The Humphrey Visual Field (HVF) test is a common, non-invasive eye examination designed to measure the full scope of your peripheral and central vision. This automated procedure, also known as perimetry, assesses the entire area you can see while focusing on a central point. It involves presenting lights of varying intensities at different locations within your visual field. The test charts your perception of these lights, comparing them to the results of a healthy eye of a similar age to identify any potential damage.
Why the Test is Performed
The Humphrey Visual Field test detects and monitors various conditions that impact your visual field. This assessment is particularly useful for identifying issues early and tracking their progression over time.
Glaucoma is the most common reason for performing an HVF test. This disease often affects peripheral (side) vision first, and patients may not notice changes initially because the deficits can be subtle, and the other eye might compensate. The test helps detect specific changes in peripheral vision caused by glaucoma, such as a nasal step or paracentral scotoma, which are patterns of low sensitivity points in the visual field. Regular testing helps eye care professionals determine if the disease is stable or worsening, allowing for adjustments to treatment plans.
Other neurological conditions, such as stroke, brain tumors, or multiple sclerosis, can also affect the visual field and benefit from HVF testing. For example, optic neuritis, an inflammation of the optic nerve often associated with multiple sclerosis, can cause visual field defects like a central scotoma. The test helps identify these defects, providing information about the location of disease processes or lesions along the visual pathway, including those in the brain’s visual cortex. Retinal diseases, like retinitis pigmentosa, and optic nerve damage can also be detected and monitored using this test.
The Testing Experience
Before your Humphrey Visual Field test, bring your glasses if you wear them for distance vision. Avoid heavy eye makeup, as it might interfere with the machine’s sensors or your comfort. Inform the technician about any physical limitations, such as back pain or difficulty sitting still, so they can help you remain comfortable during the procedure.
During the test, you will sit in front of a large, bowl-shaped instrument with your head placed on a chin rest. You will be asked to focus on a central target light directly in front of you. Tiny lights of varying intensities will then appear briefly (around 200 milliseconds) at different, random points within the dome. Each time you see a light, you press a button on a handheld remote control. It is normal for some lights to be very dim or appear quickly, and you might not see every single one.
The test is performed one eye at a time, with the other eye covered to ensure accurate results. The machine continuously monitors your gaze to ensure you maintain focus on the central target, as looking away can affect the reliability of the results. If you experience fatigue or need to blink, you can ask the technician for a brief pause. The entire procedure typically takes about 5 to 20 minutes per eye, depending on the specific test program used and your response time. The test is non-painful, and your comfort is a priority throughout the examination.
Understanding Your Results
After completing the Humphrey Visual Field test, your results are typically presented as a detailed printout or map. This printout shows various plots and indices that help your eye care professional interpret your vision. It includes a grayscale map, which visually represents the sensitivity of your visual field, with darker areas indicating reduced sensitivity or vision loss.
Eye care professionals analyze the patterns of any detected defects. For instance, specific patterns like arcuate scotomas or nasal steps are often indicative of glaucoma. Other patterns, such as hemianopia, where vision loss occurs in half of the visual field, can suggest neurological conditions like stroke or brain tumors. The printout also includes numerical plots showing the threshold of light sensitivity at each tested point and statistical data comparing your results to those of an age-matched healthy population.
Comparing current results with previous tests is an important part of monitoring progression of any condition. This allows the doctor to track changes in the size, shape, and depth of any visual field defects over time. Your eye care professional will discuss these results with you, placing them in the context of your overall eye health, medical history, and findings from other diagnostic tests. Ask your doctor to explain what specific areas of the visual field map mean for your vision and how the results might influence your treatment plan.