Truncated translating contact lens with optimized performance and method of design
Translating contact lenses which are truncated for correcting presbyopia and whose design is optimized to maximize translation ability while maintaining comfort when the lens is worn on eye. Truncation of the lenses results in a non-round geometry while still retaining under-lid residency in select portions of the lens itself. Maximum thickness and back surface radius of curvature along with ramp shape can be optimized individually or in combination to maximize translation of the lens relative to the eye, when the lens is positioned on eye.
1. A method of designing a contact lens with an anterior and a posterior surface having a variable thickness variation of 0.3 mm or less comprising: selecting one or more optimizable lens parameters in order to maximize lens translation on eye, wherein said one or more optimizable lens parameters is selected from the group consisting of a maximum lens thickness, a back curve radius of curvature having both a minimum and maximum radius of curvature, and a ramp shape; for each of said one or more optimizable lens parameters determining the value of that parameter at both an inferior and a superior position relative to a horizontal meridian passing through a geometric center of the contact lens along a vertical meridian passing through the geometric center of the contact lens; for each of said one or more optimizable lens parameters determining the value of that parameter at the medial and lateral positions along the horizontal meridian; selecting the values for each of said one or more optimizable lens parameters along intervening locations between positions that result in a smooth and continuous geometry; and fabricating a contact lens having a variable thickness of 0.3 mm or less, having a variation in back curve radius wherein the radius of curvature of the back curve radius of the posterior surface in the superior region is larger that of the radius of curvature of the back curve radius of the posterior surface in the inferior region and the value of this variation is 0.4 mm or greater, having a ramp shape with a thickness wherein said ramp shape is selected from the group consisting of either concave, convex or linear on the anterior surface and the thickness of the ramp shape is thickest at the inferior position of the lens.