| 摘要 |
PROBLEM TO BE SOLVED: To obtain a lens by which a presbyopic person can turn his (her) line of sight on the original position of a short-distance object when he (she) views a short range and he (she) is not fatigued even when he (she) continues to view the short range for a long time by setting the horizontal component of prism refractive power at a nearsighted part prism measuring reference point to 0Δ(prism). SOLUTION: A farsighted part prism measuring reference point exists at the lower end of a farsighted part area, and the nearsighted part prism measuring reference point 22 exists at the upper end of a nearsighted part area. In this progressive multifocus lens, the farsighted part prism measuring reference point and the point 22 correspond to a farsighted part design reference point and a nearsighted part design reference point, respectively. In the lens, an object side refractive surface 31 is rotated around a rotary shaft perpendicular to a drawing on a nearsighted part horizontal cross section shown in a figure so as to make the horizontal component of the prism refractive power 0Δ(prism) at the point 22. Therefore, the presbyopic person views the short-distance object by turning his (her) line of sight in the same direction as in the case of viewing with naked eyes like the line of sight shown by a solid line.
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