HK1088667B - Contact lens - Google Patents

Description

Contact lens

RELATED APPLICATIONS

The present application claims priority from U.S. provisional patent application No.60/193493 entitled to 2000 on 31/3, from 35u.s.c. § 119 (e).

Background

The present invention relates to contact lenses, and more particularly to an improved ballast, preferably prismatic, for toric lenses for producing low torque rotational correction of the lens.

Astigmatism is a defect of the eye to be corrected with a lens having an aspherical structure. The above-described structure, often represented as a cylinder on a patient's prescription, will impart to at least a portion of the lens surface the shape of a toric portion. A toric surface is a surface or solid formed by a circle rotated about an axis other than its own axis. For example, the toroid has the shape of a toric surface and the toric portion of the lens is a small elliptical portion on the toric surface having a major axis and a minor axis. Due to this non-axisymmetric configuration, the proper rotational orientation of the lens must be maintained. It must be noted that other lenses, such as those that provide bi-focal or multi-focal corrections, are also non-axisymmetric and therefore have a particular orientation beyond which performance is poor.

Astigmatism is often associated with other refractive errors, such as myopia or hyperopia, so toric contact lenses often also provide some negative or positive spherical correction. Although the concave or posterior surface of a contact lens is generally spherical in shape, where astigmatism is corrected with a lens, the posterior surface of a contact lens typically has a toric shape, that is, the curved portion of the posterior surface of the lens has a major axis and a minor axis. The radius of curvature of the rear face of the lens in the direction of the major axis is greater than the radius of curvature in the direction of the minor axis. The major diameter of the toric surface is typically less than the diameter of the entire lens; and cut into an initial spherical base curve. Additionally, the anterior and/or posterior surfaces of the lens region may have a spherical portion that facilitates distance refractive correction, typically provided by the outer or anterior surface of the lens. Of course, some configurations have a toric surface on the anterior face, and spherical correction may be provided on either the anterior or posterior face.

Although the ophthalmic lens can be rigidly positioned and secured by the frame, the toric contact lens must be stably positioned to substantially stabilize the cylindrical correction in the corrected position of the eye. In the prior art, soft contact lenses, which are well known, have been used to correct astigmatism. Generally, these contact lenses rely on several types of stabilization mechanisms or stabilization methods to properly position the lens within the eye. The stabilization zone for contact lenses is typically formed by incorporating a member in front of the lens or behind the lens or between the front and back. Such a positioning member is intended to take advantage of the force of the blinking eye on the resulting eyelid. When the eyelids touch the contact lens, they can press the lens downward against the cornea and move the elevational surface features.

A so-called "wedge" or "prism" stabilization zone may be used in which the lower portion of the lens is thicker than the upper portion, so that the upper eyelid moves more than the lower eyelid, and the upper eyelid applies more force to the contact lens to more easily move the lower portion of the contact lens downward, thereby automatically rotating the contact lens along the cornea into the desired orientation. Additionally, contact lenses may also employ a stabilization method called a "peripheral stabilization zone" ("peripheral stabilization zone" shorthand) that includes a stabilization zone that surrounds but does not include the central lens zone.

Examples of such prismatic stabilizing regions are disclosed in U.S. Pat. Nos. 4573774, 5125728 and 5020898 and PCT publication No. WO98/45749. Other contact lens positioning structures include methods of making the upper and lower regions thinner than the thicker central region, such as shown in U.S. patent nos. 4095878 and 5650837. additionally, channels or ridges may be provided in the contact lens, as described, for example, in PCT publication No. au92/00290.

U.S. patent No.5020898 discloses a toric contact lens having a stabilization zone disposed outside the anterior lens zone, the stabilization zone having a thickness that gradually thickens from the upper portion of the contact lens to two points of maximum thickness near the lower portion periphery.

U.S. patent 5125728 also discloses a stabilization zone portion that thickens from the upper portion of the contact lens to its two lower peripheral edges to a maximum thickness that is positioned as close as possible to the lens edge so that these stabilization zone portions match the surrounding cornea and conjunctiva to limit lens rotation. A non-stabilized zone of minimal resistance is provided above and below the central lens region in the vertical central portion of the contact lens. The above patent alleges that the narrow zone without a stabilization zone in combination with the thicker stabilization zone and the thicker portion near the lens periphery may form an improved stabilization mechanism.

Finally, PCT publication No. wo98/45749 describes a stabilized lens having a prism body passing through the lens zone. The diameters of the anterior and posterior lens zones of the lens are selected to control the thickness of the upper and lower portions of the anterior adjacent lens zones when combined into a lens.

In addition to the relative ability of the lens to be constantly positioned on the cornea, other factors can affect the performance of various stabilizing structures. For example, some structures are better than others in one or more of the following ways: reducing the overall thickness of the toric contact lens to provide a physiological benefit to the wearer; the manufacture is easy; reducing the lens parameter items; clinical performance includes the consistency of fit between the wearer's comfort and refractive power. With respect to the comfort aspect of the wearer, generally, the thinner and smoother the surface of the lens, the more comfortable the wearer will feel. Additionally, it is known that making the lens periphery thinner and shaped can also increase comfort.

The main problem of the existing toric contact lens structure is large variation of orientation. And/or the difference in comfort level felt by the various wearers is large for a given structure. In addition to the lens structure and material, patient factors also affect the positioning of the toric contact lens in the eye and increase the variation in lens orientation. The above-mentioned patient factors, such as the characteristics of blinking and visual parameters such as the shape and configuration of the eyelids, cornea, and conjunctiva, may produce undesirable interactions (e.g., asymmetry); or insufficient interaction force with the contact lens. However, many of the problems associated with prior art mechanisms can be attributed to the failure of the stabilization mechanism to maximize eyelid interaction to reduce variations in lens orientation between wearers.

Despite the many efforts in this area, there remains a need for toric contact lenses having stabilization characteristics that are more consistent among wearers.

Summary of the invention

In accordance with the present invention, a contact lens having improved thickness and stabilization zone structure is provided. The contact lenses of the present invention can reduce the well known variation in lens positioning between wearers. Moreover, the contact lens of the present invention provides for more effective interaction between the stabilization mechanism and the eyelid during blinking, and desirably has a peripheral zone that is desirable for wearer comfort.

Accordingly, in one aspect, the present invention provides a contact lens having a contact lens body with a substantially spherical, substantially curved surface (including an anterior convex surface and a posterior concave surface) and an outer periphery located between the anterior convex surface and the posterior concave surface, the outer periphery adjacent the anterior convex surface forming a peripheral zone. The lens body has a thickness between the anterior convex surface and the posterior concave surface, and is non-axisymmetric to form an upper periphery and a lower periphery, and a vertical meridian is formed from the upper periphery toward the lower periphery and a horizontal meridian is formed perpendicular to the vertical meridian. The anterior convex surface has a plurality of zones therein including an inner zone surrounded by a peripheral zone and a lens zone located substantially in the center of the inner zone. In addition, the contact lens has a prismatic ballast portion such that the thickness of the lens in at least the ballast portion of the inner zone increases along a vertical meridian from the upper periphery to the lower periphery. The inner region has an upper portion between the lens region and an upper limit of the inner region, a lower portion between the lens region and a lower limit of the inner region, and a middle portion between the upper and lower portions. Forming the ballast portion in one or more of the upper, intermediate and lower portions, the ballast portion having a series of continuous horizontal cross-sections, excluding the peripheral zone and the lens zone, and spanning a distance of at least 20% of a minimum dimension of the upper, intermediate and lower portions measured along a vertical meridian, wherein each horizontal cross-section has a substantially uniform thickness that does not vary by more than 30 μm or about 20% of a greater absolute value. In one embodiment, the thickness within each successive horizontal section of the contact lens does not vary by more than about 15 μm or 10%, whichever is larger in absolute value.

In one embodiment, the stabilizer section is formed entirely within only one of the upper, middle and lower portions. In another embodiment, the stabilizer section is formed entirely within only two of the upper, middle and lower sections. In yet another embodiment, the stabilizer section is formed in all 3 sections of the upper section, the middle section and the lower section.

In a preferred embodiment, the rate of change of thickness in the peripheral zone of the band slope is less than about 250 μm/mm, more suitably less than about 200 μm/mm.

In an alternative embodiment, the contact lens of the present invention has a contact lens body having a substantially spherical base curve including an anterior convex surface and a posterior concave surface and an outer periphery located between the anterior convex surface and the posterior concave surface. A peripheral zone is formed adjacent the outer periphery of the lens and has a thickness that decreases toward the outer periphery of the lens. The mirror body has a thickness between the anterior convex surface and the posterior concave surface, and is non-axisymmetric, thereby forming an upper perimeter and a lower perimeter. A vertical meridian is formed from the upper periphery to the lower periphery, and a horizontal meridian perpendicular thereto is formed. The anterior convex surface has a plurality of zones therein including an inner zone surrounded by a peripheral zone and having a prismatic ballast portion and a lens zone located substantially centrally of the inner zone, wherein the thickness of the lens in at least the prismatic ballast portion of the inner zone increases in a vertical meridional direction from the upper periphery to the lower periphery. The distance between the inner region and the outer periphery along a 225 DEG meridian is less than about 1.4 mm.

In accordance with one aspect of the invention, a molded contact lens has a fully molded (i.e., molded on both the anterior and posterior sides) contact lens body having the general characteristics described above. As previously mentioned, the molded contact lens has a prism ballast portion in an inner zone, the distance along the 225 ° meridian between the inner zone and the outer periphery being less than about 1.8 mm. On the other hand, it is also desirable that the distance along the 270 ° meridian between the inner zone and the outer periphery is less than about 2.1mm, and the distance along the 180 ° meridian is less than about 1.3 mm.

Desirably, the area surrounded by and surrounding the peripheral zone is generally annular, that is, an upper distance A is formed along a vertical meridian from the lens zone to the peripheral zone in the inner zone, and a lower distance B is formed along a vertical meridian from the lens zone to the peripheral zone in the inner zone. For molded prismatic stabilized contact lenses, the annular zone is in the range: b is more than or equal to 0.33A and less than or equal to A, and the annular area of the contact lens with the prism stabilization zone is in the following range: b is more than or equal to 0.55 and less than or equal to A.

Each feature described above, and any combination of one or more of the above features, is included within the scope of the present invention provided that the features included in the combination are not mutually inconsistent.

The invention, together with further features and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying exemplary drawings, in which like reference numerals identify like parts.

Brief description of the drawings

FIG. 1 is a simplified front view of a contact lens of the present invention showing various areas defined within the contact lens;

fig. 2 shows a series of (a-a 'to E-E') horizontal cross-sections through the contact lens of fig. 1.

FIG. 3 shows a thickness variation curve along the vertical meridian for the contact lens of FIG. 1;

FIG. 4a is an exemplary topographical pattern of contact lenses of the present invention with thickness numbers;

figure 4b is a graph showing the discontinuity and angular relationship that exists between the partial areas of the contact lenses of the invention.

FIGS. 5 a-5 d are front views of various contact lenses of the invention having spherical front lens zones and zones of substantially uniform horizontal thickness, respectively;

FIGS. 6 a-6 d are front views of various contact lenses of the invention having a toric front lens zone and zones of substantially uniform horizontal thickness, respectively;

FIG. 7 is a simple front view of a contact lens with numbers marked on the meridian used as a reference; and

fig. 8 is a simple front view of a prior art contact lens showing various areas defined within the contact lens.

Description of The Preferred Embodiment

The present invention provides a stabilized contact lens, particularly a contact lens having cylindrical correction for astigmatism. More broadly, the present invention provides contact lenses having an elevational surface that interacts with the blinking motion of the eyelids to stabilize the lens during rotation. Rotational stability is useful for any non-axisymmetric contact lens, for example, a toric lens or multi-focal lens must maintain its rotational orientation for proper correction. However, it must be understood that rotational stability is also desirable for other specially made lenses.

In the following description, the various surfaces and thicknesses of the contact lens of the invention will be described with reference to a simple front perspective view in which the lens has been flattened. Contact lenses typically have a substantially spherical curvature with a convex front surface and a concave rear surface. The various surfaces and lens regions of which are molded or machined from the base sphere. The front view is shown flattened for simplicity and with the base sphere removed, thus eliminating the shadow lines corresponding to the basic spherical curvature, and thus more clearly showing the particular surfaces and thicknesses of the present invention. In a preferred embodiment, the contact lens of the present invention has a negative spherical power distance correction and a toric surface for cylindrical correction.

FIG. 1 shows a simplified front view of a curved contact lens 20 of the present invention, flattened without hatching to indicate the areas therein. The contact lens 20 has a lens body made of a suitable soft material or rigid material. Soft contact lenses are typically made from hydrophilic materials such as hydroxyethyl methacrylate, organometallic substances, silicone rubber, silicone hydrogel, urethane, and the like. Alternatively, rigid, breathable materials such as silicone acrylates or fluorosilicone acrylates may be used. The lens body has a generally spherical curved surface with a concave posterior surface for contacting the cornea opposite an outwardly facing convex anterior surface.

Referring to fig. 1, a contact lens 20 has a lens region 22, a peripheral region 24, and an interior region 26 defined by the peripheral region, wherein the lens region 22 forms a portion of the interior region 26. Alternatively, the inner zone 26 may be formed between the lens area and the peripheral zone. As will be explained below, the lens region 22 may be circular, toric or other specific shape. The radial dimension (width) of the peripheral zone 24 may be uniform or may vary. In the exemplary embodiment shown, the radial dimension at the upper end 30 of the peripheral zone 24 is smaller and the radial dimension at the lower end 32 is wider. In other words, the inner region 26 has a circular periphery or ballast periphery 34 that is slightly offset from the top of the contact lens 20 along a vertical meridian or centerline Z-Z' therethrough. It should be noted that the clear outlines between lens region 22, peripheral region 24, and inner region 26 in the figures do not imply discontinuities or bevels at these locations, and in fact, the gradual curved transitions between the regions of the exemplary contact lens of the present invention.

The edge 36 of the lens is the intersection of the anterior convex surface and the posterior concave surface. Peripheral zone 24 is preferably tapered so that the lens edge 36 is thinner than the circular stabilization zone perimeter 34, in which regard peripheral zone 24 preferably has a partially tapered surface (although the tapered surface is superimposed on the underlying spherical surface). Additionally, peripheral region 24 may have a local spherical or other curvature (i.e., shape) such as any suitable curved surface.

It is believed that the various features of the contact lenses 20 of the present invention make them more comfortable to wear than other similar contact lenses. In fact, certain clinical trials have concluded that: the patient responds more satisfactorily to the comfort level of the contact lens of the invention than a similar contact lens.

The inner zone 26 may be divided into 3 sections along the vertical meridian Z-Z'. Specifically, the upper portion 40 is located between the upper portion of the stabilization zone perimeter 34 and the upper portion of the lens zone 22, divided into upper, middle and lower 3 sections. As depicted by imaginary line 42 perpendicular to meridian Z-Z', intermediate portion 44 lies between an orthogonal line 42 of the meridian and a second orthogonal line 46 of the lower portion of lens zone 22, and finally, lower portion 48 lies between second orthogonal line 46 and the lower portion of stabilization zone periphery 34, so that lens zone 22 lies entirely within intermediate portion 44.

In the present application, the inner region 26 is divided into separate regions by the upper portion 40, the middle portion 44, and the lower portion 48, which form a particular stabilizing surface. In this regard, however, it should be understood that the split lines 42, 46 between the regions may be varied and may be non-linear. In one aspect, the present invention relates to a specific plateau surface or prismatic plateau surface/thickness of one or more portions of the inner zone 26 that may be defined by a variety of methods. Accordingly, the reader will appreciate that the above-described portions 40, 44, and 48 are by way of example only. Desirably, at least 20% (as measured in percent of the vertical dimension), preferably at least 50%, and more preferably at least 100% of at least one of the portions 40, 44, and 48 forms a constant thickness plateau surface. More specifically, a prism stabilizing section of uniform thickness is formed within one or more of the upper, intermediate and lower sections 40, 44, 48, which has a series of continuous horizontal cross-sections, except for the peripheral and mirror regions, and spans a distance of at least 20% of the smallest dimension of the upper, intermediate and lower sections, as measured along the vertical meridian. The term "equal thickness" as used above means that the respective thicknesses of the continuous horizontal cross sections are substantially uniform and vary by no more than about 30 μm or 20%, whichever is greater in absolute terms. In a particularly preferred construction, the plateau surfaces are formed in at least two, and more preferably all 3, of the upper, middle and lower sections 40, 44 and 48.

The present invention relates to contact lenses having a rotational stabilization mechanism, and so-called "dynamic stabilization" contact lenses, the stabilization mechanism described above including a lens having a stabilization zone, such as a prism cylinder stabilization zone; a peripheral stabilization zone. Contact lenses with stabilization zones have some raised surface profile that an eyelid can encounter to reposition the contact lens generally about its optical axis. The prism ballast has a wedge-shaped or sloped ballast for interacting with the eyelid even in the lens zone, while the peripheral ballast is located outside the lens zone. Dynamically stabilized contact lenses contain upper and lower flats on the lens that form a thickened central section for interaction with the eye, see U.S. patent No. 4095878. Those skilled in the art will also recognize that there are other such stabilizing mechanisms that may be advantageously employed with the present invention.

FIG. 1 also shows a plurality of typical section lines A-A ', B-B', C-C ', D-D' and E-E 'perpendicular to the vertical meridian Z-Z' (i.e., along the horizontal), which are shown in FIG. 2, with the basic spherical curvature of each section being shown in FIG. 2. The present invention provides contact lenses having continuous horizontal cross sections with a stabilization zone as shown in fig. 2, each cross section having a thickness that is substantially uniform or substantially equal except for lens region 22 and peripheral region 24. For example, one cross-section having a ballast region, such as D-D' in FIG. 2, is of substantially uniform thickness, and all cross-sections having a ballast region shown in FIG. 2, except for the lens region 22 and the peripheral region 24, are of substantially uniform thickness.

It is desirable that each cross section having a substantially uniform thickness has a thickness variation within the cross section of not more than about 30 μm or about 20%, on the absolute basis. In one embodiment, the thickness variation within each cross-section is no greater than about 15 μm or about 10%, such as no greater than about 10 μm or about 7%, whichever is large in absolute terms. The thickness variations described above will be understood to be small enough to still consider each section to have a "substantially uniform" thickness.

In an exemplary embodiment of the invention, the contact lens 20 has a so-called prism stabilization zone superimposed on the lens throughout the inner zone 26. That is, the thickness gradually increases from the intersection of the stabilized zone perimeter 34 with the vertical meridian Z-Z' at the upper portion of the contact lens 20 to the intersection of the same two lines at the lower portion of the contact lens. Figure 3 shows the distribution of the above thicknesses along the vertical meridian in a graph, with the upper portion 30 of the peripheral zone 24 on the right and the lower portion 32 of the peripheral zone 24 on the left. Looking first to the right, the slope can be seen in the upper portion 30 of the peripheral region 24 from the edge 36 to the upper portion of the stabilization zone perimeter 34. Within the upper portion 40, the thickness gradually increases to a horizontal section line 42. The thickness is further increased by the lens region 22 to the horizontal line 46. Having the greatest thickness from lower portion 48 to the lower portion of stabilization zone perimeter 34. The lens again has a downward slope in peripheral zone 24 from stabilization zone periphery 34 to lower edge 36.

Thus, the thickness profile shown in fig. 3 corresponds to a prism stabilization zone within the contact lens 20 through all portions of the upper portion 40, the intermediate portion 44, and the lower portion 48. In fact, even in the lens region 22, there is a prism stabilization zone as described above. Importantly, the present invention forms prismatic stabilization zones within at least one of the portions 40, 44 and 48 of uniform horizontal cross-sectional thickness. Thus, as shown in FIG. 2, all of the illustrated cross-sections have a uniform thickness along their width except for the peripheral region 24, although the thickness of each cross-section increases from section A-A ' to section E-E ' as the thickness increases from top to bottom in a direction parallel to the vertical meridian Z-Z '.

The uniform thickness of the horizontal cross section helps stabilize the contact lenses of the invention, unlike previous contact lenses. More specifically, the contact lens of the present invention is more adaptable to a larger number of wearers than prior art contact lenses because it employs a uniform thickness or a uniform thickness configuration that results in less torque on the lens by the eyelids. The constant thickness plateau configuration described above maximizes eyelid interaction with the contact lens by allowing the eyelids to move the lens up and down during blinking to achieve uniform contact along each cross-section of the lens. In contrast, prior art contact lenses, during normal blinking, produce a large torque when the eyelids interact with a horizontal cross section of the lens of non-uniform thickness. This is because the contact lens is properly positioned on the eye, so there should be maximum lens-eyelid interaction along the lens (i.e., along each horizontal section) to press the lens into the desired orientation < overall orientation > with minimal fluctuation when blinking < inter-blink orientation >.

Prior art contact lenses are more likely to develop non-uniform lens-eyelid interactions along the horizontal cross-section due to the narrow maximum thickness peaks or points on each side of the vertical meridian. In addition, the horizontal distance between the peaks of maximum thickness in prior art contact lenses generally increases from the superior portion to the horizontal midline and then decreases from the horizontal midline to the inferior portion, which in turn further varies the lens-eyelid interaction force.

The uniform horizontal cross-sectional thickness contact lens 20 of the present invention has proven to perform better than other similar contact lenses in terms of maintaining the contact lens in the correct rotational orientation in the eye. Clinical trials have shown that the position of the positioning marks on the lens varies little throughout. For example, a group of 20 persons was simultaneously studied to determine the location of the alignment marks on each lens in the eye all the way through and the standard deviation of the location of the alignment marks, and the results showed that the measured standard deviation of the contact lens of the present invention was smaller than that of the other contact lenses, which means that the contact lens of the present invention had higher rotational stability in the eye.

The topographical mapping of fig. 4a identifies typical values for the thickness of the contact lens 20 having the thickness profile shown in fig. 3. It will be appreciated that the contact lens shown in figure 4a is generally circular. In fig. 4a, the inner zone 26 is divided into a plurality of individual cells by horizontal and vertical network lines. Each horizontal row of cells has a uniform thickness throughout the inner region 26. On the other hand, the thickness of the cells along a vertical column increases from top to bottom. For example, horizontal rows 50 have a uniform thickness of 150 μm except in the lens area, run vertically to 52, have an upper portion of 70 μm thickness, increase downward to 280 μm, and begin to decrease in thickness in the lower portion just prior to entering the peripheral region 24. The thickness values shown in fig. 4a are exemplary and are suitable for soft hydrogel contact lenses. The values described above for contact lenses made of other materials may vary depending on the optical or other properties of the particular material.

The reader will appreciate that the values of the individual cells plotted in FIG. 4a represent the average thickness value within each cell. That is, the thickness of the contact lens 20 is gradually varied without a stepped boundary between cells. More generally, although the present application describes various regions or portions within a sticker, these regions are shown merely to clearly illustrate the invention. Those skilled in the art will appreciate that these different areas of the contact lens do not differ significantly from one another, but rather blend smoothly with one another.

Fig. 4a also shows a reduction in thickness or change in slope of contact lens 20 in peripheral zone 24. For example, at the lower midpoint, the decrease in thickness is, in turn, 210-140 μm, which can also be seen on the graph of FIG. 3. The above-described slope in the peripheral zone 24 creates a so-called comfort zone along the edge of the contact lens. Due to the reduced thickness, the eyelid is facilitated to move along the contact lens. In particular, the eyelid is more likely to weigh down the peripheral zone 24 with a slope than a contact lens with a larger abrupt change in peripheral thickness.

In one exemplary embodiment, the contact lens 20 has a corneal fitting relationship that maintains the lens centered on the cornea, preferably a contact lens diameter sufficient to cover the entire cornea, with optimal stability so that the lens does not loosen, and is stable at both gaze and blinking, which is beneficial to the wearer's vision and comfort. For optimum lens-cornea fit, the sagittal depth (concave depth of the back curve) is about 3.0-5.0 mm within a range of about 13.0-16.0 mm for a contact lens diameter. More preferably, the diameter of the contact lens is 13.5 to 13.8 mm. The thickness of the contact lens edge 36 is preferably less than about 120 μm, more preferably about 90 μm. In this regard, the thickness is measured radially with respect to the front curve. The outermost edges of the edges 36 may include a suitable rounding of the corners of the lower edges.

Multiple meridians may be made by fitting the center of the lens. In a preferred embodiment, the rate of change of the radial thickness of the lens along any meridian of the lens from the end of the stabilized zone 34 to the edge 36 (i.e., the peripheral zone 24) is less than about 250 μm/mm for maximum comfort to the wearer. For example, in the topographical pattern of FIG. 4a, the rate of change in thickness along any meridian in the peripheral region 24 is less than about 250 μm/mm. More preferably, the rate of change in thickness in the peripheral region 24 is less than about 200 μm/mm.

The advantageous interaction between peripheral zone 24 and zones of equal thickness is further exemplified below by measurements taken along the lens near the edge 36 of the lens closest to the point of thickness. To illustrate this principle, figure 7 shows various meridians in degrees that move counterclockwise around the lens through the optical axis and starting from the 3 o' clock position. Of course, since the thicknesses within the inner zone 26 are equal, the point of maximum thickness along any meridian corresponds to the thickness along the entire horizontal meridian except for the lens zone. Thus, the beginning of the inner region 26 and the point of maximum thickness along any meridian is always located on the plateau perimeter 34. However, with the provision of a suitable stabilizing zone, the maximum thickness value along the stabilizing zone perimeter 34 varies.

For the inventive contact lens with a prismatic ballast, the distance between the point of maximum thickness (i.e., the ballast periphery 34) and the lens edge 36 is no greater than about 1.4mm along the 225 meridian regardless of thickness. In accordance with the present invention, the maximum thickness along the 225 ° meridian of any type of contact lens having a stabilized zone is about 200 to about 400 μm, preferably about 250 to about 350 μm, and more preferably about 320 μm. Along the 270 meridian, and regardless of thickness, although thicknesses on the order of 320 μm are suitable, the distance between the point of maximum thickness (e.g., the periphery 34 of the ballast region) and the edge 36 of the lens is no greater than 1.8 mm. For a fully molded prismatic ballast (i.e., molded lenses both anterior and posterior), the distance between the point of maximum thickness along the 225 meridian (e.g., the periphery 34 of the ballast) and the peripheral edge 36 is less than about 1.8mm, and preferably, the distance between the point of maximum thickness and the peripheral edge 36 along the 270 meridian is less than about 2.1 mm. In addition, along the 180 DEG meridian, the distance between the inner zone and the peripheral edge is less than about 1.3 mm. Generally, the peripheral zone 24 of the contact lens of the present invention is narrower than prior art contact lenses with a stabilization zone, as also described above, due to the appropriate thickness and thus the lower comfortable bevel angle in the peripheral zone 24.

Although the preferred contact lenses of the invention are smooth transitions between different portions thereof, the presence of separate borders or corners is not excluded. For example, the transition between peripheral region 24 and inner region 26 thereof may be formed by a rounded corner or a discontinuous transition on stabilization zone perimeter 34. Figure 3b shows an example of a transition between the plateau 26 and the peripheral zone 24 (i.e., at 34) along the Z-Z' meridian.

Fig. 5 a-5 d illustrate several variations of contact lenses of the invention that form different ballast portions within the ballast. For ease of illustration, the reader is referred back to the description of the definitions of the various portions (i.e., upper, middle, and lower portions) of the inner region 26 in FIG. 1. Figure 5a shows a contact lens 70 having a stabilization zone portion 72 disposed in an upper portion of the inner zone, and the inner zone is located between a lens zone 74 and a peripheral zone 76. Figure 5b shows a contact lens 80 of the present invention having a ballast portion 82 disposed in the upper and middle portions of the inner zone. Figure 5c shows a contact lens 90 having a stabilization zone portion 92 disposed throughout the inner zone, i.e., through its upper, middle and lower portions. Finally, fig. 5d shows a contact lens 100 having a ballast portion 102 disposed only in a lower portion of the inner zone.

Other modifications not shown include forming the stabilization zone portion entirely within the middle or lower portion of the inner zone or within both the middle and lower portions except for the upper portion. In addition, the ballast portion surrounds the lens region in a so-called "peripheral ballast" configuration, or continues through the lens region in a so-called "prism ballast" configuration.

Fig. 6 a-6 d illustrate various other contact lenses of the invention having a cylindrical correction zone in front of them. More specifically, a toric lens zone 110 is provided in each contact lens in the direction of its axis 112 that is rotated relative to the upper and lower axes of the lens. It is therefore apparent that a suitable stabilization zone needs to be provided for the lens to maintain a suitable offset orientation of the long axis 112.

Figure 6a shows a contact lens 120 having a ballast portion 122 that starts at the upper portion of the inner zone and then continues through the middle and lower portions. Fig. 6b shows a contact lens 130 having a stabilization zone portion 132 located entirely at a lower portion of the inner zone. Figure 6c shows a contact lens 140 having a stabilization zone portion 142 located entirely in the middle portion of the inner zone. Finally, fig. 6d shows a contact lens 150 having a ballast portion 152 located only in an upper portion of the inner zone.

FIG. 8 shows a prior art contact lens (Cooper Vi Soafrequency Xcel (Encore) Toric) having prism stabilization zones, where lines are drawn that mark the transitions between zones. Specifically, the stabilization zone 202 is separated from the lens zone 200 by a generally graphical inner line 204 and the stabilization zone 202 is separated from the peripheral zone 26 by a generally circular outer line 208, although the inner line 204 is preferably generally centered on the optical axis 0A, but the outer line 208 is offset upwardly along a vertical meridian 210. As a result, the stabilization zone 202 is wider in the upper portion than in the lower portion. In particular, the upper radial width a of the stabilizing zone 202 is significantly greater than the lower radial width B, and in fact, the upper radial width a may be more than twice the lower radial width B.

In contrast, as shown in FIG. 1, the inner zone 26 of the contact lens of the present invention is generally circular and has a radial width A that is less than about 300% of the radial width B. That is, for molded prismatic stabilization zones, the stabilization zones are annular and maintain the following relationship: b is more than or equal to 0.33 and less than or equal to A, and in addition, the annular area ranges of all the contact lenses with the prism stable areas keep the following relationship: b is more than or equal to 0.55 and less than or equal to A.

Obviously, the invention can be practiced with lenses having different powers, for example, the power of the contact lens of the invention can be about-8 to +8 diopters, although it is not necessarily limited to this range.

In addition, the contact lenses of the invention may have other stabilization features in addition to the uniform thickness stabilization zone structure described above. For example, the peripheral zone may have a flattened area for dynamic stabilization, or a peripheral stabilization zone stabilization feature may be provided outside the central lens area of the lens.

While the invention has been described above in terms of various specific examples and embodiments, it should be appreciated that the invention is not limited thereto, but may be practiced in a variety of ways within the scope of the following claims.

Claims (21)

1. A contact lens (20) comprising:

a viewing zone (22);

an inner zone (26) surrounded by the optic zone (22), the inner zone (26) including at least one region (40, 44, 48) of uniform horizontal thickness and a maximum thickness, said uniform horizontal thickness effective to rotationally stabilize the contact lens (20) on an individual's eye; the maximum thickness is in a region between an upper boundary and a lower boundary of the inner region (26).

2. The contact lens of claim 1, wherein the lens is a dynamically stabilized contact lens.

3. The contact lens of claim 1, wherein the inner zone includes a stabilization zone.

4. The contact lens of claim 3, wherein the stability zone is selected from the group consisting of a peripheral stability zone and a prismatic stability zone.

5. The contact lens of claim 1, wherein the lens is a toric lens or a multifocal lens.

6. The contact lens of claim 1, wherein the inner zone is asymmetric about a horizontal meridian of the contact lens (20).

7. The contact lens of claim 1, wherein the contact lens comprises a silicone grease hydrogel.

8. The contact lens of claim 7, further comprising a rounded edge at the intersection of the front and back surfaces of the contact lens.

9. The contact lens of claim 1, wherein the inner zone (26) comprises a plurality of zones (50) of equal thickness.

10. Contact lens according to claim 9, characterized in that the thickness zones (50) are oriented parallel to the horizontal meridian of the contact lens (20).

11. The contact lens of claim 1, the inner zone (26) including an upper zone (40), a lower zone (48) and a middle zone (44) between the upper zone (40) and the lower zone (48);

wherein the inner region (26) varies in thickness by at least 200 microns, and

the upper region (40) is of reduced thickness relative to the middle region (44) and comprises a plurality of horizontally oriented bands (50) of equal thickness extending from the upper edge of the inner region (26) towards the middle region (44), each band (50) having a thickness different from the thickness of each adjacent band (50), and the thickness of the upper region (40) increasing from the upper edge towards the middle region (44).

12. The contact lens of claim 11, wherein the superior region (40) is symmetric about a vertical meridian of the contact lens (20).

13. The contact lens of claim 11, further comprising a stabilization zone in a region selected from the group consisting of the superior region (40), the intermediate region (44), and the inferior region (48).

14. The contact lens of claim 11, wherein the thickness of the upper region increases non-linearly from the upper edge of the inner zone (26) to the intermediate region (44).

15. The contact lens of claim 11, wherein the thickness of the inner zone (26) increases non-linearly from its upper edge to the lower zone (48).

16. The contact lens of claim 1, further comprising:

a rear surface;

an opposing anterior surface including a vertical meridian (Z-Z'), a horizontal meridian, a central viewing zone (22) and a peripheral zone (30) surrounded by the inner zone (26);

wherein the inner zone (26) has a surface which, in combination with the posterior surface, forms a thickness profile in the inner zone (26) of the lens, the thickness profile is characterized by (1) a progressive increase in lens thickness from the top of the inner zone (26) down the vertical meridian or in a direction parallel to the vertical meridian until a maximum is reached at a location between the central viewing zone (22) and the lower edge of the inner zone (26), then reduced to the edge of the peripheral zone (30), or (2) symmetrical with respect to the vertical meridian (Z-Z'), has a substantially uniform thickness in a region (44) around the horizontal meridian and tapers in thickness from the region around the horizontal meridian up the vertical meridian (Z-Z') or parallel to the vertical meridian to the top of the inner zone (26).

17. The contact lens of claim 16, wherein the thickness profile is characterized by a lens thickness that gradually increases from the top of the inner zone (26) down the vertical meridian (Z-Z') or parallel to the vertical meridian until reaching a maximum at a location between the optic zone (22) and the lower edge of the inner zone (26) and then decreasing to the peripheral zone (30) of the lens (20).

18. The contact lens of claim 17, wherein the lens thickness distribution is symmetrical about the vertical meridian (Z-Z').

19. The contact lens of claim 17, wherein the anterior surface has a series of lines of constant thickness extending from one side of the lens to the other side of the lens, and wherein the thickness of the lens within the inner zone (26) remains substantially constant along each of the series of lines of constant thickness.

20. The contact lens of claim 19, wherein at least one of the thickness lines is a line parallel to the horizontal meridian.

21. The contact lens of claim 17, wherein the inner zone (26) includes a region of maximum thickness disposed below the central optic zone (22).