VF Testing Flashcards
Testing strategies
- automated perimeter
- manual perimeters (tangent screen, Goldman bowl perimeter)
- CVF
The systemic measurement of visual function
Perimetry
The measurement of hill of vision in terms of establishing the patients differential light sensitivity across the VF
Perimetery
Threshold
Location at which detecting threshold is determined
How are sensitivity and threshold related
Inversely
Standard Humphrey VF: kinetic or static?
Static
-present different targets, but they are not moving targets
Tangent screen: kinetic or static?
Kinetic
- physically moving the target
0dB sensitivity
Very low
Typically range of abnormal vision
0-30dB
Normal peripheral sensitivity range
20-40dB
Limit of fovea vision
40dB
Defined as that area of vision seen with open eyes
Visual field
Dimensions of the visual field defined
Defined relative to fixation
Basis of VF
Present of pR and corresponding visual pathways up to the periphery or retina away from point of fixation (fovea)
Importance of VF
Reflects topographic sensitivity of various foci on retina and corresponding visual apparatus
How should you look at VF
OD on the right and OS on the left so you can see differnt heminaopsia correctly
Status perimetry
- computer presents stimuli in a random fashion
- speed is also improved with random presentation
- allows for storage of data
- computer assisted stat analysis is available
- most widely used intros meant is the Humphrey VF
- testing methods and stat analysis vary among manufacturers
- static auto perimetry measures retinal sensitivity at predetermined points throughout the VF
- threshold values are determined to discover the shape of the hill of vision
How does static perimetry measure threshold
Stimulus at a stationary position is presented by increasing or decreasing the luminance until just noticed by the patients
HFA-3
- newest one
- bowl/projection
- optical system
- central processor
- patient interface
What is special about the HFA-3
-liquid lens technology allows you to automatically load each pateitns refractive correction form the previous exam
SITA faster
About half the time of SITA standard and 70% of SITA fast with the same reproducibility as SITA fast
-may improve patient satisfaction with perimetric testing and reduce patient fatigue
What kind of add do you use for presbyopia in HFA-2
3.33
Working distance is 30cm not 40 so cannot use 2.50 as a max
HVF: bowl
- aspherical surface where stimuli are projected
- distance from the eye to the center of the bowl is 30cm
- this value dictates the warranted corrective lens wchi should be used dudeitn testing
Optical system in HVF
Provides stimuli of known brightness for a known amount of time in aprecise location against a background of known background
HVF background lumincation
- 5asb
- dimmer background allow a machine to Preston brighter stimulu to the visua lsystem with respect to background light
HVF: stimulus size
- utilizes the same target size as a Goldman perimeter: I, II, III, IV, V
- all size III targets is most often used during testing, however size V stimulus is used on occasions
Diamter of the III size in HVF
2.26mm
Stimulus intensity of HVF
- 0.08asb (51db)-10,000 (0dB)
- brightest target is equivalent to goldmann V4e
- does not switch between target sizes (changes brightness of target only)
Stimulus duration of HVF
- around 0.2s
- patient does not have time to see a stimulus in their periphery and look towards
Brightest setting on golamdnn
V4e
10,000asb
Fixation monitoring in HVF
Includes examiner ability to view the patients eye, an electronic eye motion detector (gaze tracker) and blind spot monitoring
Blind spot monitoring
Provides an index of the quality of fixation by presenting a stimuli in the blind spot-positive responses indicate poor fixation
Gaze tracker
- measure gaze direction with precision of approx one degree
- these tracking results are shown on the video screen and are printed at the bottom of the print out
Calibration of HVF
-done automatically by the instrumentcalibration of background and target
Room luminance and HVF
Should be dark without visual or auditory distractions
Data entry of HVF
- always enter the date, time, patients name, identification or chart number,and BD
- can also add VA, pupil diameters, and refractive error
HVF pateitn set up
- always disinfect surfaces
- one eye is occluded
- chin holder adjusted until the pateitns virwing eye is centered in crosshairs on the screen
- lens holder containing appropriate near spectacle ass is placed as close to the patients eye as possible without touching the lashes
Considerations for HVF
- anyone who is aphakic
- anyone who is pseudophakic
- anyone that has been dilated
Is it better to be dilated or miotic for VF
Dilated is better, but dont want to be either really
Trial lens placement for HVF
- rimless trial frame
- if Plano, put the lens holder down
- ensure the trial lens is as close as possible to the patient without touching the patients lashes
- if performing peripheral VF (outside the central 30), you must remove the trial lens
Patients instructions for HVA3
- instructions are extremely impiortnat
- if not given properly, will affect test results
- show the patient the button press and how to operate
- patient should be shown the yellow fixation light in the center of he HVF and instructed to look at it throughout the entire test-must NOT look away
- explain that while the fixate on the central light, the computer will flash small spots of light in their side vision
- they are not to look at the side lights-keep looking straight ahead
- press the button each time they believe they views light off to the side )even if they only thin they’ve seen it)
- ok to blink when needed
HVF during the test
- watch for fixation losses
- do not leave the room
- reposition pateitn slightly if necessary during the test
- perform test on other eye
- always save and print results
HVF: procedures
- examination strategy
- screening
- standard algorithm (full threshold)
- FASTPAC
- SITA
Screening HVF
- single intensity
- threshold related
- three zone
Standard algorithm (full trehshold )
- full threshold
- full threshold from prior data
- fast threshold
Screening on HVF
- not quantitative
- save time
- reserved for new patients where the suspicions of a defect is low
- if defects are found, examination using a threshold test hsould be performed and used to monitor disease
Single intensity on HVF
One value of brightness is presented at all points being tests
-default is 24Db
Threshold related: HVF screening
Makes the screening target threshold the same across the entire filed
-me Audrey a central threshold and a peripheral threshold and then creates a normal hill of vision from the two values
Three zone: HVA
Takes threshold a step further
-if the suprakthreshold target is missed that spot is retested later with a maximum intensity target of 0DB (10,000 abs)
three zone results:
- normal (Sade suprathershold)
- relative defect (missed Supra, but Saw max)
- abolsute defect )did not see max)
Full threshold
Most time sounding, however most accurate and repdoruducle
- threshold is detemeind for one primary point per quadrant. 9 degrees away from horizontal and vertical (30-2)
- this is then used to determine starting point for the staircase at other locations thrghouout the fiel
- these trehshlds then feed into the staircase onset of their neighbors
Staircase of full threshold
- consists of 4dB decrement in light intently until the patient fails to repsosne=1st reversal
- then 2Db increments uintl the pateitns faisl to see the light again=2nd reversal. This level is the sensitivity printed
- primary points habe threshold estimated twice
If any threshold value deviated by >5dB from expected, then it
Brackets the thriesld once’s more
)parenthesis if more accurate than bracket)
FASTPAC
- alternative to full threshold
- changes stimulus instensity by 3db and only crosses the threshold once
- can reduce test trim by as much as 35% however, this comes at an expense to accuracy
- less precise
SITA
- uses method of detecting threshold values for 4 ptimayt point in each quadrant
- these are used to generate starting levels of neighboring points
- the result is that threshold determination is reached in a shorter amount of time but with the same accuracy as a fullthreshold
- monitor test point results and utilizes a complex stat technique which assigns a level of confidence for how close each point it to its final value
SITA standard vs SITA fast
- main difference is the level of confidence. Standard is more reproducibly
- standard sets a higher level of certainty which requires more trials at a give point this its more accurate
- SITA fast takes less time
Which is good for glaucoma tracking
24-2 or 30-1
Central 30
-76 test point locations that’s covers the central 30 degrees
Spaced 6 degrees apart
Central 24
- 54 test point locations
- covers the central 24 degrees, except nasally where it extends 30 degrees
- space locations 6 degrees apart
- can pick up a nasal step in glaucoma where early glaucoma damage starts
- still covers 30 degrees at the nasal margin
Central 10
68 test point locations
Spaced 2 degrees apart (instead of 6)
Version 1 HVF
- spaces locations 6 degrees apart
- places testing locations on the horizontal and vertical meridians
Version -2 of HVF
- spaces locations 6 degrees apart
- places testing locations flanking the horizontal and vertical meridians
Almost never use -1. -2 is the most used
Periphal zone
- mapping of the field between 30 and 60 degrees (30/60-1, 30/60-2, 60-4, current test on HFA3)
- meant to supplement a central field exam when a more extensive dield defect is suspected
- seldom used, such defects better evaluated with Goldman
Full field
- threshold strategies not available for full field programs
- takes too long to acpcmplosh
- divert to goldmann
SWAP
Designed for early detection of glaucoma based on the theroty that glaucoma selectively damages door wavelgnth fibers first
- also known as BY perimetry
- 31.5asb background with a yellow background of 100-200
- blue filter is placed int he stimulus projection pathway
- sive V is used
- stimulus duration of 0.2 seconds remain constant
Indications of HVF
- suspected VF defect
- retinal disease (RP)
- neuro ophthalmic disease
- glaucoma
Quantitivative tsting
- purely quantitative
- performed in order to quantify a suspected VF
- performed in order to establish baseline fueled against which future fields may be compared
- high sensitivity
Advantages of VF
- testing administration is more satnadardizable
- minimizes test variability
- improves reliability
Disadvantages of HVF
- expensive
- very tedious for certain Patietns=fatigue
- requires a strong knowledge of data interpretation by the examiner
Types of screeening
- FDP (frequency doubling perimetry)
- fast trehshold estimation strategy
- HVF screening tests
Zeus’s FDT
Includes realizability indices
- fixation losses: 6 trials for threshold mode and 3 trials for screening mode
- both are flagged at 33%
- false positive in both testing modes
- false negatives only in threshold mode
Zeus’s FDT: patterns
Suprathreshold C-20 and C-30 screening
C-20-5 full trehshold
-tests the central 20 degrees at 17 locations
N-30-5 full threshold
-tests all the points of C-20 tests, plus two additional nasal locations for a total of 19 locations
Advantages for automated perimetry: screening
- portable and compact
- affordable
- no trial lens or eye patch
- high level of sensitivity of specificity
- rapid assessment of the field
- reduced learning curves
Disadvantage of automated perimetry: screening
- results limited by cataract and pupils <3mm
- trouble detecting small scotomas due to the fact that the FDT uses larger test targets
- offers fewer testing points (17 or 19) vs a HVF
Clover leaf pattern
Tired
