20/20 vision

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20/20 vision is a term used in the field of optometry to denote normal visual acuity, or the clarity or sharpness of vision. The term "20/20" and similar fractions (such as 20/40, 20/60, etc.) are visual acuity measurements. They also serve as an informal benchmark for good vision.

Definition[edit | edit source]

The term "20/20" is derived from a standard system used to measure visual acuity, which is the ability to discern letters or numbers at a given distance according to a fixed standard. The first number in the fraction represents the distance at which the test is performed (20 feet), and the second number represents the distance at which a person with normal vision could read the same line of the chart. Therefore, 20/20 vision means that a person can see clearly at 20 feet what should normally be seen at that distance.

Measurement[edit | edit source]

Visual acuity is typically measured using a Snellen chart, named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862. The chart consists of rows of letters, numbers, or symbols in standardized sizes, with a single large letter at the top and rows of progressively smaller letters below.

Factors affecting 20/20 vision[edit | edit source]

Several factors can affect visual acuity, including refractive error, astigmatism, presbyopia, cataract, macular degeneration, and retinal detachment. These conditions can cause vision to be less than 20/20, requiring corrective measures such as glasses, contact lenses, or surgery.

Misconceptions[edit | edit source]

It is a common misconception that 20/20 vision means perfect vision. However, 20/20 vision only indicates the sharpness or clarity of vision at a distance. Other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision, contribute to your overall visual ability.

See also[edit | edit source]

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Contributors: Prab R. Tumpati, MD