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The Snellen Vision Chart is an eye chart used by optometrists and ophthalmologists to measure visual acuity. It consists of multiple rows of letters that decrease in size as you move down the chart. Here’s a detailed description: Layout and Design: The chart typically has 11 rows of capital letters. The top row features a single large letter, usually an "E." Each subsequent row contains more letters that progressively decrease in size. The smallest letters are found in the bottom rows. Measurements and Usage: The test is conducted at a standard distance, usually 20 feet (6 meters) from the chart. Each row is labeled with a fraction (e.g., 20/20, 20/40, 20/200) to indicate visual acuity. 20/20 vision means the person can read at 20 feet what a person with normal vision can read. 20/40 vision means the person must be at 20 feet to read what a normal-sighted person can read at 40 feet. 20/200 vision or worse is considered legally blind. Types of Snellen Charts: 1. Standard Snellen Chart – Uses letters (most common). 2. Tumbling E Chart – Uses only the letter "E" in different orientations for those who can't read. 3. Landolt C Chart – Uses circles with gaps in different positions for non-literate individuals. 4. Picture or Symbol Charts – Used for children and non-verbal individuals.
