What is a notable feature of the Snellen chart?

The Snellen chart is primarily designed to measure visual acuity, and a notable feature is that different letters on the chart subtend the same angle at the eye when viewed from a standard distance. This means that regardless of the letter's size, the degree of detail the eye has to resolve is constant, which allows for a standardized way to quantify vision quality.

This feature is critical for ensuring that the visual acuity results are consistent and comparable across different patients and testing environments. The letters are calibrated so that as the size decreases, the ability to identify them becomes a measure of visual acuity, hence the standardization in how the letters are presented is crucial for accurate assessment.

Options suggesting that the Snellen chart measures color vision, includes numbers instead of letters, or assesses peripheral vision do not accurately describe its function. The chart is solely focused on assessing central visual acuity through the recognition of letters.