Snellentáblával

Snellentáblával is a term that can refer to a few different concepts, often related to vision testing or visual acuity. In the context of ophthalmology and optometry, it most commonly refers to a chart used to measure how well a person can see at various distances. This chart typically displays lines of letters or symbols of decreasing size, arranged in a specific order. The individual being tested is asked to read the smallest line they can discern.

This type of chart is a fundamental tool for diagnosing refractive errors such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. It is also used to assess visual acuity in general, which is a key component of a comprehensive eye examination. The Snellen chart, named after Dutch ophthalmologist Herman Snellen who developed it in the 1860s, is the most well-known example.

The results of a Snellentáblával test are usually expressed as a fraction, such as 20/20. The top number represents the distance in feet at which the test is conducted, and the bottom number represents the distance at which a person with normal vision could read that same line. Therefore, 20/20 vision indicates that the individual can see at 20 feet what a person with normal vision can see at 20 feet. A lower bottom number, like 20/40, means the individual's vision is poorer than normal.