Threshold Packet 1&2, MT1 Material Flashcards
humphrey field analyzer (HFA 24-2) has how many test points?
54
HFA 30-2 has how many test points?
76
Octopus G test has how many test poins?
59
quantitative perimetry CPT code is:
92083
what is an important trend of fluctuation
fluctuation (fatigue, boredom, attention) can increase in the earliest stages of VF loss that will later become definite VF defects
if VF loss is getting deeper is it a higher or lower dB value
lower dB value
what should have the highest sensitivity in the VF?
fovea
how much does the perifoveal sensitivity drop off?
drops 2-4 dB at the first ring of points outside of the fovea
what is defined as central VF? how does sensitivity drop off?
central 30 degrees radius around fixation
-sensitivity declines about 3dB/10 degrees (more rapid decline in superior VF beyond 15/20 degrees)
type of fluctuation that occurs during a threshold test, impacts whether there appears to be a VF defect or not
short-term fluctuation (STF)
type of fluctuation that is typically about 2dB on average across all points in the VF
short-term fluctuation (STF)
type of fluctuation that increases with the distance from fixation
short-term fluctuation (STF)
-significantly greater in the peripheral VF and superiorly beyond 15/20 degrees
type of fluctuation that is between threshold tests
long term fluctuation
type of fluctuation that impacts whether the VF or VF defect appears to be changing/progressing or stable
long term fluctuation
what type of perimetry is a “white stimulus on a white background” like HFA, Octopus, and several other instruments
standard automated perimetry (SAP)
what type of perimetry has less variability/fluctuation, therefore you can recognize true VF loss more confidently and can recognize true progression/change more confidently
standard automated perimetry (SAP)
what type of perimetry is most commonly used type of perimetry for following glaucoma
standard automated perimetry (SAP)
what is alternative perimetry
uses a stimulus other than a white stimulus white background, usually one that stimulates a small subset of retinal ganglion cells (m-cells)
SWAP=
short wavelength automated perimetry
-blue stimulus on yellow background
pros/cons of alternative perimetry
- designed to detect VF loss earlier than SAP but tends to have more variability/fluctuation
- increased fluctuation/variability
why use SAP rather than alternative perimetry?
- less variability/fluctuation
- best progressive software to detect change/progression
- most sensitive to early glaucomatous VF loss than white-on-white screening VF
false field defects are very common in threshold perimetry, and the specificity is not good, at best ___- ___%
60-70 %
explain why interpretation is often much more difficult in threshold vs. screening
because you are interpreting dB value sensitivities (not misses vs. hits) and this causes reduced specificity
indications for threshold perimetry
- central VF defect that may change with tim e
- glaucoma suspects
- glaucoma patients
- macular disease
- neuro-ophthalmic disorders
the small pupil effect can cause what on the VF?
generalized depression
more likely if cataract is present as well
most common causes of no BS:
- neither eye is patched
- wrong eye is patched
- poor fixation and perimetrist is not monitoring
do you need trial lenses for the octopus VF on QTC patients?
no lenses needed
-lenses are not needed for peripheral VF
if patient is dilated, what trial lens do you use
assume patient is completely cyclopleged so we give +3.25 add (over distance Rx)
if the lensholder is much too far from the eye, what will it cause?
a major lens/lensholder artifact at 10 or 15 degrees from fixation
the most common artifact from lensholder is
temporal to blindspot
which is extremely unlikely location for early glaucomatous VF loss
why is having the foveal threshold response on good?
it helps the perimetrist to recognize FP responses during the test and to prevent it
patient ed on gaze tracker is:
look in the middle at the orange/yellow light. blink your eyes 3 or 4 times and now hold your eyes wide open and don’t blink or move your eyes
sensitivities higher than the fovea suggest:
false positive responses
what is a true fixation loss
patient not looking at the central (orange) light, preterits should be able to see this
what causes poor BS localization?
very often due to false positive responses or false negatives as the instrument tries to localize the BS at the beginning go the test
central field test point pattern is:
6 degree grid pattern with points straddling the midline
why do we use SITA strategies?
faster, less variability/fluctuation, more reliable, more repeatable results
-can more confidently recognize VF loss and progression of VF loss
when evaluating the reliability of the results, you look at what indices?
- fixation losses
- false positive trials
- false negative trials
- fixation losses
significance of FP responses?
- can cause a VF defect to be missed
- VFI and MD will likely be higher than they should be
- can destroy the reliability of the test
what % of FP is flagged on HFA printout?
33
what are some clues to FP responses during the test
- sensitivity values that are higher than expected
- fixation loss index shows several fixation losses but the patient’s fixation was very steady on the video eye monitor
causes of false negative responses
- large or deep VF loss
- can be due to fatigue, lack of attention
do high FNs always indicate reduced test reliability?
they do not necessarily indicate reduced test reliability, they very often indicate much VF loss such as in advanced glaucoma
what are some ways to detect increased FNs?
- increased FN index (>33%)
- can be due to fatigue, lack of attention
- several seconds of no responses during the test, usually late in test
- slow or late responses
why should you not use greytone alone to interpret the VF?
- lower sensitivities are colored darker therefore more peripheral areas will normally be darker
- not adjusted for age, on an absolute scale
- can miss VF defects
what does the “numeric total deviation map” represent?
the difference between the pt’s sensitivities of pts in the normal database of the same age
what does a minus number on the numeric total deviation map represent?
lower than “normal” sensitivities, possible VF loss
what does a plus number on the numeric total deviation map represent?
higher than normal sensitivities due to a pt’s sensitivities being higher than the average. can be caused by FP response or wrong birthdate entered
what is done to pattern deviation maps to minimize the chance that localized defects hide within deep generalized depression?
plots are “corrected” for any generalized loss of sensitivity or generalized higher than normal sensitivity
common causes of generalized depression
- blur (wrong trial lens)
- small pupil (< 3mm)
- media opacity (cataract)
- fatigue
- 1st threshold VF test
- glaucoma (but often hard to isolate as the cause)
what does it mean if the total and pattern deviation maps look very similar
there is little or no generalized depression
what does it mean if there are:
- many significantly depressed points on the total deviation maps
- none or very few depressed points on the pattern deviation maps
generalized depression, often cataract
what does it mean is there are:
- many significantly depressed points on the pattern deviation maps
- none or very few depressed points on the total deviation maps
probably “trigger happy” patient who gave many FP responses
the cause of localized VF loss should almost always be evident in the eye if the loss is:
anterior to the lateral geniculate
GHT=
glaucoma hemifield test
what is the GHT?
an analysis of HFA 30-2 or 24-2 results which compares groups of test points in the superior hemifield to the mirror image groups in the inferior hemifield
what is important about the groups tested in the GHT?
the groups follow the pathway of the arcuate nerve fiber bundles which are very often damaged in early glaucoma
GHT is very useful for identifying:
glaucomatous VF loss
what does GHT not give you though?
does not give info on the location or pattern of the VF defect(s)
what are the 2 global indices
MD= mean deviation on HFA PSD= pattern standard deviation
what is the mean deviation indices (MD)
the difference in average sensitivity of the patient and same-age normal patient in the normal/reference database
MD is most affected by what two factors:
- number of defective points (size of VF defect)
- depth of VF loss at defective points
what type of defects most increase MD?
large, deep VF defects most increase MD (in minus direction)
what is PSD?
index of localized irregularity of the surface of the patient’s hill of vision
what type of defects most increase PSD?
most by deep, localized VF defects
as VF ____ in size, the PSD starts decreasing
increase
increased MD and normal PSD=
probable gen depression
increased MD and increased PSD=
probable large and/or very deep localized defects
normal MD and increased PSD=
localized VF defects
