| CPC G02C 7/047 (2013.01) | 15 Claims |
|
1. An orthokeratology contact lens for correcting and slowing progression of myopia by reshaping a portion of the cornea of a myopic eye;
the lens having a posterior surface for contacting with the portion of cornea to be reshaped, wherein the posterior surface comprises:
a correction region for reducing the curvature of a central portion of the cornea, the correction region being defined by a first section of the posterior surface having a radius of curvature;
an annular treatment recess for inducing myopic defocus in a peripheral portion of the cornea, wherein the annular treatment recess extends radially outwards from a perimeter of the correction region and is defined by a second section of the posterior surface having a radius of curvature less than the radius of curvature of the first section, and wherein the radius of curvature of the second section is such that the annular treatment recess is configured to induce a myopic defocus of at least +1 D in the peripheral portion of the cornea and less than +12 D in the peripheral portion of the cornea; and,
a regulating region for regulating the myopic defocus induced by the annular treatment recess, wherein the regulating region extends radially outwards from a perimeter of the annular treatment recess and is defined by a third section of posterior surface having a radius of curvature;
wherein the orthokeratology lens is according to (i) or (ii), wherein:
(i) the radius of curvature of the first section of the posterior surface of the lens defining the correction region is in the range from 8.8 mm to 9.3 mm; and,
the radius of curvature of the second section of the posterior surface of the lens defining the annular treatment recess is in the range from 8.3 mm to 8.8 mm, provided the radius of curvature of the second section is less than the radius of curvature of the first section of the posterior surface;
the radius of curvature of the third section of the posterior surface of the lens defining the regulating region is in the range from 7.9 mm to 8.4 mm provided the radius of curvature of the third section is less than the radius of curvature of the first section of the posterior surface; and
wherein the radius of curvature of the third section of the posterior surface is less than the radius of curvature of the second section of the posterior surface;
(ii) the radius of curvature of the first section of the posterior surface of the lens defining the correction region is in the range from 7 mm to 9.5 mm; and,
the radius of curvature of the second section of the posterior surface of the lens defining the annular treatment recess is in the range from 5.5 mm to 8.5 mm, provided the radius of curvature of the second section is less than the radius of curvature of the first section; and,
the radius of curvature of the third section of the posterior surface of the lens defining the regulating region is in the range from 7.0 mm to 15.0 mm, wherein the radius of curvature of the third section is greater than the radius of curvature of the second section defining the annular treatment recess; and,
wherein the radius of curvature of the regulating region is greater than the radius of curvature of the correction region.
|