A process for determining a pair of progressive ophthalmic lenses

摘要

The process comprises: determining prescribed far vision mean power and addition for each lens of the pair; determining laterality of a wearer; defining a temporal side and a nasal side on each lens of the pair; defining, on each lens being worn and for each gaze direction, a refractive power and a module of resulting astigmatism, each gaze direction corresponding to a lowering angle and to an azimuth angle; defining a proximate vision gaze direction for each lens of the pair; defining, for each lens of the pair, a temporal half-width field of refractive power as the angular distance, at constant lowering angle, between the proximate vision gaze direction and a gaze direction on the temporal side of the lens where the refractive power reaches the value of the prescribed far vision mean power plus three quarters of the prescribed addition; defining, for each lens of the pair, a nasal half-width field of refractive power as the angular distance, at constant lowering angle, between the proximate vision gaze direction and a gaze direction on the nasal side of the lens where the refractive power reaches the value of the prescribed far vision mean power plus three quarters of the prescribed addition; defining, for each lens of the pair, a temporal half-width field of module of resulting astigmatism as the angular distance, at constant lowering angle, between the proximate vision gaze direction and a gaze direction on the temporal side of the lens where the module of resulting astigmatism reaches the value of one quarter of the prescribed addition; and defining, for each lens of the pair, a nasal half-width field of module of resulting astigmatism as the angular distance, at constant lowering angle, between the proximate vision gaze direction and a gaze direction on the nasal side of the lens where the module of resulting astigmatism reaches the value of one quarter of the prescribed addition. The ratio of the difference over the sum of temporal and nasal half-width fields of refractive power and/or the ratio of the difference over the sum of temporal and nasal half-width fields of module of resulting astigmatism are determined for each lens of the pair based on the laterality of the wearer.