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2. Prism correction - Wikipedia

   en.wikipedia.org/wiki/Prism_correction

   Prism dioptres. Prism correction is commonly specified in prism dioptres, a unit of angular measurement that is loosely related to the dioptre. Prism dioptres are represented by the Greek symbol delta (Δ) in superscript. A prism of power 1 Δ would produce 1 unit of displacement for an object held 100 units from the prism. [2]

3. Fresnel lens - Wikipedia

   en.wikipedia.org/wiki/Fresnel_lens

   A Fresnel lens (/ ˈfreɪnɛl, - nəl / FRAY-nel, -⁠nəl; / ˈfrɛnɛl, - əl / FREN-el, -⁠əl; or / freɪˈnɛl / fray-NEL[ 1 ]) is a type of composite compact lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections.

4. Binoculars - Wikipedia

   en.wikipedia.org/wiki/Binoculars

   8×42 roof prism binoculars with rainguard and opened tethered lens caps. Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects.

5. Corrective lens - Wikipedia

   en.wikipedia.org/wiki/Corrective_lens

   A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye. Contact lenses are worn directly on the surface of the eye.

6. Prism (optics) - Wikipedia

   en.wikipedia.org/wiki/Prism_(optics)

   Prism spectacles with a single prism perform a relative displacement of the two eyes, thereby correcting eso-, exo, hyper- or hypotropia. In contrast, spectacles with prisms of equal power for both eyes, called yoked prisms (also: conjugate prisms, ambient lenses or performance glasses) shift the visual field of both eyes to the same extent. [5]

7. Adjustable-focus eyeglasses - Wikipedia

   en.wikipedia.org/wiki/Adjustable-focus_eyeglasses

   Adjustable-focus eyeglasses. Adjustable focus eyeglasses are eyeglasses with an adjustable focal length. They compensate for refractive errors (such as presbyopia) by providing variable focusing, allowing users to adjust them for desired distance or prescription, or both. Current bifocals and progressive lenses are static, in that the user has ...