Snellenruutuja
Snellenruutuja, often translated as Snellen chart or E-chart, is a visual acuity test used by eye care professionals to determine the sharpness of a person's vision. Developed by Dutch ophthalmologist Herman Snellen in the 1860s, the chart consists of rows of letters, numbers, or symbols that progressively decrease in size from top to bottom. The individual being tested is asked to read the smallest line they can clearly distinguish from a standardized distance. This distance is typically 20 feet (or 6 meters) in a well-lit room.
The results of a Snellen chart test are expressed as a fraction, such as 20/20. The top
Variations of the Snellen chart exist for different purposes. The "E" chart, also known as a tumbling