Foundations Of Visual Field Interpretation Flashcards
Threshold determination
Age matches normal data are used to compare patients data -normal range determined by: —Sensitivity of each retinal point —upper 95% as normal —lower 5% as abnormal
When is suprathreshold used for
Disability and driving
The lower the decibels
The brighter the stimulus
The part of the visual field that corresponds to the fovea
Fixation
Localized defects/depressions surrounded by normal vision
Scotoma
Defect that persists when the maximum stimulus is used, e.g. blind spot
Absolute scotoma
Defect that is present to weaker stimulus but disappears with brighter stimulus
Relative scotoma
Reduction both peripheral and centrally
Generalized depression
-cataract
Peripheral depression
RP
Which VF has the least amount of points tested
24-2
What is 10-2 used for
Extreme glaucoma
Plauqeunil
60 points 2 degrees apart
10-2
54 points 6 degrees apart
24-2
74 points
30-2
What are the reliability parameters
Fixation loses
False positives
False negative
If the VF is not normal…
- what was the fixation loss
- what was the false positive and false negative %
- were they properly refracted
- do they have a ptosis/heavy
What is the most reliable relaibiltoy parameters
False positive
Trigger happy patients, responses to stimuli when no target is present
False positive
What si considered unreliable FP
> 33%
-if the FP exceeds 15% the field is considered unreliable and should be re run
Failed to response to suprathreshold stimuli, indicates fatigue, inattentivenss
FN
Clover leaf pattern
FN
What is considered unreliable with FN
> 33%
Fixation loses
Monitored by blind spot and gaze tracking
If the FL rate exceeds ____ it is flagged
20%
Threshold sensitivities measured at each test point, indicated in decibels
Numeric grid
___ dB indicates the max brightness target available for that test
0
Raw data
Numeric grid
Where should numbers be the greates in the numeric gird
In the center, less in the periphery
If there is <0 on numeric grid
Does not mean totally blind int hat spot but that the patient could not see the largest and brightest target available for that test
Provides an approximate picture of the field, good for patient education
Gray scale
Appears as numbers and graphics in the central left area of the printout, represents the difference between the measures threshold of each individual tests location and the age corrected normal vale for that location
Total deviation plot (dB); upper plot
Negative values for the total deviation plot; upper plot
Indicate sensitivities which are below the median age-corrected sensitivity
Positive values in the goal devation plot; upper plot
Indicate sensitivities which are above the median age corrected sensitivity
Graphics display plots the signicance 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. See p value
Total deviation plot (dB); lower plot
Indicates ALL test locations that are outside a normal range
Total deviation plot
Most common reasons for overall reduction or generalized depression
Cataracts
Incorrect trial lenses
Poor test taker
Takes the total deviation plot and adjusts it upwards to downwards to screen out generalized depression, highlights only significant localized VF loss
Pattern deviation plot
Symbols for pattern deviation plot
Uses the same symbols as the total deviation plot to show points which are significantly worse than normal P value
Single most uself analysis on an SFA printout
Pattern deviation plot
Highlights subtle, but significant localized variations that might otherwise be masked, early defects show up sooner on probability map than on gray scale plot
Pattern deviation plot
It total deviation plot and pattern deviation are about the same
There is little to no generalized loss
If abnormal TD plot and normal PD plot
Cataract, incorrect Rx
If normal TD plot and abnormal PD plot
Trigger happy
Significance of deviations from Normal in the probability plots (P value)
Indicated in the total deviation probability plot (P value)
A 2% symbol indicates that fewer than 2% of normal patients have a sensitivity
That low or lower
Found on the lower right hand corner of the printout, single number representations of the VF, MD, PSD
Global indices
Shows how much (on average) the whole field departs from normal
Mean deviation
(+) MD
Better than average
(-) MD
Less than average
Abnormal MD
P<0.5%
-less than 0.5% of the population has a mean deviation larger than the value found on the test
Height of the hil of vision compared to age matched normals.
MD
Measures the extent to which the threshold determinants at different locations differ from each other
Pattern standard deviation (PSD)
This does not change with media (cataract)
Pattern standard deviation (PSD)
The higher the PSD, the more
Irregular the pattern
-high PSD=more localized defects=more indicative of pathology
Indicates the SHAPE of the hill of the vision
Pattern standard deviation
If MD is abnormal and the PD is normal
Generalized defect
Normal MD and abnormal PD
Small localized defect
MD and PD both abnormal
Large defect with a localized components
Interpretation and report
- look at both eyes together
- does the field make sense compared to other clinical findings
- make sure data trustworthy
- evaluate defect; any type of defect
- repeatability of the defect
- probable diagnosis
Documentation of HVF
- make statements referencing reliability
- make statement regarding pattern, depth, and size of VF loss
- make statements which correlates other exam findings with the VF
- always remember to wrtie signature next to signatures
Reasons for VF defect
- glaucoma
- retinal abnormalities
- developmental optic disc anomalies
- optic neuropathies
- chiasmal lesions
- homonymous hemianopia
- functional vision loss
Glaucomatous progression rate
Almost 10x faster than the normal rate of decline of visual function with age
-structural change usually precedes loss but not always
Neuro causes of field loss
Stroke
Optic neuritis/neuropathy
Chiasmal tumors
Raised intracranial pressure
Visual field defects obey
Anatomy
Interpretation of the VF loss reveals the
Location
Finding the location of the VF loss reveals the
Lesion
Clues from exam
VA
Confrontational VF
RAPD
Color vision
How does a droopy lid appear on a VF?
Looks like an accurate defect
Ring defect on VF
Lens artifact
Small pupil in VF
Lack of peripheral
Ptosis
Superior field defects
Called the true positive rate. Defined as the proportion of people with the disease who will have a positive result
Sensitivity
A highly sensitive test is one that does what
Correctly identifies patients with a disease
A test with 100% sensitivity will identify
All patients who have the disease
If a person has a disease, how often will the test be positive (true positive rate)?
Sensitivity
If the test is highly sensitive and the test result is negative you can be certain
That he don’t have disease
A ______ helps rule out disease when the result is negative
Sensitivity
TP/(TP+FN)
Sensitivity
The specificity of a test (also called the TN rate) is the proportion of people without the disease who will have a negative result
Specificity
Refers to how well a test identifies patients who do not have a disease
Specificity of a test
A test that has 100% specificity will identify
100% of patients who do not have the daises
If a person does not have the diasease, how often will the test be negative (TN. Rate)
Specificity
If the test result for a highly specific test is positive you can be certain that
They actually have the disease
TN/(TN + FP)
Specificity
High sensitivity tests have low
Specificity
-they are good at catching actually cases of the disease but they also come with a fairly high rate of false positive (mammograms)
Low sensitivity/high specificity
UTI
