näöntarkkuusmittaus

Näöntarkkuusmittaus, often translated as visual acuity measurement, is a fundamental test in optometry and ophthalmology used to determine the clarity of vision. It assesses how sharply an individual can discern fine details at a specific distance. The most common method employs the Snellen chart, a standardized wall chart featuring letters or symbols of decreasing size. Patients are asked to read the smallest line they can clearly distinguish from a set distance, typically 20 feet (or 6 meters).

The results are expressed as a fraction, such as 20/20. The top number represents the distance at which the test is performed, and the bottom number indicates the distance at which a person with normal vision could read the same line. Therefore, 20/20 signifies normal visual acuity. A result like 20/40 means the individual can only see at 20 feet what a person with normal vision can see at 40 feet, indicating poorer acuity. Conversely, 20/15 suggests better-than-normal vision.

Näöntarkkuusmittaus can be performed under various conditions, including with and without corrective lenses (glasses or contact lenses), to assess both uncorrected and corrected vision. This measurement is crucial for diagnosing refractive errors like myopia (nearsightedness), hyperopia (farsightedness), and astigmatism, as well as for monitoring the progression of eye diseases and evaluating the effectiveness of treatments. It's a quick, non-invasive, and essential part of any comprehensive eye examination.