TWI390269B - Prescription lens and method of making same - Google Patents

Description

Prescription lens and method of manufacturing same

The present invention relates to a lens, and more particularly to a prescription lens and a method of manufacturing the same.

A lens used to correct the wearer's glasses such as myopia, hyperopia, astigmatism, and presbyopia, or sunglasses or a mask with incident light, wind, and foreign objects that are used to shield the wearer's high arc-bent field of view. The lenses used in the protective glasses of the type have specific optical properties consistent with the specifications of the prescription used by the wearer.

These lenses are typically specified to have a front curve lens surface that mates with the curved pattern of the eyeglass frame. As shown in the ninth figure, for a concave lens (900) having a front curve lens surface (910), the thickness of the lens edge (920) is thicker than other areas of the concave lens (900). The larger the front base curve of the concave lens, the thicker the lens edge of the concave lens. For example, in the case of a myopic prescription lens having a spherical mirror of -4.00, if the front base curve of the lens is 2.00, the back surface curvature of the lens should be 6.00. If the front base curve of the lens is 4.00, the back surface curvature of the lens should be 8.00. The edge thickness of the lens with a front base curve of 4.00 will be greater than the edge thickness of the lens with a front base curve of 2.00. Traditionally, patients with severe myopia prescriptions require very thick lenses. Therefore, traditionally myopic patients use a relatively flat eyeglass base curve to reduce excessively thick lens edges.

An edge-thickened lens can have many disadvantages such as blurring the wearer's field of view at a wide angle, unsightly, and increased lens weight.

In addition, since most of the sunglasses frame has a base arc of 6 or 8, and the conventional prescription lens uses a base arc of 2 to 4, the conventional prescription lens can hardly match the sunglasses frame. For example, in the case of a concave lens of -4.00, if the base curve of the eyeglass frame is about 6.00 (the front base curve of the lens should also be about 6.00), the curvature behind the lens should be cut to a base arc of 10, and Whether or not the lens has been resolved to match the chamfered surface of the eyeglass frame, the thickness of the lens will be very thick.

Therefore, there is a need for a technology that can address the aforementioned shortcomings and deficiencies.

One aspect of the invention relates to a method of making a prescription lens. In an embodiment of the invention, the method includes the steps of obtaining a lens prescription and data for mounting a prescription lens frame, wherein the prescription lens data includes a lens power, an optical area And the spherical front base curve, and the information of the eyeglass frame includes a frame curve.

The method further includes the steps of: calculating a maximum thickness of the lens of the prescription lens at the visual area according to the data of the prescription lens; selecting the lens according to the calculated data; and processing the lens to obtain a surrounding the visual area The transition zone and the prescription lens surrounding the edge portion of the transition zone cause the thickness of the edge portion to be substantially thinner than the maximum thickness of the lens at the visual region. In an embodiment, the frame curvature is characterized by the angle and inclination of the eyeglass frame. The ball front arc of the prescription lens cooperates with the frame curvature of the eyeglass frame.

The prescription lens has a geometric center and an optical center corresponding to the center of the vision area of the prescription lens. In an embodiment, the optical center substantially coincides with the geometric center. In another embodiment, the optical center is substantially offset from the geometric center.

In one embodiment, the prescription lens is a single vision lens. In another embodiment, the prescription lens is a multi-focal lens. Further, the prescription lens may be a plus lens or a near lens.

In one embodiment, the selected lens is a finished lens. The lens forming frame step is accomplished by projecting, casting, and turning the edge portion of the finished lens such that the thickness of the edge portion of the lens is substantially constant and thinner than the maximum thickness of the lens at the visual region.

In another embodiment, the selected lens is a semi-finished lens (hair blank). Forming a predetermined area of the semi-finished lens by a back arc, thereby forming a vision area, a transition area therein, and cutting an edge portion of the semi-finished lens to complete the lens forming frame step, so that the thickness of the edge portion is fixed and substantial The maximum thickness of the lens that is thinner than the visual area.

The prescription lens is formed by glass or plastic.

Another aspect of the invention relates to a prescription lens made in accordance with the above method.

Yet another aspect of the invention relates to a prescription lens. In one embodiment, the prescription lens has a ball front lens surface, a rear lens surface, and a lens body defined by the ball front lens surface and the rear lens surface. The lens body is characterized by a visual region, a transition region surrounding the visual region, and an edge portion surrounding the transition region, wherein the visual region is adapted to provide lens power according to a lens prescription used by the wearer. . The thickness of the edge portion is substantially fixed and thinner than the maximum thickness of the lens at the visual region. The lens body has a geometric center and an optical center corresponding to the center of the vision area. In an embodiment, the optical center substantially coincides with the geometric center. In another embodiment, the optical center is substantially offset from the geometric center.

The lens front surface of the ball is configured to mate with the frame curvature of the eyeglass frame. In one embodiment, the rear lens surface at the visual region of the lens body is configured such that the lens body at the visual region corresponds to a single lens. In another embodiment, the rear lens surface at the visual region of the lens body is configured such that the lens body at the visual region corresponds to a multifocal lens. In one embodiment, the rear lens surface at the visual region of the lens body is configured such that the lens body at the visual region corresponds to a convex lens. In one embodiment, the rear lens surface at the visual region of the lens body is configured such that the lens body at the visual region corresponds to a concave lens.

The present invention will be more clearly understood from the following description of the preferred embodiments of the invention.

The appended drawings are intended to illustrate one or more embodiments of the invention Wherever possible, the same element symbols are applied to all the drawings to represent the same or similar elements in the embodiments.

[Simple description of the map]

The first figure is a schematic view showing a pair of glasses with prescription parameters; the second figure is a schematic view showing a prescription lens according to an embodiment of the invention, wherein part (a) of the second figure is a top view, and Part (b) of the second figure is a side view; the third figure is a schematic view, wherein part (a) of the third figure is a lens blank, and part (b) of the third figure is an embodiment according to the present invention, a prescription lens made by a lens blank; the fourth figure is a schematic view showing a square lens according to an embodiment of the present invention; and the fifth figure is a schematic view showing a square lens according to another embodiment of the present invention; 6 is a schematic view showing a square lens according to another embodiment of the present invention; the seventh drawing is a schematic view showing a square lens according to still another embodiment of the present invention; (a) of the eighth figure is based on the present invention. A top view of a concave lens showing how to determine a coverage angle of 22 degrees, and part (b) of the eighth figure is a top view of a conventional concave lens; and a ninth diagram is a schematic view showing a conventional prescription. lens, FIG ninth of part (a) is a top view, and FIG ninth of part (b) is a side view.

The invention will be described more specifically with the following examples, as many modifications and variations will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail below. Referring to the drawings, the same reference numerals represent the same elements throughout the drawings. The meaning of "a" ("an", "an") and "the" (in the English specification) used in this document and throughout the scope of the patent application includes the plural. The meaning of the context, unless the contextual semantics are more clearly defined. Moreover, the meaning of "in" (in "in" in the English specification) as used herein and throughout the scope of the patent application includes "in" and "on" ( That is, "in" and "on" in English, unless the meaning of the context is more clearly defined.

The wording used in the specification generally has its ordinary meaning in the technical field, the scope of the invention, and the specific case in which each wording is used. With regard to the description of the invention, the specific language used to describe the invention is discussed later or elsewhere in the specification to provide additional guidance to the particular practitioner. The examples used in any part of the specification, including any examples of the words herein, are merely illustrative and are not intended to limit the scope and meaning of the invention or any examples. Also, the present invention is not limited to the various embodiments mentioned in the specification.

As used herein, "about" (referred to as "around", "about" or "approximately" in the English specification) generally means within 20% of the given value or range, preferably 100. Within ten points, and the best is less than five percent. The quantity given here is an approximate quantity, meaning that the word "about" can be inferred if there is no exact statement.

Embodiments of the present invention will be described in conjunction with the first to eighth figures attached hereinafter. In accordance with the purpose of the present invention, one aspect of the present invention relates to a prescription lens and a method of manufacturing the same, as generally described and hereinafter.

The first figure is a lens (110, 120) used in one of the pair of glasses having the lens (110, 120) prescription material (as specified in the prescription used by the wearer). The aforementioned prescription data includes the dimensions of the lens (110, 120) including height (H) and width (W); pupil distance (PD), which refers to the center of the pupil (114, 124) in the eye and the inner edge of the lens (110, 120). Distance (usually measured in millimeters); distance between lenses (DBL) refers to the distance between the inner edges of two lenses (110, 120); and optical center height (OCH). The lenses (110, 120) are sized to fit over the eyeglass frame and to select a suitable lens blank to create the lens (110, 120). The dimensional data of the lenses (110, 120) define the geometric center (112, 122) of the lenses (110, 120). In addition, the pupil distance (PD) defines the optical center (114, 124) of the lens (110, 120). The aforementioned prescription data also includes the lens power, the front base curve, the sphere power, the cylinder power, and the axial degree of each lens (110) or (120). (axis), distance vision (DV), and near vision (NV).

Please refer to the second figure, which is a top view (part (a) of the second figure) and a side view (part (b) of the second figure) of the concave lens (200) according to an embodiment of the present invention. The aforementioned prescription concave lens (200) has a ball front lens surface (216), a rear lens surface (218), and a lens defined between the ball front lens surface (216) and the rear lens surface (218). Body (210). The lens body (210) is characterized by a vision area (211), a transition area (213) surrounding the vision area (211), and an edge portion (215) surrounding the transition area (213). The visual area (211) is adapted to provide lens power based on the prescription of the lens used by the wearer. The thickness (Te) of the edge portion (215) is substantially the thickness of the lens that is substantially fixed and thinner than the visual area (211). The lens body (210) has a geometric center (212) and an optical center (214) corresponding to the center of the visual area (211). The optical center (214) is substantially offset from the geometric center (212). As shown in the fifth and seventh figures, the optical center (214) may also substantially coincide with the geometric center (212).

The ball front lens surface (216) is configured to mate with the frame curvature of the eyeglass frame. The rear lens surface (218) at the visual region (211) of the lens body (210) is configured such that the lens body (210) at the visual region (211) corresponds to a single lens. In one embodiment, the rear lens surface (218) at the visual region (211) of the lens body (210) is configured such that the lens body (210) at the visual region (211) is equivalent In a multifocal lens, the multifocal lens is a progressive lens or a bifocal lens.

Additionally, the rear lens surface (218) at the visual region (211) of the lens body (210) is configured such that the lens body (210) at the visual region (211) corresponds to a concave lens. In one embodiment, the rear lens surface (218) at the visual region (211) of the lens body (210) is configured such that the lens body (210) at the visual region (211) is equivalent In a convex lens, as shown in the sixth and seventh figures.

The prescription lens is formed from a transparent material such as glass or plastic.

The prescription lens (200) can be obtained by the following steps: firstly, obtaining the data of the prescription lens and the information of the eyeglass frame on which the prescription lens is mounted, wherein the data of the prescription lens includes at least the lens degree, the visual area and the base arc in front of the ball. And other information mentioned above. The material of the eyeglass frame includes frame curvature, which is characterized by the angle and inclination of the eyeglass frame. The ball front base arc of the prescription lens is adapted to match the frame curvature of the eyeglass frame. Measuring the frame angle of the eyeglass frame, for high arc curved coated sunglasses, the frame angle of the eyeglass frame can be up to 24 degrees. In addition, the wide-angle tilt of the eyeglass frame is also measured, or the wide-angle tilt of the eyeglass frame is estimated during lens calculation. In addition, the optical center height (OCH) or the distance above the bottommost portion of the eyeglass frame is also required.

Thereafter, the lens angle as a function of various eyeglass frames is determined in conjunction with the pupil distance, the frame angle, and the selected lens front curvature. Once the lens angle is known, the shaft compensation can be made.

The degree of spherical mirror and the degree of cylindrical mirror change due to the high arc bending coverage angle are measured. The angle required for the lenticule, as well as the changes required for the spherical power and the cylindrical power, are compensated so that the patient can feel the same spherical and cylindrical power as indicated by the prescription. The pupil distance (PD) is also compensated so that the optical center is directly aligned to the patient's pupil position. All calculations are taken into account to calculate the actual lens vision correction.

Thereafter, based on the data of the prescription lens, the maximum thickness of the lens of the prescription lens at the visual area is calculated. The aforementioned calculation steps are performed by a lens design software developed by Advanced Lens Technologies, LLC. The software is specifically designed to handle patient prescriptions and eyeglass frame materials, while the selection of lens blanks enables the creation of personalized lenses for customers. In one embodiment, the edge thickness and edge thinness of the lens are determined by compensating the posterior surface of the prescription lens and the optical zone, transition zone, and outer zone before determining the optical zone, the transition zone, and the outer zone. The thickness of the visual area depends on the thickness of the result.

One of the advantages of the present invention is that the desired maximum thickness of the lens is determined by the combined or individual values of the prescription. For example: a -4.00 spherical mirror combined with a 0.75 cylinder, and the maximum thickness of the lens with an 80 degree axis can be calculated according to the following equation: the maximum thickness of the lens = the degree of spherical mirror, or the maximum thickness of the lens = (spherical degree + cylindrical degree). The optical zone can be selected depending on the diameter of the optical zone or other predetermined shape. This will be used as the maximum thickness of the lens at the edge of the selected optical zone in a concave lens. For example, the thickness of the lens can be set to the degree of spherical mirror + the degree of cylindrical mirror = the maximum thickness of the lens is 5 mm. After that, the maximum size of the optical zone is calculated.

Once the maximum size of the optical zone is known, the dimensions of the transition zone and the outer zone can be calculated. The transition zone can be predetermined to a size of, for example, 5 mm, or the size of the transition zone can be varied depending on the lens of different thicknesses and the desired appearance.

Part (a) of Figure 8 is a top plan view of a square lens (810) in accordance with an embodiment of the present invention showing how a wrap angle of about 22 degrees is measured. Part (b) of the eighth figure is a top view of a conventional concave lens (820) in which the side profile of the prescription lens (810) is also shown for comparison. As is clear from the figure, the edge thickness of the prescription lens (810) is much thinner than the edge thickness of the conventional concave lens (820).

Based on the calculated maximum thickness of the lens at the visual area, the data of the prescription lens, and the data of the eyeglass frame, the lens blank (201) as shown in part (a) of the third figure is selected.

Processing the selected lens to obtain a prescription lens (200) having a transition zone (213) surrounding the visual zone (211) and an edge portion (215) surrounding the transition zone (213), such that the edge portion (215) The thickness (Te) is substantially thinner than the maximum thickness of the lens at the visual area (211).

The selected lenses can be finished lenses or semi-finished lenses. As shown in part (a) of the third figure, in the case of a finished lens, the processing step is accomplished by ejecting, casting, and cutting the edge portion (217) of the finished lens such that the thickness of the edge portion is substantially The maximum thickness of the lens that is fixed and thinner at the visual area. In accordance with the present invention, for finished lenses having a blend zone and an outer zone, the backside mold for the finished lens is very different from the conventional backside mold for finished lenses. The manufacturing method of the present invention is capable of producing lenses having a larger degree of myopia and a higher degree of farsight and having an optical zone, a mixing zone, and an outer zone. Conventional injection or casting lenses used in backside molds are only made to contain prescriptions but are not provided with mixing zones or other areas.

In the case of a semi-finished lens, the processing step is accomplished by turning a predetermined area of the semi-finished lens to form a visual area therein and cutting the edge portion of the semi-finished lens such that the thickness of the edge portion is fixed and substantially The maximum thickness of the lens that is thinner than the visual area.

A lens that is most suitable for a frame of sunglasses is manufactured using a method of manufacturing a sunglass lens at the surface of the lens in front of the ball. The invention is not limited to sunglasses lenses, but encompasses any prescription lens that has a front base curve and frame curvature. The present invention recognizes that a limited number of prescriptions will use a suitable front lens base arc and a matching frame curvature, whereas conventional methods of making these prescription lenses do not compensate for the tilting or cladding curvature of the sunglasses frame. The present invention encompasses single-light finished lenses.

The present invention provides the advantages of appearance and increases the accuracy of optical correction. The present invention is a combination of the optimal appearance of a prescription lens and the accuracy of wearing a correction. When viewed from the front, the present invention exhibits a prescription sunglasses lens that is well suited for mounting an eyeglass frame, as is the case without a prescription lens. When viewed from the rear, the lenses produced by the present invention are much thinner than conventional lens manufacturing methods used today to make most prescription lenses.

Prescription sunglasses are currently being manufactured based on prescriptions. Once the prescription is known, the front spherical curve lens can be suggested. The calculations used to make the required prescriptions can then be determined. The manufacture of the lens can then begin. The greater the degree of myopia prescription lens, the more flat the front base curve of the lens is recommended.

For example, a negative prescription is a spherical mirror of -4.00, and a front base arc of 2.00 to 4.00 is conventionally recommended. In order to manufacture a lens with a front base curve of 2.00, the back surface curvature must be 6.00. For lenses with a front base of 4.00, a back curvature of -8.00 is required to produce a prescription lens of -4.00. These two example lenses are cut to fit the eyeglass frame. Almost all sunglasses frames are designed with a front base curve of 6 or a front base curve of 8 (a few of the recent eyeglass frames are designed to require a front base curve of 9). In order to install the lens with the incorrect base curvature in the base arc frame with the front curvature of 6 or 8, the lens will have a part of the prescription lens not accurately matching the front arc of the ball, but with the inclination of the prescription lens. The lens can be mounted in an unsuitable front base curved eyeglass frame.

The solution provided by the present invention is that the present invention can produce a prescription lens that is almost completely matched with the frame curvature. In order to achieve this goal, it has been developed to produce a prescription lens that allows the patient to see more clearly, and data that is not currently considered to be used in the manufacture of prescription lenses for sunglasses must be considered.

A small number of optical professionals who manufacture prescription lenses have changed the prescription, taking into account the frame wrap and wide angle tilt. Such a change allows the wearer of the lens to see what the wearer sees as a conventional prescription lens that is made to fit the face. The difference provided by the present invention under the condition that the coating is changed with the inclination is that with the method for manufacturing the sunglasses lens, the prescription of the lens is adjusted to normal vision as in the wearing department, and the front base arc system and The glasses frame is matched.

The present invention creates a lens that looks like a patient when viewed from the front and does not look different from the over-the-counter lens. The optics of the lens are also adjusted by the present invention so that the use of a prescription that is compatible with the eyeglass frame and that is not a conventional front base arc can produce an appropriate effect.

The invention can produce a more suitable and more beautiful lens in terms of myopia and farsightedness. This advantage is based on the development of a patented prescription lens based on the frame angle and inclination, regardless of the patient's actual eyeglass frame shape. The visual area of the lens may not extend to all portions of the eyeglass frame. In order to create a lens that the patient can see and that fits the eyeglass frame, we must create a lens area that fits the lens and make the prescription lens as thin as possible and can be used for our chosen range of vision.

The optical center and geometric center are not located in the middle of the lens. The geometric center is the center of the circular lens, and the optical center is located 4 to 10 mm from the geometric center. As such, the lens covers the eyeglass frame with the optical center in front of the patient's eye.

An important aspect of the present invention is the calculation of the thinnest lens that will still give the patient an excellent area of the lens that has been optically corrected for its prescription. In order to calculate an optimized lens, we first need to know the patient's prescription information. We also need information on the glasses frame. In addition, the contour of the eyeglass frame or other methods for knowing the shape of the eyeglass frame are also required. Target lenses of different thicknesses are produced according to the prescription. For example, a lens with a -5.00 spherical mirror and a base arc of 8 will create a lens that will produce a thicker edge. After the lens is optimized with the frame data including the frame angle and the frame tilt, our software will calculate the prescription. Assuming that the ideal lens has a maximum thickness of 4.5 mm, the maximum thickness of the lens in the visual area described by the software is 4.5 mm. Any area greater than 4.5 mm thick will be an optically corrected area, and areas greater than 4.5 mm thick will only be used to make additional lenses that need to be properly matched to the eyeglass frame, resulting in a good visual result when the patient is wearing it. The area, but looks like the aesthetic design of the over-the-counter lens.

The present invention has been described by way of illustration only and not by way of limitation. Various modifications and changes made in light of the above teachings are within the scope of the invention.

The specific embodiments were chosen and described in order to explain the embodiments of the invention, Various alternative embodiments that are within the spirit and scope of the invention will be apparent to those skilled in the art. Therefore, the scope of the invention is defined by the scope of the appended claims, rather than the

110. . . lens

112. . . Geometric center

114. . . Optical center

120. . . lens

122. . . Geometric center

124. . . Optical center

200. . . Prescription lens

201. . . Lens blank

210. . . Lens body

211. . . Visual area

212. . . Geometric center

213. . . Transition zone

214. . . Optical center

215. . . Edge portion

216. . . Lens surface in front of the ball

217. . . Edge portion

218. . . Rear lens surface

400. . . Prescription lens

412. . . Geometric center

414. . . Optical center

500. . . Prescription lens

512. . . Geometric center

514. . . Optical center

600. . . Prescription lens

700. . . Prescription lens

810. . . Prescription lens

820. . . Traditional concave lens

900. . . concave lens

910. . . Lens surface

920. . . edge

DBL. . . Distance between lenses

H. . . height

OCH. . . Optical center height

PD. . . Pupil distance

Te. . . thickness

To. . . Maximum thickness

W. . . width

The first figure is a schematic diagram showing a pair of glasses with prescription parameters;

The second drawing is a schematic view showing a prescription lens according to an embodiment of the present invention, wherein part (a) of the second figure is a top view, and part (b) of the second figure is a side view;

The third figure is a schematic diagram, wherein part (a) of the third figure is a lens blank, and part (b) of the third figure is a prescription lens made from the lens blank according to an embodiment of the invention;

The fourth figure is a schematic view showing a square lens according to an embodiment of the present invention;

Figure 5 is a schematic view showing a square lens according to another embodiment of the present invention;

Figure 6 is a schematic view showing a square lens according to still another embodiment of the present invention;

Figure 7 is a schematic view showing a square lens according to still another embodiment of the present invention;

Part (a) of the eighth embodiment is a top view of a concave lens according to an embodiment of the present invention, showing how to determine a coverage angle of 22 degrees, and part (b) of the eighth figure is a top view of a conventional concave lens; as well as

The ninth drawing is a schematic view showing a conventional prescription lens, wherein part (a) of the ninth drawing is a top view, and part (b) of the ninth drawing is a side view.

200. . . Prescription lens

210. . . Lens body

211. . . Visual area

212. . . Geometric center

213. . . Transition zone

214. . . Optical center

215. . . Edge portion

216. . . Arc lens surface in front of the ball

218. . . Rear arc lens surface

Te. . . thickness

Claims (13)

A prescription lens comprising: (a) a front surface of a lens having a front base arc configured to conform to a curvature fit of the eyeglass frame; (b) a rear lens surface; and (c) a lens body from which the spherical front Defining between a lens surface and the rear lens surface, wherein the lens body is characterized by a vision area, a transition area surrounding the vision area, and an edge portion surrounding the transition area, and the rear lens surface Having a curvature in the visual region whereby the visual region of the lens body has a lens degree conforming to a prescription of the wearer, the rear lens surface being a plane at the edge portion and perpendicular to the optical axis of the lens body, the rear lens The surface has a curvature in the transition zone that connects the visual area and the edge portion. The lens according to claim 1, wherein the lens body has a geometric center and an optical center corresponding to a center of the vision area. A square lens as claimed in claim 2, wherein the optical center substantially coincides with the geometric center. A square lens as described in claim 2, wherein the optical center is substantially offset from the geometric center. The lens according to claim 1, wherein the rear lens surface located at the visual region of the lens body is configured such that the lens body located at the visual region corresponds to a single lens. The square lens according to claim 1, wherein the rear lens surface located at the visual area of the lens body is configured as a bit The lens body at the visual area corresponds to a multifocal lens, which is a progressive lens or a bifocal lens. The lens according to claim 1, wherein the rear lens surface located at the visual region of the lens body is configured such that the lens body located at the visual region corresponds to a convex lens. The lens according to claim 1, wherein the rear lens surface located at the visual region of the lens body is configured such that the lens body located at the visual region corresponds to a concave lens. The square lens formed in the first aspect of the patent application includes the glass or plastic material forming the prescription lens. The square lens as described in claim 9 is formed by injecting or pouring the material of the prescription lens into a back mold. A lens comprising: (a) a front surface of a lens having a front base arc conforming to a frame curvature of the eyeglass frame; (b) a curved rear lens surface having a visual area and a surrounding a transition region of the visual region, and an edge portion surrounding the transition region; wherein the rear lens surface has an arc in the visual region, whereby the visual region of the lens has a lens power that conforms to a wearer's prescription, The rear lens surface is a plane perpendicular to the optical axis of the lens at the edge portion, the lens having a uniform thickness surrounding the periphery of the lens, the edge thickness being less than the thickness of the visual region, the rear lens surface having the transition region An arc is smoothly connected to the visual area and the plane of the edge portion. The lens of claim 11, wherein the front base curve is 6-8. The lens of claim 11, wherein the lens has a 22 degree coverage angle.