What is a common, non-invasive test for measuring visual acuity?

The Snellen chart test is widely recognized as a standard method for measuring visual acuity. It consists of a series of letters (or symbols) that are displayed in varied sizes, allowing an individual to identify the smallest line of text they can read from a designated distance, typically 20 feet in the United States. This test provides an objective measure of how well a person can see at a distance, which is essential for evaluating overall eye health and vision capabilities.

The test's design is simple; it enables both clinicians and patients to understand and assess visual acuity easily. Typically, the results are expressed as a fraction, where the top number indicates the testing distance, and the bottom number indicates the distance at which a person with normal vision could read the same line on the chart.

Understanding this test is crucial as it forms the basis for various applications in optometry, including determining the need for corrective lenses, monitoring changes in visual acuity over time, and assisting in the diagnosis of various eye conditions.