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CEVS IV > visual fields lec 1: kinetic perimetry > Flashcards

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

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2
Q

how far does the visual field extend superiorly

A

60 degrees. The anatomical limit is frontal orbit (brow)

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3
Q

how far does the visual field extend inferiorly

A

70 degrees. The anatomical limit is cheek

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4
Q

how far does the visual field extend nasally

A

60 degrees. The anatomical limit is nose

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5
Q

how far does the visual field extent temporally

A

110 degrees. The anatomical limit is nasal retina

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6
Q

what is the visual field limited by

A

facial features/anatomy e.g. forehead, eyebrows, nose, cheek bones

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7
Q

what is considered the central visual field

A

30 degrees inside

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8
Q

what is considered the peripheral visual field

A

30 degrees outside of the central visual field

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9
Q

what does every point on the retina correspond to in the visual field

A

a certain direction in the visual field

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10
Q

where does the nasal retina project

A

temporally

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11
Q

where does the temporal retina project

A

nasally

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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

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13
Q

if theres a problem with the inferior nasal retina, where will the visual field defect be

A

the superior temporal visual field

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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

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15
Q

which part of the fundus has no threshold sensitivity

A

the optic disc = blind spot

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16
Q

what happens to threshold sensitivity as you go away from the fovea and why

A

threshold sensitivity reduces, as cone density reduces

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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

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18
Q

how wide is the physiological blind spot

A

5.5 degrees wide

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19
Q

how far from fixation is the physiological blind spot

A

15 degrees

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20
Q

how high in the visual field is the physiological blind spot

A

7.5 degrees

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21
Q

how much below the midline is the physiological blind spot

A

1.5 degrees below

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22
Q

which side will the physiological blind spot be on the right eye

A

right hand side

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23
Q

which side will the physiological blind spot be on the left eye

A

left hand side

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24
Q

which side will a patient’s right fundus be to the clinician

A

always on the clinicians left side

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25
Q

which side will a patient’s left fundus be to the clinician

A

always on the clinicians right side

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26
Q

what is the measurement of visual field called

A

perimetry

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27
Q

what are the two types of perimetry

A
  • kinetic
    and
  • static
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28
Q

what does the inside of the hill of vision represent

A

what you can see

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29
Q

what does the outside of the hill of vision represent

A

what you can’t see

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30
Q

what does the height of the hill of vision represent

A

the threshold

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31
Q

what are the three types of manual kinetic perimetry

A
  • Confrontation Visual Fields-Field Limits
  • golmann bowl perimeter (both static and kinetic)
  • Tangent screen
32
Q

list the steps of how you will carry out manual kinetic perimetry

A
  • 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
Q

what type of manual kinetic perimetry is gross perimetry

A

a gross screening test

-field limits

34
Q

list the steps of how to carry out gross perimetry

A
  • 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
Q

list the 8 directions of gaze which gross perimetry must be carried out in

A
  • superior
  • superior temporal
  • temporal
  • inferior temporal
  • inferior
  • inferior nasal
  • nasal
  • superior nasal
36
Q

where must the patient constantly fixate when carrying out gross perimetry

A

examiner’s nose

37
Q

at which distance is the target held from the patient with gross perimetry

A

35cm

38
Q

list 4 advantages of gross perimetry

A
  • quick
  • cheap
  • only method possible with young children or elderly with stroke
  • detects gross field defects
39
Q

list 4 disadvantages of gross perimetry

A
  • 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
Q

State how to set a patient up for

A
  • 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
Q

when will you always give a reading correction when carrying out perimetry

A

when measuring the inside 30 degrees of visual field

42
Q

what makes up the reading correction

A

distance correction + reading addition

43
Q

when will you NOT need to use a correction when carrying out perimetry and what is the exception to this

A

when measuring the outside 30 degrees of visual field

unless the px has a +/- 8.00 DS refractive error

44
Q

Select a trial lens that is LEAST likely to block patient’s side vision. An improperly positioned trial lens can result in a

A

ring scotoma

45
Q

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

A

+3.00D lens

  • Add +3.00D to the distance correction for absolute and cyclopleged patients.
46
Q

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

A

give nothing

  • Add +3.00D to the distance correction for absolute and cyclopleged patients.
47
Q

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

A

+6.00

  • Add +3.00D to the distance correction for absolute and cyclopleged patients. +6.00D lens
48
Q

what is the compensation lenses rule for any intermediate presybope?

A

add +1.50 sphere to their habitual add

49
Q

What is the perimetry compensation lens rule for non -presbyope?

A

usually can use their customary distance correction

50
Q

list the 7 steps of how to use the goldmann bowl perimeter

A
  • 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
Q

Which HFA does not need a trial lens?

A

HFA III. It uses a liquid lens and automatically loads patients correction based on data entered.

52
Q

list 3 advantages of kinetic perimetry

A
  • 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
Q

list 6 disadvantages of kinetic perimetry

A
  • 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
Q

what refractive correction will you use on a patient who has less than 1D of cyl

A

mean sphere/BVS (sph + 1/2 cyl)

55
Q

when will you insert a cyl lens when carrying out perimetry

A

if the patient’s cyl is above 1DC

56
Q

Perimetry

A

a method used in optometry to assess a patient’s visual field. It is ALWAYS performed monocularly.

57
Q

What do perimeters measure?

A

the extent and sensitivity of a patient’s visual field

58
Q

A visual field defect tells you ______ the lesion is in the visual pathway.

A

where

59
Q

Knowing where a lesion is in the visual pathway suggests what ________ the lesion

A

caused

60
Q

patient reports a dim spot in their visual field. This is a _____

A

relative scotoma. A relative scotoma does not dip all the way down in the Island of Vision.

61
Q

Height in the island of vision measures

A

sensitivity

62
Q

Width (breadth) in the island of vision measures

A

extent of vision

63
Q

Peak in the island of vision corresponds to the

A

fovea

64
Q

physiologic blind spot corresponds to a pit that represents the patient’s

A

optic nerve. This is an absolute scotoma.

65
Q

Isopter

A

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
Q

A smaller and/or dimmer stimulus must come (Further or closer) to the fixation before it is seen

A

closer. Reason: the fixation has a high contrast sensitivity making it easier for dim and small lights to be picked up .

67
Q

Indications for perimetry: History

A 
Demylenating diseases (M/S)
Diabetes
Unexplained Headaches
Head injury 
toxic medications: Plaquenil
68
Q

Indications for perimetry: Ophthalmic problems

A

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
Q

Indications for perimetry: Comprehensive Exam

A 
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
Q

The background of a stimulus affects visual fields.

How does the hill of vision change in dark adaption?

A

it becomes flat because the relative peak of sensitivity at the fovea is lost

71
Q

The background of the stimulus sets___________

A

the level of retinal light

72
Q

A low photopic range is used most in perimeters

A

true

73
Q

A sharp contrast of the stimulus against it’s background is ___ to see.

A

easier.

74
Q

A smaller stimulus size is _____ to see.

A

difficult to see because of spatial summation

75
Q

A longer duration of stimulus is ____ to see

A

easier

76
Q

The Humphrey automated perimeter shows a light that is ____than the critical duration and ____ than the eye movement latency (saccadic eye movement).

A

greater than; less than

CEVS IV (3 decks)

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