![]() The VFI is an overall marker of field loss similar to the MD. The glaucoma hemifield test (GHT) is a sensitive indicator of differences between the superior and inferior hemifields. Additional key indicators-the global indices-are on right side of the page. The localized defect-a superior nasal step with an arcuate component-caused by the glaucoma is seen on the PD plot. The generalized depression from the cataract is evident on the TD plot (lower left). This patient has a mild cataract and glaucoma. Remember, do not rely solely on the gray scale when evaluating visual fields.Ĥ. Of note, the gray scale does not show the defect, which is due to an interpolation error in the scaling. The large inferior defect is clearly depicted and appears similar on both the total and pattern deviation plots. In this classic example, the patient has moderate to advanced stage glaucoma. 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.Īfter reviewing these key data points, the next part of the page can be evaluated.ģ. The field may often look normal or “cleaner” (with fewer defects depicted) on patients with values of 5% to 10% or higher.įalse negatives are identified when the patient does not respond to a light stimulus that should have been detected, based upon earlier responses. One way to reduce fixation losses is to make sure your technician properly aligns the patient and monitors their attention during the test.įalse positives, another key index, help to identify a “trigger happy” patient who is pushing the response button even when no light stimuli are presented. High fixation losses (more than 15% to 20%) are a strong indication that the test results are likely inaccurate. Examining the reliability indices is the next key step in visual field interpretation ( figure 2). Although a standard test program and pattern (e.g., 24-2, Threshold) is often selected for the majority of patients, be sure to confirm that the correct test was selected. Identify that the proper trial lens was calculated and utilized. Make sure the patient’s birthdate is accurate, because the test results are compared to a normative database. Regardless of the instrument used, start at the top by locating information about the test parameters ( figure 1) and reliability indices. While the printouts from different perimeters do not look identical, much of the displayed content and information is the same. 1 Do not follow old published guidelines of up to a 33% acceptance rate. An error rate of 5% to 10% significantly affects theĪppearance, making the gray scale and other plots appear better than Fixation losses, false positives andįalse negatives are recorded-with false positives often being the mostĬritical. In addition, we can measure the rate of disease change as well, giving us powerful insight to our management. By following a standardized process on all visual field printouts, clinicians can ensure they are accurately diagnosing ocular disease and/or detecting progression.įor individuals, such as glaucoma patients, who have had a series of visual fields, new analyses are available that greatly help our ability to detect a change in VF defects. Good interpretation skills start with a methodical assessment of several key plots, graphs and indices. Given the subjective nature of the test, it’s essential to differentiate true, disease-related defects and abnormalities from artifact and noise.Įvaluating visual field results from any perimeter can be confusing and daunting at times, especially when attempting to cohesively link all the data together. While some of the basic principles of interpretation remain, advances in software and hardware have shortened test-taking time and improved accuracy and reliability. Most commonly, it is used for conditions affecting the optic nerve and other forms of neurological disease but it’s also helpful for retinal conditions and instances when visual field function needs to be measured.Īutomated, computerized and threshold static perimetry became available about 30 years ago. Visual field testing is an important diagnostic consideration in the evaluation of patients with many different types of pathologies. 1 The fixation losses are also noted here. The standard test is better for early detection, while the SITA-Fast test tends to show variable results and is less sensitive. On the Humphrey Field Analyzer (shown here), the best threshold test is the SITA-Standard. The top of the VF printout page contains key information about patient demographics and the type of test that was performed.
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