How accurate is visual field test?
How accurate is visual field test?
Results: Overall, patients performed reliably in 52% of visual field tests. The most common cause of poor reliability was fixation loss, with 43% of patient tests deemed unreliable due to a fixation loss rate greater than 20%.
What percentage of false positives is considered poor reliability in a visual field test?
According to the manufacturer of the Humphrey Field Analyzer (HFA; Carl Zeiss Meditec, Dublin, CA), visual field test results of patients whose fixation losses exceed 20% or whose false-positive or false-negative errors exceed 33% are not considered reliable.
What are false negatives in visual field tests?
False negatives are identified when the patient does not respond to a light stimulus that should have been detected, based upon earlier responses. Values of 10% to 15% or more are indicative of a patient who is not paying good attention during the course of the test; the results may look worse than they really are.
Can you drive with visual field loss?
A diagnosis of hemianopia, or blindness in one half of the visual field in both eyes as the result of strokes, tumors or trauma often means the end of driving. In about half of the states in the United States and in many other countries, driving with hemianopia is prohibited.
What is the visual field plot from suprathreshold perimetry?
The visual field plot from suprathreshold perimetry usually consists of a series of dots or circles indicating the stimulus locations tested during the visual field examination and a numerical value showing the threshold level of the patient from which the suprathreshold level was set.
What is the difference between threshold testing and Suprathreshold testing?
In suprathreshold tests, an intensity of pre-determined brightness is employed at each test location. Thus, the precise sensitivity of each test location is not known. In threshold testing, an attempt is made to measure the intensity of the dimmest stimulus which can be detected 50% of the time.
How do you test for normal visual fields?
A comparison of examiner and patient fields is made, the assumption being that you, as the examiner, have normal visual fields (this is another reason why you should undergo visual field testing yourself). First test the binocular visual field and then test each eye separately.
How is the Humphrey perimeter used for visual field tests?
The Humphrey perimeter uses background lighting of 31.5 abs to saturate rod photoreceptors, producing photopic conditions in which cones are primarily tested. Visual field tests employ either threshold or suprathreshold algorithms. In suprathreshold tests, an intensity of pre-determined brightness is employed at each test location.
