Three different types of eye charts used for measuring visual acuity:

1. Alphabet & Numbers Chart: Made from cardboard, this chart uses a combination of letters and numbers to test vision.
2. SNELLEN CHART: Made from PVC, this is the classic eye chart with rows of letters that decrease in size. It’s widely used in eye exams.
3. Eye Chart E: Also made from PVC, this chart features the letter “E” in different orientations and sizes, commonly used for testing young children or individuals who cannot read.

Eye charts are tools used by eye care professionals to measure visual acuity, which is the clarity or sharpness of vision. Here’s how they work:

1. Positioning: The patient is positioned at a specific distance from the chart, usually 20 feet (6 meters) for a standard Snellen chart. For smaller rooms, mirrors might be used to simulate this distance.

2. Reading the Chart: The patient covers one eye and reads aloud the smallest line of letters they can see clearly. This process is repeated for the other eye.

3. Scoring: Each line of the chart corresponds to a visual acuity score. For example, if you can read the line labeled “20/20,” it means you have normal visual acuity. If the smallest line you can read is labeled “20/40,” it means you see at 20 feet what a person with normal vision sees at 40 feet.