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Vision (unaided) VA Visual acuity VA Dcc - VA Dsc Visual acuity with Distant chart with correctors Visual acuity with eye chart at Distant 20 feet (6 m) and with (cc: Latin cum correctore) correctors (spectacles); Dsc is without (sc: Latin sine correctore) correctors. See Visual_acuity#Legal_definitions: VA Nsc - VA Ncc
Adjustable focus lenses, like single-focus lenses, also reduce image-jump and spatial distortion in the field of view associated with traditional multi-focal lenses. Additionally, the ideal near-vision correction can be achieved with precision, because the variable lenses emulate the focusing action of the youthful (non-presbyopic) eye.
The T-mount is a standard lens mount for cameras and other optical assemblies. The usual T-mount is a screw mount using a male 42×0.75 (42 mm diameter, 0.75 mm thread pitch) metric thread on the lens with a flange focal distance of 55 mm and a mating female 42mm thread on a camera adapter or other optical component.
This may represent a single-vision lens prescription to improve near work, or the reading portion of a bifocal lens. OD is an abbreviation for oculus dexter, Latin for right eye from the patient's point of view. Oculus means eye. OS is an abbreviation for oculus sinister, Latin for left eye from the patient's point of view.
Secondary lens refers to a multi-element lens mounted either in front of a camera's primary lens, or in between the camera body and the primary lens. (D)SLR camera & interchangeable-lens manufacturers offer lens accessories like extension tubes and secondary lenses like teleconverters , which mount in between the camera body and the primary ...
The add segment of the lens for near vision is the D-shaped area. A bifocal is a lens with two sections, separated by a line (see image to the right). Generally, the upper part of the lens is used for distance vision, while the lower segment is used for near vision. The area of the lens that caters to near vision is called the add segment.