Progressive multifocal ophthalmic lens
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United States of America Patent
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-
Dec 21, 1993
Grant Date -
N/A
app pub date -
Oct 28, 1992
filing date -
Nov 12, 1991
priority date (Note) -
In Force
status (Latency Note)
Importance
Abstract
The lens has an aspherical surface having a zone for far vision, a zone for near vision, and between these two zones, a zone for intermediate vision, with a meridian curve along which the curvature of the surface varies progressively and which is inclined from top to bottom towards the nose side of the lens, at least in the intermediate zone. The portion of the meridian curve situated in the intermediate and near zones includes a segment at an angle .alpha. to the vertical where the value of .alpha. is an increasing function of the power addition A of the lens. In a horizontal and vertical system of coordinates, a point of the segment has an ordinate whose value is also an increasing function of the power addition A. At said point, the mean sphere value of the surface corresponds to a power addition lying in the range 0.8 to 0.92 times the nominal power addition of the lens.
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