easier for dim and small lights to be picked up .
67
Indications for perimetry: History
```
Demylenating diseases (M/S)
Diabetes
Unexplained Headaches
Head injury
toxic medications: Plaquenil
```
68
Indications for perimetry: Ophthalmic problems
diplopia
poor vision on one side of the body
defect noted on confrontation visual fields
abnormal pupils or EOMS
Elevated IOP
unexplained reduction on best corrected visual acuity
69
Indications for perimetry: Comprehensive Exam
```
Pigment Dispersion Syndrome
Elevated IOP
Pseudoexfoliation syndrome
Funny looking disc:
large C/D ratio
drance hemorrhage
notching
papilledema
disc pallor
retinal disease
choroidal disease.
```
70
The background of a stimulus affects visual fields.
How does the hill of vision change in dark adaption?
it becomes flat because the relative peak of sensitivity at the fovea is lost
71
The background of the stimulus sets___________
the level of retinal light
72
A low photopic range is used most in perimeters
true
73
A sharp contrast of the stimulus against it's background is ___ to see.
easier.
74
A smaller stimulus size is _____ to see.
difficult to see because of spatial summation
75
A longer duration of stimulus is ____ to see
easier
76
The Humphrey automated perimeter shows a light that is ____than the critical duration and ____ than the eye movement latency (saccadic eye movement).
greater than; less than
