Test 3 Flashcards
The ON causes a physiologic blind spot where
15 degrees temporal
Along horizontal meridian 40% above, 60% below. Vertically oval.
7 degrees high, 5 degrees wide.
Absolute scotoma
Limit of foveal vision
Normal peripheral sensitivity range
Typical range of abnormal vision
40 dB
20-40dB
0-30 dB
As dB increases, brightness decreases.
Brightest stimulus in dB and abs
Brightest = 0 dB, 10,000 abs
Dimmest= 50dB, 0.1 Abs
How is the size of the stimulus defined
Defined as the target size and distance from eye.
1mm target at 33 cm distance
Traditional unit of light for perimetry- standard background luminance
31.5abs
Most common stimulus size
0.43 degrees (Goldman size III)
temporal summation ensures linear relationship between
Stimulus duration and threshold.
Stimulus duration doubles = threshold doubles.
Max duration - 500msec
Most frequent used duration - 200msec (prevents tendency for re-fixation and gives pt time to respond)
Kinetic perimetry speed
3 to 5 degrees per second. (4)
too slow- encourages refixation
too fast- Isopter becomes artificially small.
When is contrast sensitivity used for the stimulus?
Sine wave gratings to increase the sensitivity of peripheral defects.
Temporal contrast. Flickering.
About __% of normal first time testers have abnormal results
15%
Pupil size that is too small and reduces retinal luminance
2.5mm. May need to dilate. Large pupils may reduce sensitivity in central target locations.
Lack of correction reduces sensitivity by ___dB per diopter of blur using goldman size 3 target
1 dB per 1 D
Astigmatism should be corrected when it is more than
1.50DC
Age reduces visual acuity __dB per decade
1dB per 1 decade
Relative scotoma
Big target/easy to see =
Small target/hard to see =
Big target= small defect
small target= big defect
Manual perimetry tests and if they can do static or kinetic testing or both
- Tangent screen- kinetic, static
- Arc perimeter, kinetic only
- Goldman Perimeter- kinetic, standard
Advantages and disadvantages to tangent screen
Low cost, simple to operate
Hard to reproduce results, room lighting is variable, does not assess peripheral field.
Tangent screen Tests ___ central degrees in the visual field
What two techniques can be performed?
30
Kinetic and supratrheshold
results with a hysterical patient (conversion disorder)
Tubular field
Psychological, not pathological.
Move patient back from 1m to 2m, VF results stay the same.
Arc perimeter measures what how far in the periphery? Target sizes (2) how many meridians tested? Testing distance?
Both central and peripheral fields. Out to 90 degrees from fixation. Far periph Target sizes either 3mm or 10mm 8-12 meridians tested Testing distance is 33cm
Goldman perimetry working distance
extends how far into the periphery?
how to document the size, intensity, and finer adjsustments.
How many meridians tested
30cm working distance 90 degree field Size is 0-V Intensity/brightness is 1-4 Light transmission/fine adjustment is a-e 8 meridians tested
Standard goldman stimulus
III 4 e
0.43 degrees, max brightness, max fine adjustment
Advantages and disadvantages to automated perimetry
Uniform, reproducible, stat analysis, random presentation, screening and threshold, central and peripheral
Expensive, long test time.
How does Automated perimetry Humphrey monitor pt fixation
Video monitoring
-Restests blind spot and monitors K light reflex.
Eye movement increases false negatives
Automated perimetry.
How to calculate working distance lens
- If cyl is less than 1?
- If pt is dilated?
- age based add for perimetry?
Cyl less than 1- use SE Pt dilated- +3.00D Age based 30-40: +1.00 40-45 +.1.50 45-50 +2.00 55-60: +2.50
Automated perimetry
2 trial lens holders
HFA2- trial lens holder to place trial lens power.
HFA3- liquid lens technology loads correction
move out of the way when outside central 30 degrees
Two technologies for FDP (frequency doubling)
Carl Zeiss Meditec and Humphrey Matrix
How does FDP occur
Low spatial frequency grating (fat bars, 0.25cpd) flickers at high temporal frequencies (25Hz)
You perceive 2x as many bars.
Each square is 7x8 degrees
FDP
advantages
Glaucoma sensitivity and specificity
Takes how long to perform screening and how long to perform threshold?
When to use trial lenses for Zeiss and Matrix?
Unaffeced by optical blur, pupil size, ambient illumination. Robust stimulus.
High sensitivity (80%) and specificity (90%)
35 seconds for screening
40 seconds for threshold
Trial lenses at +/- 7.00D for Zeiss, 3 for Matrix
FDP is mediated by which cells?
M cells- magnocelular. 10%
Large diameter that detect motion.
May be most vulnerable to glaucoma damage.
FDP testing pattern
35 degree H, 30 degree vertical.
16 regions plus central circle.
0.25 cpd
25 Hz
Static threshold perimetry. Where does it start? what is the bracketing technique?
Starts test at a single locus (anchor point) in each quadrant of VF. Starts 4dB brighter than the age corrected norm.
If you don’t see it, it will get 2 dB brighter until you see it.
Once the patient sees it, do 4-2-1. Double crossing.
Swedish interactive threshold algorithm for SITA.
Accelerated. Instead of 4-2-1, it is 4-2. Maximum likelihood procedure.
Staircase stops once accuracy is reached.
Humphrey screening 2 zone vs 3 zone
2 zone- starts at age matched norm supra threshold. Gives 1 opportunity to respond. Seen = open circle. Not seen= dark square.
3 zone- tests suprathreshold first.
seen= open circle.
Retests any missed points twice. Second time at lower dB level (brighter). Seen? X
if not seen, tests at 0 dB. Not seen? Absolute defect
C-76 and C-40. are these screening or threshold tests
c= central
Screening
C76 pattern is similar to 30-2.
76 points spaced 6 degrees apart. Tests central 30 degrees from fixation in 4 gazes. Straddles on either size of the midline.
Criteria for progressing to a threshold test
2 or more adjacent missed points
OR
1 or more misses within 20 degrees of fixation
OR
Central references level of 26 dB or less. (has to be really bright)
Clinical indications for central VF testing
Positive risk factors for glaucoma
Neuro- NEW HA, dizzy, numbness.
central vision loss.
Flashes, floaters, diplopia, ptosis.
30-2 SITA Standard/Fast HFIIi
76 points
6 degree separation
30 degree field
central vision loss, glaucoma, symptomatic neuro.
10-2 SITA Standard/Fast HFIIi
68 points
2 degree separation
10 central field
Central vision loss, moderate to end state glaucoma. Amsler grid defects. Risk for maculopathy
24-2 SITA Standard/Fast HFIIi
54 points
6 degree separation
24 degree field
extends 30 degree nasally
glaucoma, ON abnormalities.
HFA3 threshold recommendations for 24-2C SITA FASTER
54 points with 6 deg separation
10 additional central points (64 total) known to be susceptible to glaucoma defect.
Tests VF 50% faster than SITA standard and 30% faster than SITA fast.
Checks for glaucoma
STATPAC
Patient demographic Threshold values in dB Greyscale display Reliability indicies- FP, FN, FL Global indicies
Ideal values for reliable indicies
FLL less than 20%
FP less than 15% Trigger happy
FN less than 33% (Phasing out) Fatigue or inattention
Ideal values for global indicies
Mean Sensitivity (MS)- average of all threshold values.
Total deviation TD- Graph. Probability of each point being abnormal. Could be positive or negative.
Mean deviation MD- Number off to side. Weighted average of values on the TD plot. 0= no deviation from normal. normal values are +/- 2. More affected by cataracts.
PSD- Measure of non uniformity in the shape of the hill of vision. 0 to +2 is normal. Low PSD= Smooth hill of vision. High= irregular hill.
TD vs PSD
Abnormal TD, normal PSD= Cataract. Low thresh.
Normal TD, abnormal PSD= trigger happy. High thresh.
VFI and ranges
Visual field index. Single number that summarizes each patient’s VF status as a percentage of normal age corrected sensitivity.
Estimates the rate of progression of loss. Similar to MD.
100= normal
91-100= early defect
78-91 = moderate defect
less than 78 = severe
GHT
Evaluates 5 zones in the superior field and compared with sensitivity of corresponding areas in the inferior field.
Differences by 4dB or more indicates abnormal
WNL- 1A and 1B similar. No deviation.
ONL- 1A and 1B dissimilar. Less than 1% of normal.
BL boarder line 1-3% of normals
No qualifier- general depression or abnormally high sensitivity.
Severe/advaned defect. 2 signs.
MD less than ???
MD less than 12.01
Any point inside central 5 degrees with threshold of 0.
HFA II Threshold single field analysis
patient demogrpahics Sensitivity levels Greyscale Reliability Global GHF Gaze tracking
Gaze tracking. How does it work and how do you interpret?
Monitors corneal reflex and pupil margin. Doesn’t track head or eye movement.
Downward blip- eye position cannot be determined.
Ptosis, during blink. irreg pupil margin.
Upward- pt looked away. up to 10 degrees
Altiudinal hemianopsia
Superior or inferior defect
Incongrous and congruous
Unequal vs equal VF defects between the two eyes
Nasal step. Assume
Notching. Loss of rim tissue. Vertical CD ratio.
What does a NFL defect look like
Acurate defect + nasal step. Progression of disease from glaucoma.
VF tests for advanced glaucoma
10-2 SITA Fast
Does 10-2 have GHT or VFI values?
NO
MD for early, moderate, and severe defect
Early: -2 to -6
Moderate: -6 to -12
Severe: worse than -12
dB within central 5 degrees for early, moderate, and severe defect
Early- no point within 5 degrees less than 15 dB
Moderate- 1 hemifield containing point less than 15 dB
Severe- Both hemifields contain point less than 15dB
How is SITA faster different from the fast and standard
test sequence starts at age corrected norm.
One stair case reversal test instead of 2
Removed FN feature
Does not present brightest stimulus again that was not responded to prior. Max is 0db or 10,000 abs
Fixation loss tracked by gaze tracker.
Eliminated 300ms delay after non seeing stimulus.
Uses the 24-2 C test pattern. (64 pts)
Takes about 4 mins
VF codes for screening and threshold
92082 screening
92083 threshold
ICD 10 codes for Visual field defect
41 - Central 43 - Arcuate 45 - Localized 46 - Homo 47- hetero 47- constriction
H53.41X
X can be 1, 2 or 3 for OD, OS, OU.
VF defect Paracentreal and nasal sted Paracentral step nasal step Temporal wedge
Percentage of VF lost at dx?
50% 25% 25% 2% Temporal wedge is not a sign of glaucoma, associated with myopia.
