From the Guidelines
Central fixation losses on Humphrey Visual Field Analyzer test results are most likely explained by patient inattention or fatigue during the examination. These fixation losses occur when the patient's gaze drifts from the central fixation target, causing them to miss stimuli or respond incorrectly. Common causes include difficulty maintaining concentration throughout the test (which typically lasts 5-10 minutes per eye), physical discomfort from sitting still, eye fatigue, or poor understanding of test instructions. Elderly patients, those with cognitive impairments, or individuals with severe visual field defects may experience higher rates of fixation losses. To minimize these losses, patients should be properly positioned with appropriate refractive correction, given clear instructions, and allowed breaks if needed during testing. The technician should monitor the patient throughout the test and provide gentle reminders to maintain fixation. Clinically, fixation losses exceeding 20% may compromise test reliability and should prompt consideration of repeating the test or interpreting results with caution, as high fixation loss rates can lead to artificially depressed visual field sensitivity measurements.
Some possible explanations for central fixation losses include:
- Patient inattention or fatigue during the examination 1
- Difficulty maintaining concentration throughout the test 1
- Physical discomfort from sitting still or eye fatigue 1
- Poor understanding of test instructions 1
- Elderly patients, those with cognitive impairments, or individuals with severe visual field defects may experience higher rates of fixation losses 1
In the context of the provided Humphrey Visual Field results, a fixation loss of 14/15 suggests that the patient may have had difficulty maintaining fixation during the test, which could be due to various factors such as inattention, fatigue, or physical discomfort. It is essential to consider these factors when interpreting the test results and to take steps to minimize fixation losses in future tests.
Given the information provided, the most likely explanation for the central fixation losses is a combination of patient inattention and fatigue during the examination, as this is a common cause of fixation losses in visual field tests 1. However, it is crucial to consider other potential factors and to take a comprehensive approach to interpreting the test results.
From the Research
Explanation of Central Fixation Losses
The central fixation losses on Humphrey Visual Field test results can be attributed to several factors, including:
- Patient's inability to maintain steady fixation throughout the test
- Patient shifting their head after the blind spot was plotted
- Trigger-happy patient
- Patient falling asleep during testing
Most Likely Explanation
Based on the provided studies, the most likely explanation for central fixation losses is:
- Unsteady fixation throughout the duration of the test 2 This is because the study found that gaze tracking parameters are closely related to the reproducibility of visual field results, and fixation losses are an important factor in determining the reliability of the test.
Other Possible Explanations
Other possible explanations for central fixation losses include:
- Patient shifted head after blind spot was plotted 3
- Trigger-happy patient 3
- Patient falling asleep during testing 3 However, these explanations are not directly supported by the studies, and the most likely explanation is unsteady fixation throughout the duration of the test.
Study Findings
The studies found that:
- Fixation losses are an important factor in determining the reliability of visual field tests 2, 4
- The Humphrey Visual Field Analyzer is a reliable tool for detecting visual field defects 3, 5
- The test results can be affected by various factors, including patient's cooperation and fixation stability 2, 3