PAIR OF PROGRESSIVE OPHTHAMLIC LENSES

摘要

A pair of progressive ophthalmic lenses (1, 2) meets special conditions for improving binocular vision of a wearer, while avoiding discomfort for peripheral vision. A first one of the conditions relates to width values of far vision fields and/or proximate vision fields, for indicating that the fields are different enough in width between both lenses. A second one of the conditions sets a maximum value for the relative difference in mean refractive power gradient between both lenses.

主权项

1. A pair of progressive ophthalmic lenses (1, 2), wherein
each lens has a prescribed addition ADD which is common to both lenses of the pair and, in as-worn conditions of the lens by a wearer, a meridian line (ML), a nasal side (N) and a temporal side (T) on either side of the meridian line, respectively, a fitting cross (FC), a prism reference point (PRP), a proximate vision gaze direction (GVP), a mean refractive power PPOα, β and a module of resulting astigmatism ASRα, β for each gaze direction (G) through the lens and corresponding to a lowering angle α and an azimuth angle β relating to a cyclopean coordinate system, said cyclopean coordinate system being defined for a separation distance equal to 64 mm between both pupils of a wearer of the lenses, and for a cyclopean eye located at mid position between both wearer's eyes, a mean refractive power deviation DPPOα, β being defined for each gaze direction (G) as follows, separately for each lens:
DPPOα, β=PPOα, β−PPOα, βmeridian, where PPOα, βmeridian is the mean refractive power on the meridian line (ML) for the same value of the lowering angle α as that of the gaze direction, a total deviation Pα, β being further defined for each gaze direction (G) as follows, separately for each lens:
Pα, βm*(DPPOα, β)a+n*(ASRα, β)b, where m, n, a and b are parameters such that m≧0, n≧0, (m, n)≠(0, 0), 0a first width value (H_OR_VL, H_OL_VL) defined as an angular distance between first (G1) and second (G2) gaze directions respectively on the nasal and temporal sides of the lens, both first and second gaze directions with lowering angle (a) equal to that of a gaze direction (GFC) through the fitting cross, and each where the total deviation Pα, β satisfies:
Pα, β=m*(ADD/8)a+n*(ADD/4)b; and a second width value (H_OR_VP, H_OL_VP) defined as an angular distance between third (G3) and fourth (G4) gaze directions respectively on the nasal and temporal sides of the lens, both third and fourth gaze directions with lowering angle (α) equal to that of the proximate vision gaze direction (GVP), and each where the total deviation Pα, β satisfies:
Pα, β=m*(ADD/4)a+n*(ADD/2)b, wherein the pair of lenses (1, 2) has a total horizontal width ratio defined as a relative difference between the respective first width values of both lenses (H_OR_VL, H_OL_VL) of the pair, or between the respective second width values of both lenses (H_OR_VP, H_OL_VP) of the pair, greater than or equal to 0.10 in absolute value, the relative difference between two values being a ratio of a difference between said values over a sum of said values; and wherein each lens (1, 2) separately further has a maximum mean refractive power gradient produced for a gaze direction (G) corresponding to a cyclopean gaze direction which is comprised:
inside a zone centered at the cyclopean gaze direction corresponding to gaze direction (GRRP) passing through the prism reference point (PRP) and containing all cyclopean gaze directions (α, β) respecting the following inequality (|α|2+|β|2)1/2≦40°, andoutside a central optical zone; the central optical zone comprising a main line (ML_min (αmin, βmin)) of cyclopean directions for which, for each angle αmin, the resulting astigmatism reaches its minimum, the central optical zone being delimited on either side of the main line by cyclopean gaze directions whose azimuth angle is equal to βmin±5°, and a relative difference in the maximum mean refractive power gradient between both lenses (1, 2) of the pair is less than or equal to 0.08 in absolute value.