TH18364B - Progressive multifocal contact lenses are suitable for correcting farsightedness. - Google Patents

Abstract

DC60 (23/02/42) The optical power progression of a lens consists of a first stage (a) which rapidly decreases to the base refractive power and in which the lens acts for nearsightedness; a second, nearsighted stage (b) which remains at the level of the true base refractive power and in which the lens acts for farsightedness; and a third stage (c) which consists of a first progressively increasing section (c') and a second fixed section (c'') in which the lens acts progressively for intermediate distances in the first stage and in a fixed manner for nearsightedness in the second stage (Figure 2). The optical power progression of a lens consists of a first stage (a) which rapidly decreases to the base refractive power and in which the lens acts for nearsightedness; a second, nearsighted stage (b) which remains at the level of the true base refractive power and in which the lens acts for farsightedness; and a third stage (c) which consists of a first progressively increasing section (c') and a second fixed section (c'') in which the lens acts progressively for intermediate distances in the first stage. And in a constant manner for nearsightedness in the second part (Figure 2).

Claims (3)

1. A progressive multifocal contact lens (1) suitable for compensating hyperopia, which is characterized by the power of the optical zone varying continuously with the base refractive power between the center of the lens and the periphery of the optical zone, according to the progression shown as the central peak value, from which the first segment (a) is deflected by rapidly decreasing to the base refractive power, and along this direction the lens acts for the intermediate second myopia (b) parallel to the horizontal coordinate at the base refractive power value, and along this direction the lens acts for the peripheral third myopia (c) consisting of a first progressively increasing segment (c') and a second segment (c'') parallel to the horizontal coordinate, in which these two segments (c', c'') correspond to the power to which the lens acts progressively for the intermediate distance in the first segment and in a constant manner for the myopia in the second segment. 2. Progressive multifocal contact lenses, according to claim 1, are characterized as follows: - The first segment (a) has a vertex at the center of the lens, which rises to approximately 6 refractive powers, from which it is typically reduced to a value of 0 refractive powers, equivalent to the base refractive power, at a distance from the center of the lens which may range from 0.5 to 1.5 mm. - The second segment (b) is parallel to the horizontal coordinate at the level of 0 refractive powers and remains virtually constant from the lowest point of the first segment (a) to a point corresponding to the lower end of the third segment (c). - The third segment (c) consists of i) the first segment (c') which rises progressively from the aforementioned corresponding point to a point positioned at a distance from the center of the lens between 2.5 and 1.5 mm. 3.5 mm and with a refractive power consisting of between 0.5 and 5.0 ii) the second part (c") which will remain truly constant at such values of refractive power consisting of a distance of 0.5 and 5.0 for all remaining extensions of the optical zone of the lens from the aforementioned distances from the center of the lens between 2.5 and 3.5 mm, directly through to the circumference of the optical zone.