Different zones in a progressive lens and relevant reference points.

Contexts in source publication

Context 1

... is not rotationally symmetrical, with continuous change of focal power over a part or the whole of the lens [15]. In other words a progressive lens is a lens with a progressive surface (progressive side), with a continuous change of curvature over a part or whole of the surface [15]. In a progressive lens we can identify different zone [15,16] ( fig. 1): - a distance portion having the dioptric power for the distance vision, - a near portion or reading portion having the dioptric power for the near vision, - an intermediate corridor that provides clear vision for ranges intermediate between distance and near, - two blending regions that flanked to either side the other portions, ...

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... ISO standard limit, that are defined for the progressive surface [36] and for the complete lens [37] as a function of the nominal power and astigmatic power in the reference point for distance and near vision. This limit is defined only to the design reference points for far and near vision, but no one prescription is defined for the corridor ( fig. 1). In this regard an interesting method is proposed by Sheedy [32][33][34][35] and it is adopted to compare different progressive lens design. This studies show that actual progressive additional lens are connected to a specific design in which the amplitude of the distance and the near vision portion is ...

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... box ( fig. 9 c). Therefore the parameters for the data exchange can be set as in fig. 9 Following the procedure described, the plug-in computes shape and optical properties which can be visualized as 3D mesh. Moreover the relevant files in *.hmf and *.xyz format are performed and exported in a folder named C:\Progressive for the CNC machining. In fig. 10 an example of the results is shown where iso- astigmatic and iso-power contour lines every 0.50 D are emphasized in the top view, while the shape of the lens (front surface and back surface), astigmatic surface power (cylinder map) and surface power (power map) are highlighted as mesh in the perspective view. Astigmatism and power map ...

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... assess the performance of the method eight geometric models, derived by the parameters in tab. 5, are analyzed with the virtual tools described in 2.3: fig. 11 illustrates the curvature and the relevant derivative trend along the corridor, fig. 12 shows the astigmatic surface power and the surface power, while tab. 6 reports the maximum value of the astigmatic surface power at the left and at the right of the corridor near the x axis and the surface power in the distance vision portion and in ...

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... assess the performance of the method eight geometric models, derived by the parameters in tab. 5, are analyzed with the virtual tools described in 2.3: fig. 11 illustrates the curvature and the relevant derivative trend along the corridor, fig. 12 shows the astigmatic surface power and the surface power, while tab. 6 reports the maximum value of the astigmatic surface power at the left and at the right of the corridor near the x axis and the surface power in the distance vision portion and in the near vision area. In these test cases the influence of the approach for drawing the ...

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... fig. 12 b) together to fig. 12 g), in which the only the addition of the lens is changed, a proportional variation in the astigmatism map has been found. Same considerations can be drawn from tab. 6: the ratio between the maximum surface astigmatism is equal to the ratio between the addition (test cases b), ...

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... fig. 12 b) together to fig. 12 g), in which the only the addition of the lens is changed, a proportional variation in the astigmatism map has been found. Same considerations can be drawn from tab. 6: the ratio between the maximum surface astigmatism is equal to the ratio between the addition (test cases b), ...

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... Comparing fig. 12 b) together to fig. 12 h), in which the only the power of the lens is changed, it was observed that no significant change in astigmatism map has been found. Moreover in tab. 6 the same value of the maximum surface astigmatism can be found for the test cases b), ...

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... Comparing fig. 12 b) together to fig. 12 h), in which the only the power of the lens is changed, it was observed that no significant change in astigmatism map has been found. Moreover in tab. 6 the same value of the maximum surface astigmatism can be found for the test cases b), ...