O2B Visual Fields
Card Set Information
O2B Visual Fields
visual fields optometry
Why do we assess visual fields?
Assess peripheral vision
Assess the integrity of the visual pathway
Diagnose ocular and neurological diseases
Monitor the progression of ocular diseases
What are the indications of the assessment of visual fields?
Glaucoma / suspicion of glaucoma
Reduced visual acuity
Benign optic disc conditions
Retinal disorders – inflammations and dystrophies
Assessing fitness to drive
Evaluating sport fitness especially elite levels
What are the advantages of visual field assessments?
Direct assessment of visual function
More than just central vision
Can typically detect cheating
Repeatable examination techniques – good for monitoring progression
Good for differential diagnoses of diseases – typically obtain characteristic VF losses
Extra income for practitioner
What are the disadvantages of visual field assessments?
Machines not portable
Subjective assessment by patient
What are the bones that restrict vision?
Superior margin = frontal
Inferior margin = maxillary
Medial margin = frontal lacrimal and maxillary
Temporal margin = frontal and zygomatic
How does sensitivity vary within the visual field?
nature of stimulus test
What are the characteristics of the island of vision?
steeper on the nasally
What is the hill of vision?
2D section of the island of vision
0-5- steep slope at fovea
5-40- flatter central VF
>40- steep edge of VF
Diffuse visual field loss / Depression – generally caused by pre-retinal opacities e.g. corneal oedema, cataract
Gap in HOV?
Focal visual field loss - An area of reduced sensitivity surrounded by an area of normal sensitivity – focal point of damage in retina or visual pathway
Visual field contraction – caused by conditions which affect the peripheral retina
What are the manual ways of VF testing?
What are the advantages of manually testing VF?
Fast and flexible
Good for measuring severe VF loss or measuring absolute loss
Good for multiple handicapped
Excellent in low vision and neurological cases
What are the disadvantages of manually testing VF?
It’s not standardized
Not good for measuring the depth of scotoma
Can’t pick up shallow scotomas well
Not as good in quantifying central field
Requires an experienced clinician
What are confrontational fields?
Relatively gross method used to screen for the presence of unsuspected field defects- insensitive
compares px VF to practioners
What are the types of confrontational field tests?
: dynamic movement of small target in VF until seen
: dynamic movement of fingers in VF until seen
What is a manual VF test?
stim presentation and manipulation is controlled by practioner
What is a kinetic VF examination strategy?
a stimulus of constant size and shape is moved across VF
moved frmo periphery until seen
What is a static VF examination strategy?
stim apears in stationary loactions but may change in characteristics
What is a threshold exam?
estimate threshod of eye at different locations
Whats is a suprathreshold exam?
present stim above threshold/ recrod if seen
What is a tangent screen?
more sensitive than confrontational
Non-reflective black screen
Small central white fixation target
Concentric circles stitched at
A selection of targets
How does the tangent screen work?
px sits 1m away-tests 25-30deg
target is moved from periphery until seen- scotomas
What is an Amsler grid?
black lines on white bg
viewed at 28cm, one box= one degree
wavy lines/missing lines
What area of visual space does the amsler grid test?
10 degree either side of fixation
What does the amsler grid primarily test and how?
: AMD, diabetic maculopathy, central serous retinopathy
sees wavy lines or lines missing
What is the Goldmann bowl perimeter?
Stimuli projected onto the surface of a bowl
Stimulus can becontrolled by the practitioner
A stylus which moves in conjunction with the control of the stimulus can mark field extend on pre-printed chart paper
What is the Friedmann VF analyser?
Presents 2,3 or 4 stimuli in VF
Patients report how many lights they saw
Light intensity can be altered using filters
Results are marked on a pre-printed sheet
What is a HVFA?
tests sensitivity for specific points in the peripheral visual field
px presses on the button when they see the stimulus
different colours, size and intensities are displayed
What is medmont automated perimetry?
similar to HVFA but on PC
how does retinal ganglion cell function related to visual field loss?
less redundancy, more noticealbe in MK cells
What is SWAP?
based on K cell pathway
decreased sensitivity to blue wavelength
more sensitive to glaucomatous changes
yellow-background- is used to de-sensitise the red and green cones
affected by older ppl- yellowing of lens
What is flicker perimetry?
based on M cell pathway
CFF- constant contrast
TMP- contrast is varied
What is FDT?
Sinusoidal grating of low spatial frequency undergoes rapid counterphase flicker at high temporal frequency
Stimulus appears to have twice the spatial frequency
removes low spatial frequencies
Patient must detect the presence of a ring – the core of the ring is brighter and the inner and outside edges darker
What is MERG?
records the electrical activity from 50-100 areas of the retina – electrodes either near the cornea or striate cortex
What are the 3 variations in stimulus size?
What is angular subtense?
a variation in stimulus size
relative size of the retina is the same for all testing distances
What is the physical size variation in stimuli?
relative size of retina will vary according to testing distance
What is the goldmann size?
size replicates that unsed in the goldmann bowl perimeter
Intensity vs sensitivity relationship?
greater the sensitivity of the eye, the lower the intensity of light for the threshold and the lower the stimulus intensity
In perimetry- how bright the background and stimulus appear
Stimulus and background intensity relationship?
intensities are measured in log scale - decibels
What is Bloch's law and how does it relate to the stimulus presentation time?
luminance x duration = constant
at a critical duration time, the brightness of the stimulus is proportional to the luminance and duration of the stimulus= temporal summation
What is the ideal stimulus presentation time?
: reduces temporal summation
: reaction time for the saccade of the eye to move to the periphery
What are 3 factors that affect the gradient of the seeing curve?
increase in px experience= steeper cruve and increased reliability
decreased sensitvity in the eye
: increased variability
What are screneing tests?
tests whether the points are seen 6dB brighter than threshold of HOV
What are the types of screening tests?
: all points either seen or not
: points that are missed are retested at max
: points missed retested for threshold value
What is a full threshold testing?
measured at 4 locations, each quadrant 9 deg away from fovea
2 reversal staircase
: 4dB reduced to 2dB when results become positive
threshold= dimmest light seen
What is FAST PAC?
: single step 3 dB
reduces testing time by 2/3rd
What is SITA?
Relies on prior knowledge
number of false positives
will adjust presentation rate according to px response rate
What is SITA standard?
What is SITA Fast?
3db single reservsal
What is the protocol 1 threshold test?
point grid falls on H + V axis
shit cos leaves 6 deg gap of test points at fixation
Why is protocol 2 preferred?
3 degree gap at macula- smaller
test on either side of midline
What are the HFVA tests that are available?
: 68 pt grid spaced 2 deg apart- macula+ advanced glaucoma
: 54 pt grid spaced 6 deg 30 deg nasally- glaucoma ONH
: 76 pt grid 6 deg spacing- glaucoma, retina, ONH
: 68 pt grid 30-60 deg- retinal changes, glaucoma
: 16 pt grid, 2 deg spacing, 5deg fovea
: 60 deg from fovea- glaucoma
What is the test selection choice for the retina periphery?
full field to 60 deg
What is the test selection for the macula?
central vision testing- 10, 24 or 32 deg
What is the test selection for glaucoma?
: 10-2 more central due to loss of peripheral
What are some of the human factors that affect testing?
: small, depressed
: older= dec retinal, cisual pathway, senile miosis
: increased performance= increased exp
increased sensitivity= dec variability
: dec retinal contrast
: difficulties in attention
: lids, spinal problem, prominent brow
What is the cutof for false positive results?
greater than 30%
What is the cutoff for false negative results?
greater than 30%
inattention/adfanvced field loss
What are sensitivity values?
compares measured sensitivity to age matched norms/HOV?
What is probaility plot?
sensitiviy at each point below norms/HOV?
What does a negative mean deriation mean?
loss in sensitivity
generall loss or smeall area of depression
What does a small/large pattern deviation mean?
: diffuse loss
: focal loss
MD- normal, PSD normal
MD- abnormal, PSD- normal?
generalised loss of sensitivity
MD normal, PSD abdnormal?
Small localised defect
MD abnormal, PSD abnormal?
large defects + localised component
averages resting of same point: varibility testing
Corrected pattern standard deviation?
index sensitive to focal loss
separates real deviation from theose due to variability
What is the glaucoma hemifield test?
decides if field loss is compatible with glaucoma diagnosis
What are considered abnormal results?
a point/cluster of points decreased in sensitivity that is repeatable
What is considered an abnormal result on the hymphrey?
glaucoma hemifield test norm- VF loss is compatible with glaucoma, PSD<5%
VF abnormal results?
single point p<0.5%
2 clustered points
: p<5%, one point p<1%
3 or more points
: p<5% + pattern of loss consistent with ocular pathlology
What is a sector scotoma?
damage to large bundle of fibres: field loss reflects pathway
What is a arculate scotoma?
damate to specific bundles of fibres
What is a centrocoeal scotoma
bilaterally due to tobacco/alcohol nutritional amblyopia
damage to papillomacular bundle
Damage to PRs?
irregular field loss of rod/cone dystrophy
e.g. retinitis pigmentosa
: damage to REP/PR- contricted fields
Damage to outer retina?
monocular- doent respect midline, rpe damage
What is a central scotoma?
damage at rpe, relative/absolute defect
What is a large monocular scotoma?
e.g. retinal detachment
damage doens't follow bundles of fibre and midline
What is a titled optic disc and how does it affect the visual field?
congenital defect, nasal bilateral
relative temporal defect
: doesnt respect vertical midline
: non- inflammatory swelling, ONHby increased intra cranial pressure- bilaterally enlarged blind spot
What is an optic nerve head drusen and how does it affect the visual field?
formed by accumulation of deposits- calcified mitochondria
: drusen pressures nerve fibre bundles
: specific bundles damaged
How does a tumour at the pituitary gland affect the visual field?
presses onto the optic chiasm
nasal fibres affected first, then all
How does haemorrhages and aneuryms at the circle of willis affect the visual field?
affects left of chiasm- LE temporal retinal fibres - affects nasal field
How do the fibres direct in the optic tract?
How does the LGN affect the visual field?
visual field defect increases in congruency, more posteriorly
Optic radiations and visual field?
pie in the sky
pie on the floor
increased in congruency, more posterior the fibres
V1 lesions visual field?
: congruent, more posterior
: slow progression
: physical damage can affect one or both hemispheres