Basics Of VF Interpretation Flashcards
When is perimetry utilized
Glaucoma
Neurological disease
Retinal disease
Role of perimetry in glaucoma
- fundamental in diagnosis and management
- perimetric test results that reproducibly demonstrate VF loss remain the most conclusive contributor to glaucoma diagnosis
- the most precise method for quantifying glaucomatous progression remains repeated VF testing
When do you use a SITA standard 30-2
Measures visual sensitivity at 76 locations within 30 degrees of fixation-the area commonly referred to as the central visual field
When do you use SITA standard 24-2
The 24-2 pattern tests 54 locations and is identical to the 30-2 pattern except that most of the outermost ring of potions has been removed
SITA-FAST 24-2
- the primary difference between the SITA standard and SITA fast strategies is the amount of certainty that is required before testing can be stopped
- overall effect usually is reduced testing time without loss f diagnostic information
SITA FAST 24-2 is less tolerant of what
Patient mistakes and may be best used in experienced or younger patients
Which is more difficult, SITA fast to SITA standard
SITA fasts presents stimuli that more often are just barely visible, and may be a more difficult test than SITA standard
-therefore SITA fast is not the preferred choice in patients expected to have difficulty with perimetric testing
SITA-standard 10-2
- covers only the area within 10 degrees of fixation using a grid of test points spaced every 2 degrees
- valuable when evaluating VF loss in macular disease
- late stage glaucoma
- SITA FAST 10-2
Testing for drug induced maculopathy
Good for hydroxychloroquine using patients
10-2
Disability testing and VF
Some people want to be on disability, or for driving
Retinal disease and 24-2
VF testing has a role in the diagnosis and management of some retinal disease,s but direct observation and imaging of the fundus usually are of a greater values
-perimetry then becomes one of many ancillary tests
What kind of testing for visibility
Suprathreshold
A test is which the only goal is to confirm that visual function is not below the normal range
Suprathreshold testing
- does not provide quantitative data
- are not as sensitive to early field loss as threshold tests
Selecting a test for VF
-threshold testing is always a good choice, and in sopthalmic clinical settings, it is almost always to be preferred over suprathreshold screening tests
Standard of care for patients that’s have established field loss
Threshold testing
Most common VF test used
24-2
Normal time for SIAT fast
2-5 minutes
Time for standard Sita 24-2
5-7 minutes
Why switch to a 10-2 for late stage glaucoma
Peripheral vision is already gone, not sense in going through the whole thing
VF for macular disease
10-2
Perimetric follow up
It is usually best to follow a patient over time using the same test that was used for diagnosis
Why do we need to use the same test every time we test a patient
If a patient is consistently examined with the same test strategy and test pattern, then tests can be more easily compared using standardized progression analyses
Measures the tendency of patients to press the response button even when no stimulus has actually been seen
False positive
Trigger happy
False positive
Most important and used of the three available reliability indices
False positives
Assess patient inattention
False negative errors
Help identify patients who have failed to persons to stimuli that probably should have been seen
False negative
Measures patient gaze stability, whether the patient is gazing straight ahead or looking from side to side during the test
Fixation losses
An automatic dual-variable gaze tracker
Measures gaze direction every time a stimulus is presented
False negatives in glaucoma
Can be high in glaucoma even if they are paying attention
On the gaze tracking record, lines extending upward
Indicates the amount of gaze error during each stimulus presentation, with full scale indicating gaze errors of 10 degrees
On the gaze tracking record, lines extending downward
Indicate that’s the instrument was unsuccessful in measuring gaze direction during that particular stimulus presentation, for instance, because of a blink
This presentation simply shows the measured decibel sensitivity at each tested point, and is the basic information upon which all the analyses and printouts are based
Numerical threshold sensitivities
These highlight loss after first correcting for any overall change in the height of the hill of vision, such as that caused by cataract
Pattern deviation maps
Single most useful STATPAC analysis when glaucoma is suspected
The pattern deviation probability plot
Comparing total deviation and pattern deviation
If the two maps look more or less the same, then there is little or no generalized depression
-on the other hand, a uniformly depressed total deviation map combined with a normal-looking pattern deviation map probability infdicates a cataract
A pattern deviation map that looks more disrupted than its corresponding total deviation map
Often associated with a trigger happy patient who has repeatedly pressed the response button when no stimulus was seen
Mean deviation
Weighted average of the values eprestned in the total deviation numerical plot, with 0 indicating no deviation from normal and larger negative values being associated with advanced field loss
When is MD primary used for
Stage VF loss and as a metric for rate of change over time
-approximately 0 dB in normal and -30dB to -35 dB in extreme filed loss
Visual field index
An enhancement of MD that is designed to be less affected by cataract and more sensitive to changes near the center of the field, in order to better correlate with ganglion cells loss
Normal vision is associated with VFI clauses near _____
100%
Pattern standard deviation (PSD) summarizes
Localized loss in a single index, which ignoring generalized depression
-low in normal fields, for uniformly depressed fields and for blind fields, and is highest in moderate to advanced localized loss
Expert system for analyzing threshold test results
The glaucoma hemifield test
-it has been reported to detect glaucomatous VF loss with both high sensitivity and high specificity and expresses its analysis in plain language
The single best place to look for practitioners who are not highly experienced at visual field analysis
Glaucoma hemifield test
The GHT was not designed for what
Toe be sensitive to neurological or retinal field loss
