Title of Invention

A METHOD FOR DESIGNING AN OPTHALMIC LENS

Abstract A method for designing an ophthalmic tens comprising the steps of: generating a thickness map for at least a portion of the periphery of the lens by the steps comprising; i.) describing at least a portion of the lens periphery using a plurality of parallels and meridians to define a coarse mesh; recording intersection points of the parallels and meridians as one of Cartesian, cylindrical, or spherical coordinates; and iii.) defining a thickness variation for each of the plurality of parallels; and calculating a thickness for each intersection point; and b.) deriving a geometry for at least a portion of the lens periphery from the thickness map.
Full Text METHOD FOR DESIGNING CONTACT LENSES
Field of the Invention
The invention relates to methods for designing contact lenses. In particular,
the invention provides a method for designing contact lenses in which the thickness
in the lens periphery is precisely controlled.
Background of the Invention
The use of contact lenses for purposes of visual acuity correction and
cosmetics is well known. It is important in the design of a contact lens to provide
for good handling, comfort, centration, and orientation of the lens. Each of these
lens characteristics is dependent to a large extent on the thickness profile of the lens
periphery.
Conventional methods for controlling the thickness of the lens periphery
include the use of one or more of lenticular zones, bevels, chamfers, and the like.
However, these methods do not provide precise control of the thickness differential
of the lens periphery. Additionally, these methods do not provide a means for
designing a non-rotationally symmetric lens. Therefore, a need exists for a method
for designing contact lenses that overcomes these disadvantages.
Brief Description of the Drawings
**—■
Fig. 1 is a depiction of a coarse mesh used in the method of the invention.
Fig. 2 is a graph of the thickness variations of several parallels of Fig. 1.
Fig. 3 is a depiction of intersection points of the mesh of Fig. 1 and a point
falling between the parallels and meridians of that mesh.
Fig. 4 is a graph for use in the method of the invention.

Detailed Description of the Invention and Preferred Embodiments
The invention provides a method, and lenses produced using the method, for
designing articles, preferably ophthalmic lenses, in which the thickness of the
periphery may be precisely controlled. Thus, the method provides for precise
control of the thickness differential of the periphery and the location of the
differential on the periphery. Finally, the method provides a ready means for
designing non-rotationally symmetric articles.
In a preferred embodiment, the invention provides a method for designing an
ophthalmic lens, the method comprising, consisting essentially of, and consisting of:
a.) generating a thickness map for at least a portion of the periphery of the lens; and
b.) deriving a geometry for at least a portion of the lens periphery from the thickness
map. In another preferred embodiment, the invention provides an ophthalmic lens
produced by this method.
By "ophthalmic lens" is meant a spectacle lens, contact lens, intraocular lens,
onlay lens, or the like. Preferably, the lens designed using the method of the
invention is a contact lens. For purposes of the invention, by "lens periphery" or
"periphery of the lens" is meant the portion of the lens that is outside of the optic
zone.
For the lens of the invention, the optical properties of its base curve and
optical zones may be designed in any conventional manner. The base curve and
optical curve may be described in any manner, as long as for a given diameter D on
the base curve, the corresponding sag value S may be derived.

In a preferred method, at least a portion of, and preferably all of, the lens
periphery is first described using parallels and meridians, as shown in Fig. 1, to
define a coarse mesh. The location of all of the intersecting points of the mesh are
recorded as Cartesian, cylindrical, or spherical coordinates and stored in arrays. The
greater the number of points used, the greater will be the precision for controlling
the lens periphery thickness.
Further, the intersecting points are divided into at least three families of
arrays: optic zone array points that are located at the innermost border of the
periphery; exterior array points that are located at the outermost border of the
periphery; and mid-array points that are located between the inner and outermost
array points. In Fig. 1 is depicted representative members of each of these arrays.
The thickness differential or, preferably, the thickness variation then is
defined for each parallel of the mesh. Preferably, this is carried out by one of two
methods. First, a set of functions may be used to define the thickness variation
along each parallel. The variations may be a function of any or all of the Cartesian,
cylindrical, and spherical functions. For example, the variation may be a function of
the angle of rotation 6. Referring to Fig. 2, the lens thickness along three parallels is
shown. The function may be of any form. Preferably, the function is selected so
that it creates a smooth surface, provides the means for creating non-axisymmetric
lenses with thin zones for better centering, and is reasonably easy to visualize.
Suitable functions include, without limitation, functions of the following form
Lens Thickness = A*Cos(θ) + B
Lens Thickness = A*Cos(Bθ + C) + D, wherein A is the
maximum thickness differential in each parallel and D is the thickness at 0 - 90°
Lens Thickness = A*Cos2(B. θ + C) + D*Sin2(E.θ + C)

Lens Thickness = A*|Cos(B. θ+C|+D, for θ = [0, Pi]
Lens Thickness =A*(1+|Sinθ|), for θ = ]Pi, 2.Pi[
The number of functions that need to be defined are equal to Nr, or the
number of parallels. One ordinarily skilled in the art will recognize that, in addition
to trigonometric functions, any suitable function may be used including, without
limitation, exponential, series, logarithmic, polynomial, step functions, and the like.
Preferably, trigonometric functions are used and more preferably trigonometric
functions are used in conjunction with step functions. Alternatively, the thickness
variations may be defined manually at every point. In this method, the thickness of
the lens at every point is specified. However, this method is disadvantageous
because it is cumbersome. The resulting thickness for each intersection point, the
number of points which equals Nr*Nθ wherein Nθ is the number of meridians, is
calculated and recorded.
In the second step of the method, a geometry of the lens periphery is derived
from the thickness map. This step is carried out by first refining the coarse mesh to
the desired accuracy in order to define the lens periphery more precisely. The
refined, or fine, mesh describes the same lens geometry, but uses a greater number
of points than does the coarse mesh. For example, referring to Fig. 1, the coarse
mesh has Nr*N0 intersection points, or 60. In the fine mesh, there may be, for
example, 3600 points. The precise number of points used will be determined by
balancing the use of as many points as possible to obtain a better lens definition
against the computation time and storage space required for the information along
with the fact that the lathes used to cut the tools for the lens may not be able to cut
with the level of accuracy necessary for a large number of points.
The thickness and coordinates of the coarse mesh points are used to derive
the thickness and z coordinates of the fine mesh points. For fine mesh points located

on one of the parallels, the function corresponding to the parallel is used to derive
the thickness of that point. For fine mesh points falling on one of the meridians, an
approximation is used to derive the lens thickness. Suitable approximations may be
made by selecting a function type and from that function type, deriving the curve
that best fits the data points. Examples of useful function types include, without
limitation, polynomial function, conic functions, exponential functions, rational
functions, logarithmic functions, trigonometric functions, and the like. Additionally
and preferably, cubic spline approximations, or a series of special polynomials, may
be used.
In the case of a fine mesh point that falls between the meridians and
parallels, adjacent points falling on the parallels and meridians may be used to
determine the fine mesh point's properties. Referring to Fig. 3, points nl through n4
are shown along with fine mesh point P. The distance between Nl through n4 to
point P is dl, d2, d3, and d4, respectively. The thickness at point P may be
calculated by any suitable method including, without limitation, the use of bilinear
interpolation, bicubic interpolation, bicubic splines, and the like. A quick, but crude
method is as follows:
T(P) = (wl*T(nl) + w2*T(n2) + w3*T(n3) + w4*T(n4)
wherein T is thickness and where SumD = dl + d2 + d3 + d4, and
wl = [1-dl/SumD]/3
w2 = [1-d2/SumD]/3
w3 = [l-d3/SumD]/3
w4 = [l-d4/SumD]/3
Alternatively, a three-dimensional cubic spline approximation may be used
to approximate the location of the fine mesh points. Three-dimensional cubic spline

approximations and their use are described in Numerical Recipes in Fortran 77: The
Art of Scientific Computing, Cambridge Press (1996)
Once the thickness is calculated for all of fine mesh points, the z coordinates
(or p for spherical coordinates) may be derived. Referring to Fig. 4, an example for
a spherical base curve zone is shown. In Fig. 4, Pf(Zf, Rf) is the point on the front
surface for which the z coordinate is to be derived, Rbc is the base curve radius, and
(Zctr, Rctr) are the coordinates of the center of the base curve and Thck is the
thickness at Pf Zf is found using the following formula:

In the case in which the base curve is non-spherical, the procedure may be
more complicated, but may be summarized as follows: a.) offset the base curve by
Thck; b.) intersect the offset curve with line r = Rf, wherein r = Rf is an equation
for a line containing all of the points with y-coordinate Rf in a Cartesian coordinate
system; and c.) select the correct solution if there are more than one solutions. One
ordinarily skilled in the art will recognize that the correct solution will depend on
the form of the equation of the offset curve.
In this way, all or a portion of the geometry of the lens periphery may be
fully described as a point cloud. The lens periphery designed according to the
method of the invention may be used in the design of any type of ophthalmic lens,
but preferably is used in designing contact lenses and more preferably contact lens
that are spherical, multifocal, toric, or combinations thereof. However, the method
may find its greatest utility in the design of toric contact lenses.

We Claim:
1. A method for designing an ophthalmic lens comprising the steps
of:
a) generating a thickness map for at least a portion of the
periphery of the lens by the steps comprising:
i) describing at least a portion of the lens periphery using a
plurality of parallels and meridians to define a coarse mesh;
ii) recording intersection points of the parallels and meridians as
one of Cartesian, cylindrical, or spherical coordinates; and
iii)defining a thickness variation for each of the plurality of
parallels; and calculating a thickness for each intersection point;
and b) deriving a geometry for at least a portion of the lens
periphery from the thickness map.
2. The method as claimed in claim 1, wherein the lens is a contact
lens.
3. The method as claimed in claim 2, wherein the lens is a non-
rotationally symmetric lens.
4. The method as claimed in claim 2, wherein step b) further
comprises refining the coarse mesh by deriving a coordinates and
thickness for a plurality of points in addition to the intersection
points of the coarse mesh.

5. The method as claimed in claim 1, wherein substep iii) is carried
out by defining a thickness variation using a function selected from
the group consisting of trigonometric, exponential, series,
logarithmic, polynomial, and step functions, and combinations
thereof.
6. The method as claimed in claim 1, wherein substep iii) is carried
out by defining a thickness variation using a trigonometric
function.
7. The method as claimed in claim 1, wherein substep iii) is carried
out by defining a thickness variation using a trigonometric function
and a step function.
8. The method as claimed in claim 4, wherein in step b) the
coordinates are derived using the formula:

wherein Rbc is a base curve radius, Zctr and Rctr are the
coordinates of the center of the base curve, Thck is the thickness at
the point on the front surface for which the coordinates is to be
derived.

9. The method as claimed in claim 4, wherein step b) further
comprises:
i) offsetting a base curve by a thickness at a point on a surface for
which the coordinates are to be derived;
ii) intersecting the offset base curve with a line; and
iii) selecting a solution.
10. The method as claimed in claim 4, wherein step b) is carried out by
approximating locations for the fine mesh points using a three-
dimensional cubic spline approximation.
11. An ophthalmic lens designed according to the method as claimed
in claim 1.
12. An ophthalmic lens designed according to the method as claimed
in claim 2.
13. An ophthalmic lens as designed by the method as claimed in the
preceeding claims is a non-rotationally symmetric contact lens.

A method for designing an ophthalmic tens comprising the steps of:
a.) generating a thickness map for at least a portion of the periphery
of the lens by the steps comprising; i.) describing at least a portion of
the lens periphery using a plurality of parallels and meridians to
define a coarse mesh; ii.) recording intersection points of the
parallels and meridians as one of Cartesian, cylindrical, or spherical
coordinates; and iii.) defining a thickness variation for each of the
plurality of parallels; and calculating a thickness for each intersection
point; and b.) deriving a geometry for at least a portion of the lens
periphery from the thickness map.

Documents:

610-KOLNP-2003-FORM-27.pdf

610-kolnp-2003-granted-abstract.pdf

610-kolnp-2003-granted-assignment.pdf

610-kolnp-2003-granted-claims.pdf

610-kolnp-2003-granted-correspondence.pdf

610-kolnp-2003-granted-description (complete).pdf

610-kolnp-2003-granted-drawings.pdf

610-kolnp-2003-granted-examination report.pdf

610-kolnp-2003-granted-form 1.pdf

610-kolnp-2003-granted-form 18.pdf

610-kolnp-2003-granted-form 2.pdf

610-kolnp-2003-granted-form 3.pdf

610-kolnp-2003-granted-form 5.pdf

610-kolnp-2003-granted-reply to examination report.pdf

610-kolnp-2003-granted-specification.pdf

610-kolnp-2003-granted-translated copy of priority document.pdf


Patent Number 227615
Indian Patent Application Number 610/KOLNP/2003
PG Journal Number 03/2009
Publication Date 16-Jan-2009
Grant Date 14-Jan-2009
Date of Filing 13-May-2003
Name of Patentee JOHNSON & JOHNSON VISION CARE, INC.
Applicant Address 7500 CENTURION PARKWAY, SUITE 100, JACKSONVILLE, FL 32256
Inventors:
# Inventor's Name Inventor's Address
1 JUBIN PHILIPPE 5407 STETSON ROAD, JACKSONVILLE, FL 32207
PCT International Classification Number G02C 7/04
PCT International Application Number PCT/US01/47090
PCT International Filing date 2001-11-13
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA