What is Landolt’s experiment?

Landolt's experiment, also known as the Landolt C test or Landolt ring, is a visual acuity test used to assess a person's ability to discern and identify visual details. It is commonly used in optometry and ophthalmology to measure a patient's visual acuity, specifically their ability to see fine details and discriminate between different orientations of visual stimuli.

In the Landolt's experiment, the patient is presented with a circular target called a Landolt C. The Landolt C consists of a circular ring with a gap in one of its sides, creating a "C" shape. The orientation of the gap varies randomly in each presentation. The Landolt C is usually displayed at a standardized distance, and the patient is asked to identify the direction of the gap by indicating its position, such as pointing towards the gap or stating its location (e.g., top, bottom, left, right).

The Landolt's experiment measures visual acuity by determining the smallest size at which a person can correctly identify the orientation of the gap. The test is typically conducted using a series of Landolt C targets of decreasing size. The visual acuity is expressed as a ratio called the Snellen fraction, with 20/20 representing normal visual acuity.

The Landolt's experiment is a widely used and standardized method to evaluate visual acuity, particularly in assessing refractive errors like nearsightedness (myopia) or farsightedness (hyperopia) and determining the need for corrective lenses. It helps determine the clarity of a person's vision and can be an essential tool in diagnosing and monitoring visual conditions.