Patent ID: 6533416
Filing Date: 2003-03-18
Classification: A61F,G02C

Abstract:
Contact or intraocular lens comprising a correcting portion (5) in order to correct the vision of a possibly myopic or hyperopic and/or possibly presbyopic astigmatic eye, comprising an optical axis (2) and a reference meridian (8); characterized in that it introduces, for correction of only the astigmatism, an optical path varying as a function of the distance (h) with regard to the optical axis (2) and as a function of the angular separation (&thgr;) with regard to the reference meridian (8), at least when this distance is between 0.4 mm and 2.4 mm, according to the following equation:&dgr;A(h,&thgr;)=&dgr;toric(h,&thgr;)+&dgr;atoric(h,&thgr;) in which equation:&dgr;toric(h,&thgr;) is a cylindrical optical path (13,26) which satisfies, according to the parabolic approximation, the expression &dgr;toric(h,&thgr;)=C/2 h2 sin2(&thgr;âˆ’&phgr;), where &phgr; is the axis required in order to correct the astigmatism of said eye expressed in angular separation with regard to said reference meridian, and where C is the cylinder value required in order to correct the astigmatism of said eye; and &dgr;toric(h,&thgr;) is an optical path (29,30), such that when h is a constant, it varies as a function of &thgr; with a 2&pgr; period, and differently from sin2(&thgr;âˆ’&phgr;), this optical path in addition satisfies the condition: &Dgr;&phgr;â€²&gE;1.3 &Dgr;&phgr;in which inequation: &Dgr;&phgr;is the amplitude of the range of variation [âˆ’Â½&Dgr;&phgr;, Â½&Dgr;&phgr;] of a variable x, amplitude such that for any value of x taken in this interval, the following condition is verified: MTFa&af;[Î´toric&it;â€ƒ&it;(h,Î¸-x)-Î´toric&it;â€ƒ&it;(h,Î¸)]&GreaterEqual;MTFa&it;â€ƒ&it;[0.25&it;â€ƒ&it;h2]2&Dgr;&phgr;â€² is the amplitude of the range of variation [âˆ’Â½&Dgr;&phgr;â€², Â½&Dgr;&phgr;â€²] of a variable x, amplitude such that for any value of x taken in this interval, the following condition is verified: MTFa&af;[Î´A&it;â€ƒ&it;(h,Î¸-x)-Î´toric&it;â€ƒ&it;(h,Î¸)]&GreaterEqual;MTFa&it;â€ƒ&it;[0.25&it;â€ƒ&it;h2]2the notation MTFa[f(h,&thgr;)] designating, for an optical path f(h,&thgr;), the criterion of optic quality calculated from the modulation transfer function produced by this optical path for a predetermined pupil diameter between 4 and 7 mm according to the formula: MTFa&af;[f&it;â€ƒ&it;(h,Î¸)]=&Integral;v=5v=15&it;&Integral;x=0x=360&it;MTF360&it;â€ƒ[f&it;â€ƒ&it;(h,Î¸)]&it;â€ƒ&it;(v,Ï‡)&it;â€ƒ&it;&PartialD;v&it;&PartialD;Ï‡&it;â€ƒin which formula &ngr; and &khgr; are the polar coordinates in the plane of the angular spatial frequencies, being expressed in cycles per degree and &khgr; in degrees; and in which MTF[f(h,&thgr;)](,&khgr;) is the modulation transfer function of the optical path f(h,&thgr;) according to said polar coordinates.