A visual field refers to the entire area an individual can see at one time, including central and peripheral vision. This wide scope of sight allows for awareness of surroundings without moving the eyes or head. Peripheral vision, the outer edges of this field, plays a significant role in daily activities like navigating environments and detecting movement. The Esterman visual field test is a standardized method used to evaluate this comprehensive visual field, assessing how well a person perceives stimuli across a wide angular range.
Purpose of the Esterman Test
The Esterman visual field test assesses functional, binocular vision, evaluating both eyes working together to perceive the visual world. This test is widely adopted by governmental licensing agencies, such as the Driver and Vehicle Licensing Agency (DVLA) in the UK and state DMVs in the US, to determine fitness to drive safely. It helps ensure drivers possess the peripheral awareness needed for road safety, detecting other vehicles, and avoiding obstacles.
Certain medical conditions, including advanced glaucoma, diabetes, stroke, head injuries, and brain tumors, can affect peripheral vision, making this test a standard requirement for road safety. Beyond driving, the Esterman test also assesses visual disability claims and suitability for specific occupations requiring a wide field of vision. Its broad field of view, covering over 130 degrees, meets many state licensing requirements.
The Testing Procedure
When undergoing an Esterman visual field test, a patient sits at a specialized machine called a perimeter, with their head positioned on a chin rest and headrest. They are instructed to look straight ahead at a central fixation target. Small, flashing lights appear at various locations within their peripheral vision, and the patient presses a button.
The test is performed with both eyes open, simulating real-world binocular vision, and typically takes only a few minutes. Patients are usually advised to wear any corrective lenses they normally use for driving. The procedure is non-invasive and generally painless.
Interpreting the Results
The Esterman test generates a map of the patient’s binocular visual field, typically based on a grid of 120 test points spread across a wide field of view, approximately 136 degrees. Each point corresponds to a specific location, and the test records whether the patient saw the light stimulus. Results are often presented as a score or percentage of total points seen. White circles on the map usually represent points seen, while black squares indicate missed points.
For driving standards, specific criteria apply, which can vary by licensing authority. Generally, a minimum horizontal field of vision of at least 120 degrees is required. There should also be no significant defects within 20 degrees of the central fixation point, either above or below the horizontal midline.
A single isolated missed point is usually acceptable. However, a cluster of four or more missed points, or a cluster of three along with another missed point within the central 20-degree area, may result in a failed test. Licensing authorities consider the overall pattern of missed points, especially those in areas important for driving, such as the lower visual field, which is considered more useful than the upper field.
A failed Esterman test can lead to further evaluation by an ophthalmologist or optometrist, or potentially restrictions on a driving license, such as a conditional license or refusal. Reliability scores, including fixation losses and false positives, are also considered to ensure the accuracy of the test results.