Definition

Noun: A standardized assessment of a person's clarity of vision (visual acuity), typically performed at a distance of 20 feet (or 6 meters), using a chart displaying rows of letters or symbols that progressively decrease in size. The test is named after the Dutch ophthalmologist Herman Snellen, who invented the chart in 1862.

Usage

The Snellen test is a fundamental procedure in optometry and ophthalmology. It is used to determine the smallest letters a person can read on a Snellen chart, which is used to calculate a visual acuity score (e.g., 20/20 vision).

Examples

• Noun:
  • During my eye exam, the optometrist administered a Snellen test to check my distance vision.
  • A standard Snellen test involves covering one eye and reading the letters on the chart from the top row downward.
  • The results of the Snellen test indicated that I needed a new prescription for my glasses.

Advanced Usage

• "to fail a Snellen test": To perform below the standard threshold (often 20/40) on this vision test, which may indicate a need for corrective lenses or further examination.
  • He failed the driver's license Snellen test, so he had to get glasses before he could pass.

Variants and Related Words

• Snellen chart (n): The specific eye chart used to conduct a Snellen test. It traditionally features 11 rows of block letters.
• Visual acuity test (n): The general category of tests to measure sharpness of vision, of which the Snellen test is the most common type.
• LogMAR chart (n): A more modern, scientifically precise type of eye chart that is sometimes used as an alternative to the traditional Snellen chart.

Synonyms

• Eye chart test: A more general, informal term.
• Vision screening: A broader term that may include the Snellen test as one component.

Related Phrases

• "20/20 vision": A term originating from Snellen test notation, meaning normal visual acuity. The first number is the testing distance (20 feet), and the second number is the distance at which a person with normal vision could read the same line.
• "Read the bottom line": A common phrase used during the test, referring to the smallest, lowest line of letters on the chart.

Noun

1. a test of visual acuity using a Snellen chart