Eye chart

Eye chart is a chart used by optometrists and ophthalmologists to measure visual acuity. Eye charts are often used in various healthcare settings, including clinics, hospitals, and schools.

History

The first eye chart was developed by Herman Snellen in 1862. The Snellen chart is still in use today, although many other types of eye charts have been developed since then.

Types of Eye Charts

There are several types of eye charts used in the field of optometry and ophthalmology. These include:

• Snellen chart: This is the most commonly used eye chart. It consists of 11 lines of block letters, with the size of the letters decreasing as you move down the chart.

• LogMAR chart: This chart is used for more precise measurements of visual acuity. It uses the same principle as the Snellen chart, but the letters are arranged in a logarithmic scale.

• Tumbling E chart: This chart is used for people who cannot read, such as young children or illiterate adults. It consists of rows of the letter 'E' facing in different directions.

• Landolt C chart: This chart is similar to the Tumbling E chart, but it uses a broken ring or 'C' instead of the letter 'E'.

How Eye Charts Work

Eye charts work by measuring how well a person can see details at a specific distance. The person is asked to read the smallest line of letters they can see from a distance of 20 feet. The results are then expressed as a fraction, with the numerator being the distance the person was from the chart and the denominator being the distance at which a person with normal vision could read the same line.

Limitations of Eye Charts

While eye charts are a useful tool in measuring visual acuity, they have some limitations. They do not measure peripheral vision, depth perception, color perception, or the ability to perceive contrast. They also do not measure the health of the eye itself.

See Also

• Visual acuity
• Optometry
• Ophthalmology

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