VF Interpretation Flashcards
How are fixation losses monitored
Gaze tracking and blind spot monitoring
Gaze tracking
- located at the bottom of the chart
- records deviation from correct fixation as upward deflections
- downward spikes are eyelids or eyelashes interrupting view (blink)
- if the FL rate exceeds 20% it is flagged
Blind spot monitoring
- number of time a patient responds to a target placed in the blind split
- 10% of all stimulus is presented in the blind splint areas
Numeric grid
- ther threshold sensitivities measured at each test point
- indicated in Db
- 0 dB indicates the max brightness target available for that test
- numbers should be the greates in the center, less in periphery
- look for abnormally high or low values
- even if <0 does not mean blind, they couldn’t see that target
Grayscale printout
- appx of field
- patient education
- resembles Isopters in a gray tone
- little clinical relevance
- SHOULD NOT BE USED IN THE ANALYSIS OF THE FIELD
Total deviation plot (dB); upper plot
- appears as numbers and graphics in the central left area of the print out
- represents the difference between the measured threshold of each individual test location and the age corrected normal value for that location
Negative total deviation plot upper plot
Indicate sensitivities which are below the median age corrected sensitivities
Positive values for the total deviation plot upper plant
Indicate sensitivities which are above the medial age corrected sensitivity
Total deviation plot; lower plot
- plots the significance of deviations found in the upper plot
- using a small dot for a point within the range of 95% of the normal values or with a shaded box (outside of 95% of normal values indicating suspicion for abnormality)
- see p value
Most common reasons for overall reduction or generalized depressions in the total deviation plot
Cataracts
Incorrect trial lenses
Poor test takers
Pattern deviation plot
- takes the total deviation plot and adjusts it upwards to downwards to screen out generalized depression
- highlights only significant localized visual field loss
- uses ther same symbols as the total deviation plot to show points which are significantly worse than normal (p value)
- single most useful analysis on the SFA printout
- highlights subtly, but significant localized variations that might otherwise be masked
- early defects show up sooner on pattern probability map than on grayscale
Total deviation vs pattern deviation
- if total deviation plot and pattern deviation plot are about the same, the there is little to no generalize loss
- if abnormal TD plot and normal PD plot=cataract, incorrect Rx, etc
- if abnormal TD plot and abnormal PD plot=trigger happy. Abnormally high sensitivity
P value (probablitle plots)
-sensitivities are worse then those found in 5%, 2%, 1%, and o.5% of normal patietns with the same age as the patient being tested are highlighted with corresponding symptoms
Glaucoma hemififled test
- compares pattern deviations probability scores in 5 zones in the upper field to mirror image zones in the lower field
- sensitivity differences between upper and lower hemiofields are a hallmark of glaucomtous field loss
Language classifications of threshold
- outside normal limits
- borderline
- generalized depression of sensitivity or abnormally high sensitivity
- within normal limits
Glaucoma respects the ____ midline
Horizontal
Neuro probs respect the ______ midline
Vertical
Outside normal limits in GHT
Sensitivities in one or more Tom the five zones in the upper half of the field are significantly different from the sensitivities measured in corresponding zones int he lower half of the field
P=0.5
Means there is a 95% confidence