visual fields lec 1: kinetic perimetry Flashcards
what is the definition of a visual field
all the space that an eye can see at any given time
how far does the visual field extend superiorly
60 degrees
how far does the visual field extend inferiorly
75 degrees
how far does the visual field extend nasally
60 degrees
how far does the visual field extent temporally
100 degrees
what is the visual field limited by
facial features/anatomy e.g. forehead, eyebrows, nose, cheek bones
what is considered the central visual field
30 degrees inside
what is considered the peripheral visual field
30 degrees outside of the central visual field
what does every point on the retina correspond to in the visual field
a certain direction in the visual field
where does the nasal retina project
temporally
where does the temporal retina project
nasally
which orientation will the visual field be in relation to the retinal image on the eye
upside down and front to back
if theres a problem with the inferior nasal retina, where will the visual field defect be
the superior temporal visual field
which part of the fundus has the highest threshold sensitivity and why
the fovea, because it contains the highest density of cones
which part of the fundus has no threshold sensitivity
the optic disc = blind spot
what happens to threshold sensitivity as you go away from the fovea and why
threshold sensitivity reduces, as cone density reduces
at which side of the visual field is the physiological blind spot and why
temporal visual field, as the optic disc is always at the nasal retina
how wide is the physiological blind spot
5.5 degrees wide
how far from fixation is the physiological blind spot
15 degrees
how high in the visual field is the physiological blind spot
7.5 degrees
how much below the midline is the physiological blind spot
1.5 degrees below
which side will the physiological blind spot be on the right eye
right hand side
which side will the physiological blind spot be on the left eye
left hand side
which side will a patient’s right fundus be to the clinician
always on the clinicians left side
which side will a patient’s left fundus be to the clinician
always on the clinicians right side
what is the measurement of visual field called
perimetry
what are the two types of perimetry
- kinetic
and - static
what does the inside of the hill of vision represent
what you can see
what does the outside of the hill of vision represent
what you can’t see
what does the height of the hill of vision represent
the threshold
what are the two types of manual kinetic perimetry
- gross perimetry
- golmann perimeter
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
what type of manual kinetic perimetry is gross perimetry
a gross screening test
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
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
where must the patient constantly fixate when carrying out gross perimetry
examiner’s nose
at which distance is the target held from the patient with gross perimetry
35cm
list 4 advantages of gross perimetry
- quick
- cheap
- only method possible with young children or elderly with stroke
- detects gross field defects
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
where is the goldmann perimeter mainly used
in hospitals for kinetic perimetry
list the components of a goldmann perimeter and state how to use it
- 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)
- chart to draw isopter plots on
- pantoscopic arm (moves stimulus around)
- chin rest positioning (can move around to get the red light on the fovea)
- occlude one 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
when will you always give a reading correction when carrying out perimetry
when measuring the inside 30 degrees of visual field
what makes up the reading correction
distance correction + reading addition
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
for a full goldmann perimetry when and when not can spectacles be used and why
- specs can be used inside 30 degrees
- specs not used outside 30 degrees
because the rim gets in the way
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 plano
+3.00D lens
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
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
+6.00D lens
what is the near addition on the goldmanns table of near addition for a 40-44 year old
+1.50DS
what is the near addition on the goldmanns table of near addition for a 45-49 year old
+2.00DS
what is the near addition on the goldmanns table of near addition for a 50-54 year old
+2.50DS
what is the near addition on the goldmanns table of near addition for a 55 or year old or a cyclopeged px
+3.00DS
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
how does goldmann perimetry with octopus help with which settings should be used for which aged patients
it has aged matched normal values, for immediate judgement of normality i.e. landings tells you what should be used for what age
how is goldmann perimetry with octopus good at being a repeatable test
it has automatic repetition and follow up of kinetic examinations i.e. stimulus moves at the same speed. with a follow up button
how is the quantification of goldmann perimetry with octopus
measurement of isopters for the quantification of progression
which two types of kinetic testing does goldmann perimetry with octopus have
manual or automatic
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
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
what refractive correction will you use on a patient who has less than 1D of cyl
mean sphere/BVS (sph + 1/2 cyl)
when will you insert a cyl when carrying out perimetry
if the patient’s cyl is above 1DC