Patent Description:
Contact lenses are generally cast molded by depositing a curable liquid into a mold cavity defined by two mold halves. The liquid is then cured within the mold cavity. Following the curing process the cured lenses are removed from the mold cavity. The lenses will then typically move through other post curing steps to produce a finished lens. The anterior mold half defines the anterior surface of the lens. The posterior mold half defines the posterior surface of the lens. Mold halves are traditionally used only once and then serve as an element of the packaging for the finished lenses or are discarded. In order to manufacture contact lens mold halves of a desired radius or power, posterior and anterior step tools are used to produce a batch of baseline molds. The baseline molds are measured for accuracy, and a series of step changes must then be made until the desired dimensions are achieved in the resulting mold halves.

The desired final lens product determines the design of the necessary posterior and anterior mold halves. More specifically, the final lens product design determines the portion of the mold that forms the optic surface. The desired mold determines the specific step tools. Conventional design procedures dictate that the desired base curve of the lens determines the design of the posterior mold. The desired optical characteristics of the lens typically determines the anterior design of the lens and the corresponding mold half. Accordingly, each lens that requires a different power, different curvature, or different optical characteristics will also require a different set of posterior and anterior mold halves. Due to the number of different factors considered in each lens design, the number of required posterior and anterior mold halves to accommodate each lens design can be significant.

For example, the hydrogel contact lens is usually available in power of <NUM> diopter increments. Each time a different power lens is produced, a corresponding anterior mold type is used. In this scenario, only one posterior mold type is used throughout the power range. A contact lens series having powers from -<NUM> D to -<NUM> D in <NUM> D increments has <NUM> different lens types. Accordingly, there is a need to reduce the number of required posterior and anterior molds to reduce costs and complexities associated with contact lens production.

Application <CIT> discloses a series of aspherical contact lenses, each lens having a first central optical zone on its anterior surface and a second central optical zone on its posterior surface. Both central optical zones are aspherical surfaces. The first central optical zone is designed to have a surface which provides a target optical power and an optical power profile selected from the group consisting of (<NUM>) a substantially constant optical power profile, (<NUM>) a power profile mimicking the optical power profile of a spherical lens with an identical targeted optical power, and (<NUM>) a power profile in which lens spherical aberration at <NUM> diameter is from about <NUM> diopter to about <NUM> diopters more negative than spherical aberration at <NUM> diameter.

<CIT> discloses a method for forming a set of contact lenses and a set of moulds for forming a set of contact lenses.

In view of the foregoing, it is an object of the present disclosure to provide a method and apparatus for forming contact lenses.

The present invention relates to a method for forming contact lenses according to claim <NUM> and to an apparatus for forming contact lenses according to claim <NUM>.

The following will describe embodiments of the present disclosure, but it should be appreciated that the present disclosure is not limited to the described embodiments and various modifications of the invention are possible without departing from the basic principles. The scope of the present disclosure is therefore to be determined solely by the appended claims.

The optical power imparted by a contact lens is based on the relationship between the radii of the front surface (the anterior surface) and the on-eye or rear surface (the posterior surface). These two surfaces of a contact lens are formed by plastic molds produced from anterior and posterior optical tooling in a matrix combination. In other words, a collection of posterior and anterior mold halves that can produce a given contact lens having certain properties (e.g., power) can be represented by a matrix array with anterior molds on one axis and posterior molds on an adjacent axis. The combination of the mold halves produce a contact lens having specific properties.

Referring to <FIG>, shown is a perspective exploded view of a mold a posterior and anterior mold assembly with a contact lens molded therein. Shown in <FIG> is a posterior mold and anterior mold assembly <NUM>. Assembly <NUM> includes an anterior mold <NUM> having an anterior optic defining surface <NUM>, and posterior mold <NUM> having a posterior mold optic defining surface <NUM>. Also shown in <FIG> is contact lens <NUM>. Embodiments of contact lens <NUM> include an ophthalmic lens, such as a toric lens. In order to form contact lens <NUM>, a curable liquid, which is preferably a polymerizable monomer mix, is introduced to the anterior mold optic defining surface <NUM>. The two molds are brought into association with each other and the mix is at least partially cured forming contact lens <NUM>.

Referring now to <FIG>, shown is a cross-sectional view of the exemplary posterior and anterior mold assembly. Shown in <FIG> is anterior mold <NUM> having an anterior optic defining surface <NUM>, posterior mold <NUM> having posterior mold optic defining surface <NUM>, and mold cavity <NUM>. The posterior mold <NUM> and the anterior mold <NUM> have surface characteristics that are present on surface <NUM> and surface <NUM>. These surface characteristics are transferred to the respective anterior and posterior surfaces of the molded contact lens and define the specifications of the resultant contact lens. Some of these surface characteristics include lens radius, shape, and conic. Accordingly, a given anterior mold <NUM> and posterior mold <NUM> are only operable to produce a lens with certain properties such as power. Thus, many different posterior and anterior molds are required in order to manufacture many different lenses with different characteristics.

The tooling to construct the many different posterior and anterior mold halves (including the optic defining surfaces of each mold) can be arranged in a matrix that allows a given posterior tool to be matched with a range of anterior tooling. For example, <FIG> illustrates an exemplary matrix with different anterior and posterior tools that can produce an array of molds and lenses with different optical characteristics. As shown in <FIG>, the posterior tools are used to deliver lenses in <NUM>. 25D increments (e.g., <NUM>. 00D, -<NUM>. 75D, -<NUM>. 50D, <NUM>. 25D) and are shown along the top x-axis of the matrix. The anterior tools can be spaced to deliver <NUM> diopter increments (e.g., -3D, -4D, -5D, etc.) and are located along the left y-axis of the matrix. The resultant lens powers are indicated at the intersection of a given posterior tool and a given anterior tool.

In order to provide greater manufacturing flexibility the difference between the posterior tools can be again further subdivided into step (or incremental) tools to provide a level of discrete control over the power of the lens that can be produced from resultant posterior and anterior molds from the tooling within the table or matrix. Reference is now made to <FIG>, which illustrates a table with three additional posterior step tools on the top x-axis to the left and right of the -<NUM> D tool. As shown in <FIG>, there are three posterior step tools with a diopter less than -<NUM> D and three posterior step tools with a diopter greater than the -<NUM> D tool. These additional posterior step tools allow the system to produce resultant lenses that have powers in increments of <NUM> D by selecting alternate posterior tools. Accordingly, as can be seen by a comparison between the table in <FIG>, as a given matrix allows for finer adjustments between the resultant lens power, the complexity of the matrix increases. This in turn increases the number of posterior tooling required to make each lens.

One exemplary method utilized to effectively space out the step tooling increments to accommodate many different lens power requirements involves determining the distance in millimeters (mm) between the posterior radii equivalent to a <NUM>. 25D differential in power. This is shown in <FIG>. The subsequent step tools radii values are then determined by subdividing this figure into the required number of steps. However, one of the effects of this method is that the spherical aberration (SA) for each lens at a given power changes significantly across the steps and the process becomes unable to maintain a consistent SA. For instance, as shown in <FIG>, if the anterior tool radius remains constant and the posterior tool radius is changed incrementally between <NUM> and <NUM>, the resultant spherical aberration will fluctuate between -<NUM> and -<NUM>.

Embodiments of the present disclosure reduce fluctuations in the spherical aberration between different posterior tools by varying the amount of conic on posterior tools. Embodiments also include varying the amount of conic on the posterior mold lens-molding surface while maintaining a constant amount of conic on the anterior lens-molding surface such that spherical aberration on a lens formed by the posterior and anterior molds is within a predetermined range. Embodiments further provide that the predetermined range is a variation in spherical aberration of less than <NUM>%, preferably less than <NUM>%, and most preferably less than <NUM>%. Embodiments of the present disclosure provide that only specific steps can be used to create a given power in order to keep the SA value within a predetermined range. For instance, by varying the amount of conic on the posterior tools, two or more posterior tools with a different posterior tool radius could produce a lens with the same power, but with different SA values.

Exemplary embodiments of the present disclosure provide for incremental step tooling of the posterior tool structured around specific steps to limit the range of SA produced in the resultant lenses. Embodiments provide that the incremental steps cannot be used to produce lens powers outside of a given range in order to keep the SA close to a predetermined value. As a result, for the case that a given step is <NUM>. 25D, each <NUM>. 25D step will have its own corresponding set of step tools unique to that group. This can have the net effect of increasing the number of posterior tools required to produce a given set of lenses having powers within a certain range. This can become a significant number of tools, which are difficult to manage.

Embodiments of the present disclosure provide a matrix array with anterior tools spaced in 1D increments, posterior tools in <NUM>. 25D increments, and posterior step tools in <NUM>. 0625D increments to achieve a desired lens power. Embodiments of the present disclosure also provide a method to maintain consistent spherical aberration (SA) levels in the resultant lens by optimizing or adjusting the conic constant of the posterior step tool or the anterior step tool. An exemplary benefit of aspects of the present disclosure is that any posterior step tool can be used with any given anterior tool and the resultant value of SA will be within predetermined limits or bounds.

One embodiment provides for setting or identifying the resolution of lens tooling by selecting a main step change of diopter power. This embodiment includes selecting a number of incremental steps to be determined within the main step change, calculating an incremental change of power for at least one incremental step, and varying a conic constant for the calculated incremental change in power to maintain the spherical aberration of the resultant lens within a predetermined range. According to the invention, provided is a tooling set for forming mold halves for forming an ophthalmic device from a curable monomer mixture. The tooling set includes an anterior tool set having a plurality of anterior step tools, each anterior step tool having an optic defining surface, and the anterior tools configured to provide resultant diopter step increments. The step tool further includes a posterior tooling set having a plurality of posterior step tools and a plurality of incremental tools, each incremental tool having a unique conic constant, and wherein each incremental posterior step tool can be used with each anterior step tool to provide a resultant spherical aberration within a predetermined range.

Embodiments of the present disclosure further remove the necessity to band or group posterior tools, or to produce multiple posterior tools of effectively the same radii but with different levels of conic. Accordingly, an overlapping system with multiple similarly designed posterior tools can be replaced with a system that requires over <NUM>% less posterior tools in the overall tooling matrix. This in turn can provide a significant cost and efficiency savings in manufacturing.

In one embodiment, the main <NUM>. 25D steps can be subdivided into incremental units of diopters to obtain the desired lens characteristics rather than in mm of radius of the posterior mold. Embodiments provide that the change in power for each posterior mold includes subdividing each <NUM>. 25D step into four <NUM>. 0625D steps. Although four steps are discussed, it is understood the incremental steps could include <NUM>, <NUM>, or more. For example, if the -<NUM>. 00D posterior step tool is derived using an anterior radius of <NUM>, a thickness of <NUM>, and a conic of -<NUM> in combination with a posterior radius <NUM> and <NUM> conic, the resultant lens will have a power of -<NUM> and SA of -<NUM>. The next step tool in the series can then be determined by adding <NUM>. 0625D (the desired power incrementation) to -<NUM>. 08D to give -<NUM>. This value of -<NUM>. 017D then becomes the next target power with a subsequent re-optimization for SA. This process is then repeated for each required step tool. The results and proof of the effectiveness of this methodology are detailed in <FIG> and <FIG>. Embodiments provide that the spherical aberration produced using this method in the resultant lenses is within a range of <NUM> to <NUM>.

In <FIG>, shown is a graph illustrating the change in power with an exemplary step tool in accordance with exemplary embodiments of the present disclosure. As shown in <FIG>, the y-axis indicates the change in power (D) with markings in increments of <NUM>. The top x-axis indicates the steps of the nominal cylinder power (D) for the posterior mold. In <FIG>, the -<NUM>. 00D posterior step tool is used as an exemplary starting point at <NUM>. 00D on the x-axis for all cylinders. For each subsequent posterior tool the change in power away from -<NUM>. 00D is shown. Plotted on the graph in <FIG> is an anterior mold with -1D, -3D, -6D, -9D, +2D, and +4D. As is evident, the data points are constant relative to the y-axis, indicating that a change of either +<NUM> or -<NUM> is consistently being delivered. The plot line remains constant for all anterior powers.

Reference is now made to <FIG>, which depicts a graph with spherical aberration values that correspond to the step tools used in <FIG>. Shown in <FIG> along the y-axis is the change in spherical aberration in µm for the resultant lens. Along the x-axis is the nominal cylinder power of the posterior step tool. Plotted on the graph is the spherical aberration of a given resultant lens for an anterior mold having -1D, -3D, -6D, -9D, +2D and+4D. As is evident by the plot of the lines in <FIG>, each step in the posterior tool along the x-axis for each anterior power has an absolute value of spherical aberration that is maintained within a saw tooth shaped band approximately between -<NUM> and -<NUM>. It should be appreciated that embodiments of the present disclosure provide that a spherical aberration target amount can be maintained within a saw tooth shaped band having a range of approximately <NUM> of the target amount.

Embodiments of the present disclosure provide that every posterior step tool has its own unique value for conic constant. The benefit of this approach is realized in the fact that any posterior step can be used with a given anterior tool and the resultant value of SA will be within a predetermined range. Embodiments remove the necessity to band or group posterior tools or to produce multiple posterior tools of effectively the same radii, but with different levels of conic.

Referring to <FIG>, presented is an exemplary logic flow diagram in accordance with a method and apparatus for performing exemplary embodiments of this disclosure. Block <NUM> presents (a) providing a plurality of posterior tools each having a posterior optic defining surface and a plurality of anterior tools each having an anterior optic defining surface, wherein each one of the plurality of posterior tools has a different central posterior optic defining surface including a unique conic section; (b) selecting one of the plurality of posterior tools and one of the plurality of anterior tools based on a criteria; and (c) forming a posterior mold by the selected one of the plurality of posterior tools and an anterior mold by the selected one of the plurality of anterior tools, the posterior mold and the anterior mold operable to form an ophthalmic lens having the criteria. Then block <NUM> specifies wherein each one of the plurality of posterior tools, when paired with each one of the plurality of anterior tools, provides a lens with a unique spherical power correction.

Claim 1:
A method of forming contact lenses, the method comprising:
(a) providing a tooling set for forming mold halves for forming an ophthalmic device from a curable monomer mixture, the tooling set comprising a plurality of posterior step tools and a plurality of incremental tools, each incremental tool having a unique conic constant, and each having a posterior optic defining surface and a plurality of anterior step tools each having an anterior optic defining surface, and the anterior tools configured to provide resultant diopter step increments wherein each one of the plurality of posterior tools has a different central posterior optic defining surface, and wherein incremental posterior step tools can be used with each one of the plurality of anterior step tools to provide a resultant spherical aberration within a predetermined range;
(b) selecting one of the plurality of posterior step tools and one of the plurality of anterior tools based on a criteria, wherein the criteria includes a spherical power correction; and
(c) forming a posterior mold (<NUM>) by the selected one of the plurality of posterior step tools and an anterior mold (<NUM>) by the selected one of the plurality of anterior step tools, the posterior mold (<NUM>) and the anterior mold (<NUM>) operable to form a contact lens having the criteria, wherein each one of the plurality of posterior step tools, when paired with each one of the plurality of anterior step tools, provides a lens with a unique spherical power correction, wherein each said lens with a unique spherical power correction has a spherical aberration value within a predetermined range, and wherein said spherical aberration value is within a range of about <NUM> to about <NUM>.