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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.
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.
Glasses affect the position by changing the person's reaction to focusing. Prisms change the way light, and therefore images, strike the eye, simulating a change in the eye position. Surgery. Strabismus surgery does not remove the need for a child to wear glasses. Currently it is unknown whether there are any differences for completing ...
By shifting the focus of the target image. This is typically achieved by making the objective lens group of the telescopic sight adjustable so the target focus can be moved into coplanarity with a fixed reticle. These models are often called adjustable objective (AO or A/O for short) models.
Prism correction. Prism lenses (here unusually thick) are used for pre-operative prism adaptation. Eye care professionals use prism correction as a component of some eyeglass prescriptions. A lens which includes some amount of prism correction will displace the viewed image horizontally, vertically, or a combination of both directions.
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.
Belay glasses are eyeglasses with prismatic lenses that are used by belayers in rock climbing to avoid the neck strain associated with belaying.
Adjustable-focus eyeglasses might be used to replace bifocals or trifocals, or might be used to produce cheaper single-vision glasses (since they do not have to be custom-manufactured for every person).
The Peli Lens is a mobility aid for people with homonymous hemianopia. It is also known as “EP” or Expansion Prism concept and was developed by Dr. Eli Peli of Schepens Eye Research Institute in 1999. It expands the visual field by 20 degrees.
Joshua D. Silver is a British physicist whose discoveries have included a new way to change the curvature of lenses, with a significant application for the low-cost manufacture of corrective lenses and adjustable spectacles, especially in low-income countries.