Eye power, or the refractive power of a lens required to correct vision, is measured in diopters.
Here's a more detailed explanation:
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Diopters Explained: A diopter is the unit of measurement used to quantify the optical power of a lens or curved mirror. It essentially describes the degree to which a lens converges or diverges light.
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Focal Length Connection: One diopter is defined as the reciprocal of the focal length of a lens in meters. So, a lens with a focal length of 1 meter has a power of 1 diopter. A lens with a focal length of 0.5 meters (50 cm) has a power of 2 diopters.
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Positive and Negative Diopters:
- Positive diopters indicate a converging lens, which is used to correct farsightedness (hyperopia).
- Negative diopters indicate a diverging lens, used to correct nearsightedness (myopia).
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Measurement Process: Optometrists or ophthalmologists use specialized equipment, such as a phoropter or autorefractor, to determine the refractive error of your eye. These devices help measure the lens power required to focus light correctly on your retina, thus determining your eyeglass or contact lens prescription in diopters. The measurement process can involve subjective tests (patient feedback) or objective tests (automated measurements).
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Prescription Example: A typical prescription might look like: -2.50 diopters for nearsightedness or +1.75 diopters for farsightedness.
