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Base curve radius (BCR) or simply base curve (BC) is the measure of an important parameter of a lens in optometry. On a spectacle lens, it is the flatter curvature of the front surface. On a contact lens it is the curvature of the back surface and is sometimes referred to as the back central optic radius (BCOR). Typical values for a contact ...
A contact lens rests directly on the surface of the cornea and moves in sync with all eye movements; consequently, a contact lens is always almost perfectly aligned on center with the pupil, and there is never any significant off-axis misalignment between the pupil and the optical center of the lens.
Radius of curvature sign convention for optical design. Radius of curvature (ROC) has specific meaning and sign convention in optical design.A spherical lens or mirror surface has a center of curvature located either along or decentered from the system local optical axis.
As of 2010, the average age of contact lens wearers globally was 31 years old, and two-thirds of wearers were female. [4] People choose to wear contact lenses for many reasons. [5] Aesthetics and cosmetics are main motivating factors for people who want to avoid wearing glasses or to change the appearance or color of their eyes. [6]
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Plots of film density (log of opacity) versus the log of exposure are called characteristic curves, [3] Hurter–Driffield curves, [4] H–D curves, [4] HD curves, [5] H & D curves, [6] D–logE curves, [7] or D–logH curves. [8] At moderate exposures, the overall shape is typically a bit like an "S" slanted so that its base and top are ...
The two-dimensional measures above find one-dimensional counterparts in straightness measures, [5] defined by ISO 12780 on a cross-section (the plane curve resulting from the intersection of the surface of interest and a plane spanned by the surface normal): least squares reference line; minimum zone reference lines; local straightness deviation