Visual Fields Flashcards
what are the two types of perimetry?
-kinetic
-static
what are the two types of kinetic perimetry?
-Goldmann
-Octopus
-gross (simple version)
what is recorded as the threshold in kinetic perimetry?
the specific location where the stimulus is just seen
what is kinetic perimetry?
perimetry where the size and luminance of the target can be varied
what do the rings and lines on a kinetic perimetry diagram show?
rings show extent of the visual field
lines are what the px reports they can actually see
why do you need to make sure the stimulus brightness in kinetic perimetry is just right?
because a big bright target could mean px subtle defects are missed and targets too small/ dim just wont be picked up regardless of wether the px has a defect
what are the advantages of kinetic perimetry?
-not confined to testing algorithms
-useful for patients with motility issues
why would you choose static over kinetic perimetry?
-as you need an experienced practitioner to do static compared to kinetic where it can be delegated
-you can see moving targets in the periphery better than stationary targets in the periphery
-it is reaction time dependent
what is static perimetry?
perimetry where light stimuli are presented at fixed locations
what are the two types of static perimetry
-suprathreshold
-threshold
what does C40 on suprathreshold perimetry mean?
central and 40 is the number of points presented to the patient
how is the brightness of the light of stimulus used in suprathreshold perimetry decided?
its 8dB brighter than the lowest amount of brightness the px is expected to see for their age
in suprathreshold, how does the brightness of the stimulus change?
as the stimulus moves into the periphery, the dimmer it gets
what are the advantages to suprathreshold?
-good for screening
-quick
-patients are expected to have normal visual fields
-good for patients at risk of a gross field defect
what are the disadvantages of suprathreshold perimetry>?
-miss subtle defects
-not useful in glaucoma suspects
-inconclusive defects on suprathreshold tests
what are the two types of suprathreshold perimetry?
c40 and ff81
what is the main difference between c40 and ff81 types of suprathreshold perimetry?
Main difference is c40 covers 30 degrees either side of fixation whereas ff81 covers 60 degrees either side so a larger field of visual fixation. C40 really should only be used for suspected macular problems or for a quick screening test
what is standard colour and size for static perimetry?
standard colour white
standard size 3
what is the threshold of the stimulus in threshold perimetry?
the minimum amount of light that gives a 50% detection probability
when may you make the size of stimulus bigger in threshold perimetry?
if the patient has poorer vision
what algorithm is most commonly used in threshold perimetry and why?
Full Threshold algorithm as its the gold standard by being the most accurate algorithm using a 4-2db staircase method
for threshold perimetry, what test pattern is used as standard? what test pattern is good for macula testing?
-central 24-2 = good for glaucoma, general and neurological pathologies
-central 10-2
what is esterman?
a suprathreshold test that the patient does binocularly
how do you use visual fields on a patient to test if they are fit to drive under DVLA?
-do Esterman
-make sure there is no rim artefacts if they wear their glasses
-they are allowed three attempts in their visit
-send it to DVLA if 3 attempts later and still not up to driving standards
-you can’s discuss with the px their test results
on esterman what is the highest percentage of false positive score?
no more than 20%
how does sita work?
uses a staircase method while constructing mathematical models of normal and abnormal visual behaviour by comparing the frequency of seeing curve of the normal eye to the patients eye
what are the three types of sita? which is most common?
Most patients do sita fast but others are sita standard and sita faster but the longer the test goes on for, the more accurate the result so if you can do standard,
how does sita reduce test time?
continuously updates the algorithm based on patient responses including altering stimuli presentation and speed based on reaction time
What are the positives of threshold testing?
-detects subtle defects including early glaucoma
-gives us info on the depth (severity) of the defect
-better comparison of results to age matched normative data
-visual field is mapped with more precision
-can be used to closely monitor the progression of visual field loss in detail
what are the minimum visual fields to meet driving standard?
-group 1: field of at least 120 degrees on the horizontal using a target equivalent to white Goldman iii4e. No significant defect in the binocular field within 20 degrees of fixation above or below the horizontal meridian
-group 2: horizontal visual field of at least 160 degrees, extension should be at least 70 degrees left and right and 30 degrees up and down . no defects should be present within central 30 degree radius
what is the extent of the visual field nasally?
60 degrees
where is the blindspot located in a healthy patient with full VFs?
15 degrees horizontally and 1.5 degrees below fixation
how do images on the retina compare to on the VF?
Images are upside down and inverted on the retina so:
- if there’s a visual defect superiorly on the retina then it will affect the inferior visual field
-Blind spot is on the temporal field as the optic disc is on the nasal retina
check google docs OP2501 term 1 to see how the hill of vision looks depending on the field loss
ok
what does diffuse field loss look like compared to normal field loss?
just depression of the whole visual field
what does contraction of the visual field suggest?
the patient has tunnel vision
give 4 hills of vision depending on the VF
-normal
-diffuse VF loss
-focal VF loss
-visual field contraction
in VF defects what does it mean when:
the vertical midline is crossed?
the vertical midline is respected?
-loss is retinal or optic disk related
-loss is to do with the brain (more serious)
check ss to see the different types of VF losses
ok
what are the names of the common glaucomatous patterns of loss?
-nasal step
-paracentral
-temporal wedge
-altudinal
-arcuate
-advanced
What does a “Nasal Step” defect indicate in a visual field test?
A Nasal Step defect is characterized by loss of sensitivity along the nasal side of the visual field, often indicative of early glaucoma.
How does a Paracentral defect appear on a visual field test?
A Paracentral defect involves localized loss of sensitivity near the central vision, often associated with glaucoma.
What is a Temporal Wedge defect in visual field testing?
A Temporal Wedge defect appears as a wedge-shaped area of sensitivity loss on the temporal side, which can be due to nerve fiber layer damage.
What is an Altitudinal defect, and what causes it?
An Altitudinal defect refers to a loss of vision in the upper or lower half of the visual field, often caused by ischemic optic neuropathy.
Describe an Arcuate defect in visual field testing.
An Arcuate defect is an arc-shaped area of vision loss extending from the blind spot, typical in glaucoma due to nerve fiber damage.
What does an Advanced visual field defect indicate?
Advanced defects show widespread sensitivity loss across most of the visual field, often found in late-stage glaucoma or severe optic nerve damage.
What is the result of a lesion in the right optic nerve?
A lesion in the right optic nerve causes complete vision loss in the right eye.
What visual field defect results from damage to the optic chiasm?
A lesion at the optic chiasm causes bitemporal hemianopia, characterized by loss of peripheral vision in both eyes.
What happens with a lesion in the right optic tract?
A lesion in the right optic tract results in left homonymous hemianopia, where the left visual field is lost in both eyes.
How does damage to the right occipital lobe (upper bank) affect vision?
A lesion in the right occipital lobe’s upper bank causes left inferior quadrantanopia, with loss of the lower-left quadrant in both eyes.
What defect arises from a lesion in the right occipital lobe (lower bank)?
A lesion in the right occipital lobe’s lower bank leads to left superior quadrantanopia, with loss of the upper-left quadrant in both eyes.
What is the effect of a large lesion in the right occipital lobe?
A large lesion in the right occipital lobe causes left homonymous hemianopia, sparing the macula.
A large lesion in the right occipital lobe causes left homonymous hemianopia, sparing the macula.
A lesion at the tip of the right occipital lobe results in macular-sparing left homonymous hemianopia, with central vision preserved.
what does homonymous mean in VFs?
same side of VF is affected in both eyes
what is a heteronymous VF defect?
occurs on opposite side of the field is affected in the two eyes
what does congruence of a defect mean?
how much the hemianopias in the right eye and left eye resemble each other
what else should you consider when evaluating VF results?
History
Symptoms
General health
Examination results
when evaluating history with VFs, what should you think about?
-family history so RP or glaucoma
-previous eye problems like optic neuropathy or retinal detachment
when evaluating previous eye problems with VFs, what ones should you think about?
-optic neuropathy?
-retinal detachment?
when evaluating general health with VFs, what should you think about?
-diabetes
-high blood pressure could mean vein or
artery occlusion
-rheumatoid arthritis could mean when evaluating history with VFs, what should you think about?
-benign intracranial hypertension- papilledema in the disk
when evaluating eye examination with VFs, what should you do?
-check VA
-check VB
-colour vision: colour vision problems from optic neuritis
-Slit lamp - cataract?
-Volk - disk looking suspicious of glaucoma? Retinal haemorrhages? Cotton wool spots?
what is the altitudinal defect?
loss of vision in either the upper or lower half of the visual field, typically divided along the horizontal midline.
What could the altitudinal defect cause?
Anterior Ischaemic Optic Neuropathy (AION)
Branch retinal vein occlusion
Retinal detachment
what could tunnel vision indicate?
- Retinitis pigmentosa
- Advanced glaucoma
- Central retinal vein occlusion
- Stroke
what could an enlarged blind spot mean?
-papilledema
-optic neuritis if just in one eye
check slide 18 on CV2 and learn it
ok
what could centrocecal scotoma mean?
toxic optic neuropathy
what is binasal hemianopia?
very rare-linked to carotid artery aneurysm
what does spiral visual fields mean?
-patient isnt good at test
-migraine
-functional visual loss = mainly (px is making it up)
what does a left central scotoma indicate?
central macular disease
why does central vein occlusion cause tunnel vision?
because it affects the whole of the retina so both upper and lower parts
what are the two types of quadrantanopia?
Meyers loop – temporal lobe
– pie in the sky
Optic radiations – parietal
lobe – pie on the floor
what could quadrantanopia mean?
tumour or trauma to the brain
when is a VF test poor reliability?
If there us 20% or more false negatives or blindspot errors meaning the test needs to be repeated
if you find a VF defect what’s the first thing you should do in terms of confirmation?
you should repeat it as the learning effect will be included in the second repeat and if the defect goes away, you know it’s not an actual defect. Repeats should take place on the same day unless you feel it was a struggle for the PX like they took a long time you may do it another day as you don’t want to fatigue the VF as that may cause performance to be reduced
how should you review a VF that has a defect for sure?
-Once the Px has repeatable VF loss, they need to be referred. Glaucoma suspect needs a band 2 appt where they are dilated and re checked
-Pattern of loss that respects the vertical midline, could me more serious so emergency - call the hospital asap for referral
-Significant unexplained loss needs referral
what is a false positive in SITA?
calculation of the response rate of the last 10 stimuli and if they are responding faster than that response rate then you know its a false positive
know what areas of a VF result mean Px is most likely getting false negative results
check google docs term 1 page 28
what does a positive mean deviation value mean?
patients are getting high false positives
what is the normal mean deviation range?
0 to -2sB.
name 2 types of artefact
a ptosis artefact and a trial lens artefact
what is the pattern deviation good for?
monitoring glaucoma as it highlights subtle loss compared to total deviation map which gives you a general overview.
what is total deviation made up of?
diffuse + localised
what does it mean if the whole hill of vision is depressed?
there is a total deviation loss or a negative deviation value
what % should fixation loss be less than?
less than 10%
what are the measures of fixation reliability in automated visual fields?
-false positives
-false negatives
-fixation losses
when do false positives occur?
trigger happy patient, pressed the button when no stimulus is presented and instead press to the sound of the actual machine instead of the light
what is and what causes false negatives?
when a patient could not see a bright stimulus in the same spot they previously saw a dim stimulus. These can occur because the patient is not paying attention or is becoming fatigued with the test
what are fixation losses on visual fields?
where the machine calculates where the blindspot by shining a light in this area and if the patient responds they are not focussing correctly
what can high false negatives suggest?
the patient does have a visual defect
what does a cloverleaf pattern on a visual field map suggest?
the patient has poor visual attention = false negative response
what 11 things can you look at that help you analyse a visual field plot?
-reliability indices
-threshold values
-greyscale map
-numerical total deviation map
-total deviation probability map
-numerical pattern deviation map’
-pattern deviation probability map
-glaucoma hemifield test
-visual field indices
-probability symbols
-gaze tracking
how does a greyscale map work?
where absolute values
of threshold converted to
grayscale for a quick
overview of fields
As depth of defect
increases (more severe
loss) grey becomes darker
why cant you solely rely on a grayscale map?
as it can be misleading as data is not compared to normal ranges meaning you can miss subtle defects
compare and contrast total deviation with pattern deviation
-total deviation map shows the deviation from age corrected
normal in numerical dB whereas pattern deviation highlights localised loss after correcting for a general depression in the hill of vision
compare total deviation probability map with pattern deviation probability map
Total deviation probability map highlights how likely this is to fall outside of normal – as indicated by the probability symbols while pattern deviation probability map highlights the statistical significance of numerical values
what do the probability symbols mean?
the darker the square, the less likely it is to be normal
what does the glaucoma hemifield test do?
compares pattern deviation scores in 5 zones of upper hemifield to mirror image zones in lower hemifield and differences between hemifields are compared to normative data
what on GHT is a high indication of glaucoma?
when you get a repeatable message of ‘outside normal limits’
What is the Visual Field Index (VFI)?
The Visual Field Index (VFI) is a summary measure of visual field function, expressed as a percentage, where 100% indicates a normal visual field and 0% indicates complete blindness
How is the VFI less affected by cataracts?
The VFI gives greater weight to central vision and minimizes the impact of cataracts by focusing on ganglion cell function rather than diffuse field depression caused by lens opacities.
What is the relationship between VFI and ganglion cell loss?
The VFI shows improved correspondence to ganglion cell loss, making it a more accurate measure of glaucomatous damage compared to older indices like Mean Deviation (MD).
what is the mean deviation (MD)?
it’s the weighted mean of the total deviation where 0dB is normal and the worse the field the more negative the value
what is pattern standard deviation?
The difference between the total deviation plots, where focal loss increases as the value becomes more positive and it goes up to 12dB and after this the loss becomes more diffuse
what does a value of 1dB mean in terms of pattern standard deviation?
the difference between the total deviation plots is the same
