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  2. Progressive lens - Wikipedia

    en.wikipedia.org/wiki/Progressive_lens

    Progressive lenses are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient of increasing lens power, added to the wearer's correction for the other refractive errors. The gradient starts at the wearer's distance prescription at the top of the lens and reaches a ...

  3. Four prism dioptre reflex test - Wikipedia

    en.wikipedia.org/wiki/Four_prism_dioptre_reflex_test

    assess alignment of both eyes. The Four Prism Dioptre Reflex Test (also known as the 4 PRT, or 4 Prism Dioptre Base-out Test) is an objective, non-dissociative test used to prove the alignment of both eyes (i.e. the presence of binocular single vision) by assessing motor fusion. [1] Through the use of a 4 dioptre base out prism, diplopia is ...

  4. Chicken eyeglasses - Wikipedia

    en.wikipedia.org/wiki/Chicken_eyeglasses

    Chicken eyeglasses, also known as chicken specs, chicken goggles, generically as pick guards, and under other names, [2] were small eyeglasses made for chickens intended to prevent feather pecking and cannibalism. They differ from blinders in that they allow the bird to see forward, whereas blinders do not. One variety used rose-colored lenses ...

  5. Corrective lens - Wikipedia

    en.wikipedia.org/wiki/Corrective_lens

    Corrective lens. A pair of contact lenses, positioned with the concave side facing upward. 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.

  6. Lensmeter - Wikipedia

    en.wikipedia.org/wiki/Lensmeter

    13 – Prism scale knob. A lensmeter or lensometer (sometimes even known as focimeter or vertometer), [1] [2] is an optical instrument used in ophthalmology. It is mainly used by optometrists and opticians to measure the back or front vertex power of a spectacle lens and verify the correct prescription in a pair of eyeglasses, to properly ...

  7. Aspheric lens - Wikipedia

    en.wikipedia.org/wiki/Aspheric_lens

    An aspheric lens or asphere (often labeled ASPH on eye pieces) is a lens whose surface profiles are not portions of a sphere or cylinder. In photography, a lens assembly that includes an aspheric element is often called an aspherical lens . The asphere's more complex surface profile can reduce or eliminate spherical aberration and also reduce ...

  8. Dioptre - Wikipedia

    en.wikipedia.org/wiki/Dioptre

    A dioptre ( British spelling) or diopter ( American spelling ), symbol dpt, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dpt = 1 m−1. It is normally used to express the optical power of a lens or curved mirror, which is a physical quantity equal to the reciprocal of the focal length ...

  9. Fixation disparity - Wikipedia

    en.wikipedia.org/wiki/Fixation_disparity

    Eye glasses with an included prism power is the optical method to reduce a fixation disparity. Different procedures have been proposed to determine the required amount of prism for the individual. Based on prism-FD curves (Fig. 3b), one can find the aligning prism sP 0 that nullifies the naturally prevailing fixation disparity sFD 0. This test ...