Optimization design method for rigid gas permeable contact lens and rigid gas permeable contact lens

Abstract

The present disclosure relates to an optimization design method for a rigid gas permeable contact lens and a rigid gas permeable contact lens. The method comprises: acquiring a lens front surface original included angle, the lens front surface original included angle being used for representing an included angle, determined on the basis of lens prescription parameters, between two adjacent arc segments on the front surface of a lens; determining whether the lens front surface original included angle needs to be optimized; and if the lens front surface original included angle needs to be optimized, dividing at least one target arc segment among the two adjacent arc segments participating in forming the lens front surface original included angle into a first number of sub-arc segments, and allocating the width and sagittal height of the target arc segment to the first number of sub-arc segments with the objectives that a lens front surface new included angle is closer to 180° than the lens front surface original included angle, the width of any sub-arc segment is greater than or equal to a first threshold, and an included angle between any two adjacent sub-arc segments ranges from 170° to 190°. Therefore, by optimizing the lens front surface original included angle of the rigid gas permeable contact lens, the comfort can be improved.

Description

Optimization design methods for rigid gas permeable (RGP) contact lenses and RGP contact lenses

[0001] This disclosure claims priority to Chinese Patent Application No. 202411922106.7, filed on December 25, 2024, entitled "Optimization Design Method for Rigid Corneal Contact Lenses and Rigid Corneal Contact Lenses". Technical Field

[0002] This disclosure relates to the field of rigid gas permeable contact lenses, and in particular to the optimized design of the anterior surface of rigid gas permeable contact lenses. Background Technology

[0003] In the field of refractive correction and myopia control, rigid gas permeable (RGP) contact lenses hold a prominent position due to their unique advantages. RGP lenses offer superior visual performance, excelling in vision correction and providing wearers with clear, sharp vision. Furthermore, by providing excellent tear and oxygen exchange, wearing RGP lenses is beneficial for corneal health. However, RGP lenses are often less accepted in the market than soft lenses. One significant reason is the difference in comfort. Soft lenses are softer and conform better to the eyeball, generally providing a more comfortable wearing experience. RGP lenses, due to their relatively harder material, may cause a foreign body sensation or even pain during initial wear, which has somewhat hampered their market adoption.

[0004] Therefore, comfort is paramount for rigid contact lenses. Only by continuously improving the comfort of rigid contact lenses can more people be willing to choose them as a tool for refractive correction and myopia control. To achieve this goal, the industry is constantly exploring and trying various methods to improve comfort. Summary of the Invention

[0005] One objective of this disclosure is to optimize the front surface of rigid gas permeable contact lenses to improve comfort.

[0006] According to a first aspect of this disclosure, an optimized design method for a rigid gas permeable contact lens is provided, comprising: obtaining the original angle of the anterior surface of the lens, the original angle of the anterior surface of the lens being used to characterize the angle between two adjacent arc segments on the anterior surface of the lens determined based on lens prescription parameters; determining whether the original angle of the anterior surface of the lens needs to be optimized; if the original angle of the anterior surface of the lens needs to be optimized, then splitting at least one target arc segment among the two adjacent arc segments involved in forming the original angle of the anterior surface of the lens into a first number of sub-arc segments, and aiming to make the new angle of the anterior surface of the lens closer to 180° than the original angle of the anterior surface of the lens, the width of any sub-arc segment being greater than or equal to a first threshold, and the angle between any two adjacent sub-arc segments being between 170° and 190°, and allocating the width and sag of the target arc segment to the first number of sub-arc segments.

[0007] Optionally, the original included angle of the front surface of the lens is the angle between the end of the optical region of the front surface of the lens and the beginning of the peripheral region of the front surface of the lens. Dividing at least one target arc segment of the two adjacent arc segments that participate in forming the original included angle of the front surface of the lens into a first number of sub-arc segments includes: dividing the peripheral region of the front surface of the lens into a first number of sub-regions, each sub-region corresponding to a sub-arc segment.

[0008] Optionally, the first number is 3 to 12, with different sub-arc segments having the same width. If the original included angle of the front surface of the lens is greater than 180°, the sagitta of the first number of sub-arc segments is arranged in a decreasing arithmetic sequence from the inside to the outside. If the original included angle of the front surface of the lens is less than 180°, the sagitta of the first number of sub-arc segments is arranged in an increasing arithmetic sequence from the inside to the outside. The difference d of the arithmetic sequence satisfies... Where N is equal to the first quantity.

[0009] Optionally, the first quantity is positively correlated with the absolute value of the difference between the original angle between the front surface of the lens and 180°.

[0010] Optionally, the original included angle of the front surface of the lens is between 170° and 190°, the first quantity is 2, and different sub-arc segments have the same width. If the original included angle of the front surface of the lens is greater than 180°, the proportion of the sag of the sub-arc segment relatively close to the center of the lens is 61.8%, and the proportion of the sag of the sub-arc segment relatively close to the edge of the lens is 38.2%. If the original included angle of the front surface of the lens is less than 180°, the proportion of the sag of the sub-arc segment relatively close to the center of the lens is 38.2%, and the proportion of the sag of the sub-arc segment relatively close to the edge of the lens is 61.8%.

[0011] Optionally, the original included angle of the front surface is less than 170° or greater than 190°, and the absolute value of the difference between the original included angle of the front surface and 180° is less than a predetermined threshold. The first quantity is 3, and different sub-arc segments have the same width. If the original included angle of the front surface is greater than 180°, the proportion of the sagitta of the sub-arc segment closest to the center of the lens is 42% to 52%, the proportion of the sagitta of the middle sub-arc segment is 30% to 36%, and the proportion of the sagitta of the sub-arc segment closest to the edge of the lens is 18% to 22%. If the original included angle of the front surface is less than 180°, the proportion of the sagitta of the sub-arc segment closest to the center of the lens is 18% to 23%, the proportion of the sagitta of the middle sub-arc segment is 31% to 36%, and the proportion of the sagitta of the sub-arc segment closest to the edge of the lens is 41% to 51%.

[0012] Optionally, assigning the width and elevation of the target arc segment to the first number of sub-arc segments includes: determining the width and elevation of each sub-arc segment based on the following formula.

[0013] Where r(n) is the radius of curvature of the nth sub-arc segment, S n Let d be the sag of the nth sub-arc segment. n-1 Let d be the inner diameter of the nth sub-arc segment. n Let A(n) be the outer diameter of the nth sub-arc segment, and let A(n) be the angle between the nth and (n+1)th sub-arc segments. n+1 Let be the radius of curvature of the (n+1)th sub-arc segment.

[0014] Optionally, the method further includes: obtaining coordinate parameters of each sub-arc segment, the coordinate parameters including start end coordinates and end end coordinates; inputting the coordinate parameters of each sub-arc segment into a CNC machining equipment in the form of a queue, and programming it according to the coaxial circular interpolation method, so that the machining equipment completes the lens machining task through coaxial circular interpolation.

[0015] Optionally, the method further includes: drawing a path diagram of the optimized lens design, and submitting the path diagram to a CNC machining equipment for lens processing.

[0016] Optionally, the method further includes: hydrophilizing the surface of the lens material; and / or using a lens material with higher oxygen permeability; and / or thinning the lens edge.

[0017] According to a second aspect of this disclosure, a rigid gas permeable contact lens is provided, comprising a lens body, wherein a target arc segment on the anterior surface of the lens body is divided into a first number of sub-arc segments, the target arc segment being at least one of two adjacent arc segments participating in forming the original included angle of the anterior surface of the lens, the original included angle of the anterior surface being the included angle of the anterior surface before optimization, and the new included angle of the anterior surface of the lens formed after the division being closer to 180° than the original included angle of the anterior surface of the lens, wherein the width of any sub-arc segment is greater than or equal to a first threshold, and the included angle between any two adjacent sub-arc segments is between 170° and 190°.

[0018] Optionally, the original included angle of the front surface of the lens is the included angle between the end of the optical region of the front surface of the lens and the beginning of the peripheral region of the front surface of the lens, and the target arc segment is the arc segment corresponding to the peripheral region of the front surface of the lens.

[0019] Optionally, different sub-arcs have the same width but different sags.

[0020] Optionally, the first number is 3 to 12. If the original included angle of the front surface of the lens is greater than 180°, the sagitta of the first number of sub-arc segments are arranged in a decreasing arithmetic sequence from the inside to the outside. If the original included angle of the front surface of the lens is less than 180°, the sagitta of the first number of sub-arc segments are arranged in an increasing arithmetic sequence from the inside to the outside. The difference d of the arithmetic sequence satisfies the following condition: Where N is equal to the first quantity.

[0021] Optionally, the first quantity is positively correlated with the absolute value of the difference between the original angle between the front surface of the lens and 180°.

[0022] Optionally, the original included angle of the front surface of the lens is between 170° and 190°, and the first quantity is 2. If the original included angle of the front surface of the lens is greater than 180°, the proportion of the sag of the sub-arc segment relative to the center of the lens is 61.8%, and the proportion of the sag of the sub-arc segment relative to the edge of the lens is 38.2%. If the original included angle of the front surface of the lens is less than 180°, the proportion of the sag of the sub-arc segment relative to the center of the lens is 38.2%, and the proportion of the sag of the sub-arc segment relative to the edge of the lens is 61.8%.

[0023] Optionally, the original included angle of the front surface is less than 170° or greater than 190°, and the absolute value of the difference between the original included angle of the front surface and 180° is less than a predetermined threshold. The first quantity is 3. If the original included angle of the front surface is greater than 180°, the proportion of the sagitta of the sub-arc segment closest to the center of the lens is 42% to 52%, the proportion of the sagitta of the middle sub-arc segment is 30% to 36%, and the proportion of the sagitta of the sub-arc segment closest to the edge of the lens is 18% to 22%. If the original included angle of the front surface is less than 180°, the proportion of the sagitta of the sub-arc segment closest to the center of the lens is 18% to 23%, the proportion of the sagitta of the middle sub-arc segment is 31% to 36%, and the proportion of the sagitta of the sub-arc segment closest to the edge of the lens is 41% to 51%.

[0024] Optionally, the first threshold is 0.2 mm.

[0025] Optionally, the included angle between any two adjacent sub-arc segments is between 176° and 184°.

[0026] Optionally, the width and sag of each of the sub-arc segments are determined based on the following formula:

[0027] Where r(n) is the radius of curvature of the nth sub-arc segment, S n Let d be the sag of the nth sub-arc segment. n-1 Let d be the inner diameter of the nth sub-arc segment. n Let A(n) be the outer diameter of the nth sub-arc segment, and let A(n) be the angle between the nth and (n+1)th sub-arc segments. n+1 Let be the radius of curvature of the (n+1)th sub-arc segment.

[0028] To optimize the original angle of the lens anterior surface, this disclosure divides at least one target arc segment from two adjacent arc segments forming the original angle into a first number of sub-arc segments. The target is to make the new angle of the lens anterior surface closer to 180° than the original angle, with the width of any sub-arc segment greater than or equal to a first threshold, and the angle between any two adjacent sub-arc segments between 170° and 190°. The width and sag of the target arc segment are then allocated to the first number of sub-arc segments. This provides a simple, easy, and highly effective way to optimize the design of the lens anterior surface angle, thereby improving the comfort of wearing rigid gas permeable (RGP) contact lenses. Attached Figure Description

[0029] The above and other objects, features and advantages of this disclosure will become more apparent from the more detailed description of exemplary embodiments thereof taken in conjunction with the accompanying drawings, wherein like reference numerals generally denote like parts.

[0030] Figure 1 shows a flowchart of an optimized design method for a rigid gas permeable contact lens according to an embodiment of the present disclosure.

[0031] Figures 2 and 3 show schematic diagrams of the included angle of the front surface of the lens.

[0032] Figures 4 and 5 show schematic diagrams of optimizing the included angle of the front surface of the lens using three sub-arcs. Detailed Implementation

[0033] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0034] The discomfort when wearing contact lenses mainly comes from the impact and friction between the eyelids, cornea and lens when blinking.

[0035] When you blink, your eyelids move relative to the lens, and the lens also moves to some extent on the surface of the cornea.

[0036] This movement creates friction, just like a rough object rubbing against the skin, which can cause discomfort.

[0037] Especially the edges of the lenses, if poorly designed or not smooth enough, will cause the wearer to feel a foreign object sensation and experience strong discomfort when they frequently come into contact with and rub against the eyelids.

[0038] The commonly used methods for improving comfort include the following.

[0039] Firstly, the lens design has been optimized. A thinner, specially shaped edge design effectively reduces friction between the lens and the eyelid, thereby improving wearing comfort.

[0040] Secondly, improve the materials. Improve the hydrophilicity of the material surface to maximize comfort while maintaining the optical performance of rigid contact lenses.

[0041] Third, optimize lens fitting. By improving the geometric design of the lens fitting area, the movement of the lens on the cornea is reduced, thereby reducing friction between the lens and the cornea and eyelids, and reducing wearing discomfort.

[0042] Fourth, use auxiliary medical devices or drugs such as lubricants to provide buffering and lubrication between the lens and the eyelid and cornea, while strengthening tear circulation, protecting corneal health and reducing discomfort.

[0043] While all four improvement methods have good effects, they also have their own drawbacks or limitations. Thinning the lens edge effectively reduces impact and friction between the eyelid and the lens edge; however, the space for thinning the lens edge is limited, and an excessively thin edge design significantly increases manufacturing difficulty, making the lens more prone to edge damage during wear and maintenance. Improving hydrophilicity makes the lens surface smoother, reducing friction and stickiness when blinking. Plasma hydrophilic coatings have become a standard feature of rigid contact lenses, but their durability still needs improvement. Adjusting the lens fit reduces lens movement, thereby reducing friction with the cornea and eyelids, but it also reduces tear and oxygen exchange, which is detrimental to corneal health. Lubricating fluids and other auxiliary methods are effective, but their durability is worse, and they increase the wearer's usage costs.

[0044] Furthermore, while these four methods can be used in combination, they can also be mutually restrictive. Currently, rigid contact lenses on the market typically consider and balance these four improvement methods to achieve optimal comfort.

[0045] In summary, while rigid gas permeable (RGP) contact lenses offer advantages in visual quality and corneal health, their lack of comfort limits their market acceptance. Continuous exploration and application of comfort improvement methods hold promise for enhancing the comfort of RGP lenses and enabling them to play a greater role in the vision correction market.

[0046] This disclosure provides a novel method for improving the comfort of rigid contact lenses. This method is simple to implement and requires no technical expertise. Furthermore, this method can be used independently or in conjunction with four other methods, making it easier to achieve a balance between comfort, safety, and visual effects in rigid contact lenses.

[0047] This disclosure, based on research, reveals that the sharp angles of the anterior surface are one of the main causes of eyelid discomfort, especially with lenses having large positive or negative powers, or multifocal lenses used for presbyopia correction or myopia control; this sensation is more pronounced in these lenses. Such sharp angles are an inherent problem with rigid contact lenses, determined by the basic optical principles of lenses. Since the refractive power of a lens is primarily determined by the radii of curvature of its anterior and posterior surfaces, lenses with extreme powers exhibit significant thickness differences between the center and periphery, resulting in sharp angles. Furthermore, regional multifocal lenses also produce varying degrees of sharp angles between regions due to differences in power.

[0048] Regardless of their shape, the sharp edges of the lens's front surface can scratch the eyelids, and even cause the lens to get stuck or lift up when moving, resulting in a foreign body sensation or even stinging, greatly affecting the comfort of wearing the lens. This published study found that the human eye is highly sensitive to angles; the closer the angle between two arcs is to 180°, the lower the discomfort during wear. When the angle is less than 176° or greater than 184°, the human eye can clearly feel the presence of the lens, while when the angle is less than 170° or greater than 190°, a clear discomfort is felt. Polishing the lens's front surface can improve this problem to some extent, but its limitations are also obvious. Polishing cannot handle more extreme angles, and excessive polishing can seriously damage the lens's most important optical properties. Therefore, optimizing the design of the lens's front surface angle is a simple, easy, and highly effective improvement method.

[0049] In this disclosure, the included angle of the lens front surface that needs to be optimized can refer to the angle between any two adjacent arc segments of the lens front surface. For a single-focal lens, there is usually only one included angle of the lens front surface that needs to be optimized (i.e., the angle between the edge of the optical region of the lens front surface and the peripheral region of the lens front surface). For a multifocal lens, there may be several included angles of the lens front surface that need to be optimized.

[0050] This disclosure also found through experiments that the outermost angle is more likely to cause discomfort. This is because the outermost angle comes into contact with the eyelid more frequently, and because the angle itself is caused by the difference in the radius of curvature of the front and back surfaces. The outermost angle has a stronger tailing effect, so the angle is more likely to be sharp.

[0051] Therefore, this disclosure focuses on optimizing the angles of the lens's front surface near the lens edge (e.g., the angle between the edge of the optical region of the lens's front surface and the peripheral region of the lens's front surface). The angles of the front surface near the lens center (e.g., the angles within the optical region of the lens's front surface) can be optimized or left unoptimized. For example, assuming a multifocal lens has angles at diameters of 1mm and 3mm, these angles, being close to the lens center, have minimal impact on comfort and therefore do not need optimization. Furthermore, optimizing the angle between the edge of the optical region of the lens's front surface and the peripheral region of the lens's front surface does not affect the lens's optical performance, thus improving comfort without compromising visual quality.

[0052] Figure 1 shows a flowchart of an optimized design method for a rigid gas permeable contact lens according to an embodiment of the present disclosure.

[0053] Referring to Figure 1, in step S110, the original included angle of the front surface of the lens is obtained.

[0054] The original included angle of the lens front surface refers to the angle between two adjacent arc segments on the lens front surface, determined according to the lens prescription parameters before the lens is optimized. The two adjacent arc segments that form the original included angle of the lens front surface can refer to any two adjacent arc segments on the lens front surface. That is, the included angle of the lens front surface can refer to the angle between any two adjacent arc segments on the lens front surface, determined based on the lens prescription parameters.

[0055] For ease of understanding, this disclosure defines a raised edge angle as less than 180° and a recessed edge angle as greater than 180°; that is, an edge angle is defined as the angle of a material cross-section. Figures 2 and 3 show schematic diagrams of the included angle of the front surface of a lens. In Figures 2 and 3, the included angle of the front surface of a lens refers to the angle between the end of the optical region of the front surface of the lens and the beginning of the peripheral region of the front surface of the lens. "End" and "beginning" refer to the end and beginning in the direction from the center of the lens outwards. The included angle of the front surface of the lens in Figure 2 is greater than 180°, meaning the included angle of the front surface of the lens in Figure 2 is a raised edge. The included angle of the front surface of the lens in Figure 3 is less than 180°, meaning the included angle of the front surface of the lens in Figure 3 is a recessed edge.

[0056] In this disclosure, "arc" is defined as a continuous circular arc / curve on the central cross-section of a lens. The earliest spectral and contact lenses were rotationally symmetric spherical designs, and the entire lens could be described by a cross-section passing through its central axis. This cross-section consisted of multiple circular arcs; therefore, continuous curved surfaces on the lens were also called "arcs" or "arc regions." Later, as lens surface designs became increasingly complex, aspherical surfaces, torus surfaces, and free-form higher-order surfaces emerged, whose cross-sections were not necessarily circular arcs, but the term "arc" was still used.

[0057] In some embodiments, the original included angle of the lens anterior surface can refer to the angle between the end of the optical region of the lens anterior surface and the beginning of the peripheral region of the lens anterior surface. That is, only the included angle outside the optical region of the lens anterior surface can be optimized. Optimizing the included angle (usually one) outside the optical region of the lens anterior surface can significantly improve comfort without affecting visual performance. The optical region is defined as the corresponding area through which external light rays passing through the region enter the pupil.

[0058] Once the lens prescription parameters (such as base curve radius, total diameter, and posterior vertex power) are determined, the lens shape is also determined, which is equivalent to the original angle of the lens's front surface being fixed. Based on the lens prescription parameters, Euclidean or analytical geometry methods, or analytical geometric modeling, can be used to analyze the lens cross-sectional shape and calculate the original angle of the lens's front surface, as well as the relevant parameters needed to optimize it. Taking the original angle of the lens's front surface as the angle between the end of the optical region on the front surface and the beginning of the peripheral region on the front surface as an example, the diameter, width, and sag of the peripheral region on the front surface that needs optimization, as well as the original angle of the front surface, can be calculated based on the prescription parameters as a reference.

[0059] The following example illustrates the principle of calculating the distance between two adjacent arc segments.

[0060] When the starting and ending diameters of an arc segment are known, as well as the difference in elevation between them, the radius of curvature of the arc segment can be calculated using Euclidean geometry, and the tangent directions at the starting and ending points can be deduced. For special surfaces (such as arc segments composed of conic sections), analytical geometry can be used to describe the cross-sectional profile of the lens using functional formulas, and the slopes at the starting and ending points can be calculated using derivatives, thus deducing the tangent directions at these two points.

[0061] According to analytic geometry, for any continuously differentiable function curve f(x), its derivative f'(x) represents its slope at point x, which is the tangent of the angle between the tangent line at that point and the x-axis. Therefore, the angle between this point and the x-axis is acrtan[f'(x)]. The angle between two adjacent arc segments is the angle between the two tangent lines at the junction of the two arc segments.

[0062] Taking a quadratic aspherical surface as an example, the analytical formula for the arc section is:

[0063] Where c is the curvature of the center vertex of the arc segment, K is the quadratic surface constant, and x is the distance from the central axis of the lens.

[0064] Taking the first derivative of formula (1), the result can be expressed as:

[0065] Substitute c and K of the arc segment into formula (2). Substituting x, which is half the diameter inside the arc region, into formula (2) yields the slope of the tangent at the beginning of the arc segment. Substituting x, which is half the diameter outside the arc region, into formula (2) yields the slope of the tangent at the end of the arc segment.

[0066] Assuming the arc segment has c = 0.125, K = -0.25, and x = 3 at its end, then f'(3) = 0.397. Also, arctan[f'(3)] = 0.377 rad, meaning the angle between the end of the arc segment and the x-axis is 21.6°. Similarly, the angle between the starting point of the next arc segment connected to the end of this arc segment and the x-axis can be calculated, assuming it to be 35°. Therefore, the angle between these two adjacent arc segments is 180° + 21.6° - 35° = 166.6°, which is a convex angle that needs optimization.

[0067] In step S120, it is determined whether the original included angle of the front surface of the lens needs to be optimized.

[0068] In some implementations, optimization may be performed only on the lens front surface angle that is less than 170° or greater than 190°. That is, the lens front surface angle is determined to need optimization only when it is less than 170° or greater than 190°.

[0069] In other embodiments, if the original included angle of the front surface of the lens is already within the range of 170° to 190° (but not equal to 180°), it can also be optimized. That is, as long as the original included angle of the front surface of the lens is not equal to 180°, it can be optimized so that the optimized new included angle of the front surface of the lens is closer to 180° than the original included angle of the front surface of the lens.

[0070] In step S130, if the original included angle of the front surface of the lens needs to be optimized, at least one target arc segment among the two adjacent arc segments that participate in forming the original included angle of the front surface of the lens is divided into a first number of sub-arc segments. The goal is to make the new included angle of the front surface of the lens closer to 180° than the original included angle of the front surface of the lens, the width of any sub-arc segment is greater than or equal to a first threshold, and the included angle between any two adjacent sub-arc segments is between 170° and 190°. The width and sag of the target arc segment are then assigned to the first number of sub-arc segments.

[0071] The following example, using the original included angle of the lens's front surface as the angle between the end of the optical region on the front surface and the beginning of the peripheral region on the front surface, illustrates the specific optimization process. It should be understood that when the original included angle of the lens's front surface is an angle within the optical region of the front surface (such as the angle between regions of different focal powers), the optimization process described below can also be used (and can be combined with other methods to optimize the angle while minimizing the impact on the lens's optical performance).

[0072] The latter of the two adjacent arc segments that contribute to forming the original included angle on the front surface of the lens (i.e., the arc segment corresponding to the peripheral area of ​​the front surface) can be divided into a first number of sub-arc segments. Dividing the arc segment corresponding to the peripheral area of ​​the front surface into a first number of sub-arc segments is equivalent to dividing the peripheral area of ​​the front surface into a first number of sub-regions, each sub-region corresponding to one sub-arc segment. Optimizing the design of the arc segment corresponding to the peripheral area of ​​the front surface does not affect the optical performance of the lens, thus improving comfort without compromising visual quality.

[0073] If the width of a single sub-arc segment is too small, it will be difficult to achieve the effect of optimizing the original included angle of the lens's front surface by splitting the arc segments, and the processing difficulty will be high. Therefore, the width of a single sub-arc segment should be greater than or equal to a first threshold. For example, the first threshold can be equal to 0.2 mm. The widths of different sub-arc segments can be evenly or unevenly distributed. That is, the widths of different sub-arc segments can be the same or different. The sag of different sub-arc segments is not evenly distributed, but can be distributed with the goal of making the new included angle of the lens's front surface closer to 180° compared to the original included angle of the lens's front surface, and the included angle between any two adjacent sub-arc segments between 170° and 190°.

[0074] The angle between two adjacent sub-arc segments is functionally related to the width and height of these two sub-arc segments. Therefore, the width and height of these sub-arc segments can be assigned according to this functional relationship to optimize the original angle of the lens's front surface. Specifically, based on this functional relationship, the width and height of each sub-arc segment can be determined with the goal of making the new angle of the lens's front surface closer to 180° compared to the original angle, ensuring that the width of any sub-arc segment is greater than or equal to a first threshold, and that the angle between any two adjacent sub-arc segments is between 170° and 190°. The sum of the widths of all sub-arc segments equals the width of the peripheral region of the lens's front surface. The sum of the heights of all sub-arc segments equals the height of the peripheral region of the lens's front surface.

[0075] The functional relationship between the included angle between two adjacent sub-arc segments and the width and sag of these two sub-arc segments can be expressed as follows:

[0076] Formula (3) is the formula for calculating the radius of curvature of a sub-arc segment, and formula (4) is the formula for calculating the angle between two adjacent sub-arc segments. r(n) is the radius of curvature of the nth sub-arc segment, and S... n Let d be the sag of the nth sub-arc segment. n-1 Let d be the inner diameter of the nth sub-arc segment. n Let A(n) be the outer diameter of the nth sub-arc segment, and let A(n) be the angle between the nth and (n+1)th sub-arc segments. n+1Let be the radius of curvature of the (n+1)th sub-arc segment. The width of a given arc segment is equal to the outer diameter minus the inner diameter. The outer diameter of a sub-arc segment is the diameter of the circle centered at the lens center and with the outer edge of the sub-arc segment as its boundary line. The outer diameter can also be called the diameter of the outer edge. The inner diameter of a sub-arc segment is the diameter of the circle centered at the lens center and with the inner edge of the sub-arc segment as its boundary line. The inner diameter can also be called the diameter of the inner edge.

[0077] Based on the above formulas (3) and (4), the diameter (i.e., width) and sag of each sub-arc segment can be allocated to ensure that the included angle between adjacent sub-arc segments is within a reasonable range. The reasonable range can be between 170° and 190°. Preferably, it can be between 176° and 184°. That is to say, the width and sag of each sub-arc segment can be determined based on the above formulas (3) and (4).

[0078] The new included angle of the front surface of the lens refers to the angle between the end of the optical region of the front surface of the lens and the first sub-arc segment. The new included angle of the front surface of the lens can be calculated with reference to the above formulas (3) and (4). Among them, the arc segment corresponding to the optical region of the front surface of the lens can be regarded as the front sub-arc segment, and the first sub-arc segment can be regarded as the rear sub-arc segment.

[0079] In this disclosure, the first number can be determined by the degree to which the original included angle of the lens anterior surface deviates from 180° as needed for optimization. Generally speaking, the greater the degree to which the original included angle of the lens anterior surface deviates from 180°, the larger the first number will be. That is, by dividing the peripheral region of the lens anterior surface into a large number of sub-arc segments, the included angle at any extreme degree can be improved.

[0080] Implementation Method 1

[0081] The initial number can be 3 to 12, preferably 3 to 9. Different sub-arc segments have the same width.

[0082] If the original included angle of the front surface of the lens is greater than 180°, the sagitta of the first number of sub-arc segments are arranged in a decreasing arithmetic sequence from the inside to the outside. If the original included angle of the front surface of the lens is less than 180°, the sagitta of the first number of sub-arc segments are arranged in an increasing arithmetic sequence from the inside to the outside.

[0083] The difference d of an arithmetic sequence satisfies, Where N equals the first quantity.

[0084] This method can be used to improve angles at any extreme degree. The more arc segments used, the better the improvement, but the computational load is also relatively higher, without affecting the processing difficulty or efficiency. For example, the first quantity is positively correlated with the absolute value of the difference between the original angle of the lens's front surface and 180°. That is, the larger the absolute value of the difference between the original angle of the lens's front surface and 180° (i.e., the more the original angle of the lens's front surface deviates from 180°), the larger the first quantity can be set.

[0085] Implementation Method 2

[0086] The first quantity can be 2. Different sub-arcs can have the same width.

[0087] If the original included angle of the front surface of the lens is greater than 180°, the proportion of the sag of the sub-arc segment relatively closer to the center of the lens is 61.8%, and the proportion of the sag of the sub-arc segment relatively closer to the edge of the lens is 38.2%.

[0088] If the original included angle of the front surface of the lens is less than 180°, the proportion of the sag of the sub-arc segment relatively close to the center of the lens is 38.2%, and the proportion of the sag of the sub-arc segment relatively close to the edge of the lens is 61.8%.

[0089] Sagittal ratio is used to characterize the proportion of the sagittal of a sub-arc segment to the sagittal of the peripheral area of ​​the front surface of the lens.

[0090] This method is suitable for lenses where the need for improvement in the original angle of the lens's front surface is not very high, such as when the original angle of the lens's front surface is already in the range of 170° to 190°, but the wearer wants to further improve it.

[0091] Implementation Method 3

[0092] The first quantity can be 3. Different sub-segments can have the same width.

[0093] If the original included angle of the front surface is greater than 180°, the proportion of the sagitta of the sub-arc segment closest to the center of the lens is 42% to 52%, the proportion of the sagitta of the middle sub-arc segment is 30% to 36%, and the proportion of the sagitta of the sub-arc segment closest to the edge of the lens is 18% to 22%.

[0094] If the original included angle of the front surface is less than 180°, the proportion of the sagitta of the sub-arc segment closest to the center of the lens is 18% to 23%, the proportion of the sagitta of the middle sub-arc segment is 31% to 36%, and the proportion of the sagitta of the sub-arc segment closest to the edge of the lens is 41% to 51%.

[0095] This method can cover the vast majority of improvement needs for regular prescription lenses.

[0096] For example, this method is applicable when the original included angle of the front surface is less than 170° or greater than 190°, and the absolute value of the difference between the original included angle of the front surface and 180° is less than a predetermined threshold, i.e., the original included angle of the front surface is not an extreme angle. The predetermined threshold can be a relatively small value, such as 20°.

[0097] Figures 4 and 5 illustrate the optimization of the lens front surface angle using three sub-arcs. The dashed lines in Figures 4 and 5 represent the optimized three sub-arcs. Figure 4 optimizes lens front surface angles greater than 180°, while Figure 5 optimizes angles less than 180°. Combining Figures 4 and 5, it can be seen that, with the same sub-arc width, to better optimize the lens front surface angle, the sag allocated to the three sub-arcs should decrease when the lens front surface angle is greater than 180°. Conversely, when the lens front surface angle is less than 180°, the sag allocated to the three sub-arcs should increase.

[0098] This disclosure also experiments with combined improvement schemes of the proposed improvement scheme and various different improvement methods, and evaluates the compatibility and advantages and disadvantages of the combined schemes. Improved schemes for combined use include:

[0099] a. The multi-arc optimization scheme proposed in this disclosure;

[0100] b. Surface modification: By performing surface hydrophilic treatment on the material, such as low-temperature plasma treatment or hydrophilic coating treatment, the hydrophilicity of the material surface is improved, that is, the water contact angle of the lens surface is reduced to below 45°.

[0101] c. Improved oxygen permeability: Replace materials and use raw materials with higher oxygen permeability to improve corneal oxygen supply during lens wear. The lens material used has an oxygen permeability coefficient ≥125Dk.

[0102] d. Edge improvement: By thinning the edge of the lens, the friction and impact between the lens edge and the eyelid and cornea are reduced. The edge thickness used is 0.03 to 0.12 mm.

[0103] e. Fitting improvements: By improving the fitting of the posterior surface of the lens, the movement of the lens is reduced, thereby reducing friction between the lens and the eyelid and cornea. The improvements used include setting the base curve of the lens to an aspherical surface with an e-value of 0.4 to 0.6, and / or adding a fitting arc with a radius of curvature smaller than the base curve between the optical area of ​​the posterior surface of the lens and the edge curve.

[0104] f. Lubrication assistance: Before or during the first few minutes of wearing contact lenses, apply commercially available lubricating eye drops with lubricating properties to the eye wearing the lenses in three separate applications.

[0105] The above-mentioned improvement schemes were combined, and the comfort of the lenses was evaluated according to the following scoring rules. The experimental results are as follows.

[0106] The experimental results show that the comfort scores of combination schemes 4-9 are all higher than those of single factors. However, the coordination difficulty, compatibility, cost, and benefits of each combination differ. Combining multiple optimization and improvement methods can maximize lens comfort, but using too many optimization and improvement methods will lead to diminishing marginal returns and increase additional costs and coordination difficulties. Combining multi-arc optimization with multiple low-cost and highly compatible methods (Scheme 10) is an excellent scheme with good comfort improvement, controllable cost, and relatively high cost-effectiveness.

[0107] Therefore, based on the optimized design scheme described above in conjunction with Figure 1, this disclosure can also incorporate the following improvements to achieve an excellent solution with good comfort improvement, controllable cost, and relatively high cost-effectiveness. The improvements include any one or more combinations of the following: surface hydrophilic treatment of the lens material; use of lens materials with higher oxygen permeability; and thinning of the lens edges.

[0108] When applying the optimized design scheme disclosed herein to actual lens production, the following two methods can be selected.

[0109] First type of method

[0110] After allocating the diameter (i.e., width) and elevation for each sub-arc segment, the coordinate parameters of each sub-arc segment can be obtained, including the coordinates of the starting end and the ending end. The coordinate parameters of each sub-arc segment are input into the CNC machining equipment in the form of a queue, and programmed according to the coaxial circular interpolation method, so that the CNC machining equipment can complete the lens machining task through coaxial circular interpolation.

[0111] In other words, the coordinate parameters of each sub-arc segment in the peripheral area of ​​the front surface of the lens can be obtained. Then, the start and end coordinates of each sub-arc segment are input into a CNC lathe or other similar CNC machining equipment in a queue, and programmed using coaxial circular interpolation. This allows for the production of the improved lens. In this process, there is no need to calculate the radius of curvature of each sub-arc segment; any equipment supporting circular interpolation, even if its technology is two to three generations behind the latest technology, can successfully complete the machining task.

[0112] Second type of method

[0113] The optimized lens path diagram can be drawn and then submitted to CNC machining equipment for lens processing. In other words, a model can be adopted where the path diagram is drawn using drafting software and then imported into the CNC machining equipment for processing. This requires calculating the radius of curvature of each sub-arc segment for drafting. This optimization scheme avoids complex geometric or algebraic calculations, significantly reducing the difficulty of drafting tasks and substantially improving design and manufacturing efficiency.

[0114] Based on the above-mentioned optimized design method, this disclosure also proposes a rigid corneal contact lens.

[0115] Rigid contact lenses can be considered as lenses produced according to the optimized design method described above.

[0116] Rigid contact lenses consist of the lens body.

[0117] The target arc segment located on the front surface of the lens body is divided into a first number of sub-arc segments.

[0118] The target arc segment is at least one of two adjacent arc segments that participate in forming the original included angle on the front surface of the lens.

[0119] The original included angle of the front surface of the lens is the included angle of the front surface that needs to be optimized (i.e. before optimization).

[0120] The new included angle of the front surface of the lens formed after splitting (i.e., the optimized included angle) is closer to 180° than the original included angle of the front surface of the lens. The width of any sub-arc segment is greater than or equal to the first threshold, and the included angle between any two adjacent sub-arc segments is between 170° and 190°.

[0121] For more details regarding rigid gas permeable contact lenses, please refer to the relevant descriptions above.

[0122] In some embodiments, the original included angle of the front surface of the lens is the angle between the end of the optical region of the front surface of the lens and the beginning of the peripheral region of the front surface of the lens, and the target arc segment is the arc segment corresponding to the peripheral region of the front surface of the lens. The new included angle of the front surface of the lens may refer to the angle between the end of the optical region of the front surface of the lens and the beginning of the first sub-arc segment.

[0123] In some specific implementations, different sub-arc segments have the same width but different sags.

[0124] In some further embodiments, the first number is 3 to 12. If the original included angle of the front surface of the lens is greater than 180°, the sags of the first number of sub-arc segments are arranged in a decreasing arithmetic sequence from the inside to the outside. If the original included angle of the front surface of the lens is less than 180°, the sags of the first number of sub-arc segments are arranged in an increasing arithmetic sequence from the inside to the outside. The difference d of the arithmetic sequence satisfies the following condition. Where N equals the first quantity. For example, the first quantity is positively correlated with the absolute value of the difference between the original angle of the lens front surface and 180°.

[0125] In some further embodiments, the original included angle of the lens's front surface is between 170° and 190°, and the first number is 2. If the original included angle of the lens's front surface is greater than 180°, the proportion of the sag of the sub-arc segment relative to the center of the lens is 61.8%, and the proportion of the sag of the sub-arc segment relative to the edge of the lens is 38.2%. If the original included angle of the lens's front surface is less than 180°, the proportion of the sag of the sub-arc segment relative to the center of the lens is 38.2%, and the proportion of the sag of the sub-arc segment relative to the edge of the lens is 61.8%.

[0126] In some further embodiments, the original included angle of the front surface is less than 170° or greater than 190°, and the absolute value of the difference between the original included angle of the front surface and 180° is less than a predetermined threshold, the first number being 3. If the original included angle of the front surface is greater than 180°, the sag percentage of the sub-arc segment closest to the lens center is 42% to 52%, the sag percentage of the middle sub-arc segment is 30% to 36%, and the sag percentage of the sub-arc segment closest to the lens edge is 18% to 22%. If the original included angle of the front surface is less than 180°, the sag percentage of the sub-arc segment closest to the lens center is 18% to 23%, the sag percentage of the middle sub-arc segment is 31% to 36%, and the sag percentage of the sub-arc segment closest to the lens edge is 41% to 51%.

[0127] In some embodiments, the width and sag of each sub-arc segment are determined based on the above formulas (3) and (4). For the specific determination principle, please refer to the relevant description above.

[0128] The optimized design method of rigid gas permeable contact lenses according to this disclosure and the rigid gas permeable contact lenses have been described in detail above with reference to the accompanying drawings.

[0129] This disclosure can effectively improve the comfort of rigid contact lenses, and it does not conflict with other methods for improving the comfort of contact lenses, such as design adjustments, material modifications, and auxiliary drugs, and can be used in conjunction with them.

[0130] In addition, this disclosure provides a complete set of simple and easy-to-implement optimization solutions, which are accessible from logical calculation to production and processing. No complex hardware or software is required to complete the calculations. It does not require highly specialized manufacturing personnel, and ordinary people can easily understand and accept it. It also does not require powerful processing equipment for processing.

[0131] Overall, this disclosure is an improvement solution that is highly compatible, simple, effective, and inexpensive.

[0132] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An optimized design method for rigid gas permeable contact lenses, comprising: Obtain the original included angle of the front surface of the lens, which is used to characterize the included angle between two adjacent arc segments on the front surface of the lens, determined based on the lens prescription parameters; Determine whether the original included angle of the front surface of the lens needs to be optimized; If the original included angle of the front surface of the lens needs to be optimized, at least one target arc segment among the two adjacent arc segments that participate in forming the original included angle of the front surface of the lens is divided into a first number of sub-arc segments. The goal is to make the new included angle of the front surface of the lens closer to 180° than the original included angle of the front surface of the lens, the width of any sub-arc segment is greater than or equal to a first threshold, and the included angle between any two adjacent sub-arc segments is between 170° and 190°. The width and sag of the target arc segment are then assigned to the first number of sub-arc segments.

2. The method according to claim 1, wherein, The original included angle of the front surface of the lens is the angle between the end of the optical region of the front surface of the lens and the beginning of the peripheral region of the front surface of the lens. Dividing at least one target arc segment from two adjacent arc segments that participate in forming the original included angle of the front surface of the lens into a first number of sub-arc segments includes: dividing the peripheral area of ​​the front surface of the lens into a first number of sub-regions, each sub-region corresponding to a sub-arc segment.

3. The method according to claim 2, wherein, The first number is 3 to 12, and different sub-arc segments have the same width. If the original included angle of the front surface of the lens is greater than 180°, then the sagitta of the first number of sub-arc segments are arranged in an arithmetic sequence that decreases from the inside to the outside. If the original included angle of the front surface of the lens is less than 180°, then the sagitta of the first number of sub-arc segments are arranged in an arithmetic sequence that increases from the inside to the outside. The difference d of an arithmetic sequence satisfies, Where N is equal to the first quantity.

4. The method according to claim 3, wherein, The first quantity is positively correlated with the absolute value of the difference between the original angle of the front surface of the lens and 180°.

5. The method according to claim 2, wherein, The original included angle of the front surface of the lens is between 170° and 190°. The first quantity is 2, and different sub-arc segments have the same width. If the original included angle of the front surface of the lens is greater than 180°, then the proportion of the sagitta of the sub-arc segment closer to the center of the lens is 61.8%, and the proportion of the sagitta of the sub-arc segment closer to the edge of the lens is 38.2%. If the original included angle of the front surface of the lens is less than 180°, the proportion of the sag of the sub-arc segment relatively close to the center of the lens is 38.2%, and the proportion of the sag of the sub-arc segment relatively close to the edge of the lens is 61.8%.

6. The method according to claim 2, wherein, The original included angle of the front surface is less than 170° or greater than 190°, and the absolute value of the difference between the original included angle of the front surface and 180° is less than a predetermined threshold. The first quantity is 3, and different sub-arc segments have the same width. If the original included angle of the front surface is greater than 180°, then the sagittal proportion of the sub-arc segment closest to the lens center is 42%–52%, the sagittal proportion of the middle sub-arc segment is 30%–36%, and the sagittal proportion of the sub-arc segment closest to the lens edge is 18%–22%. If the original included angle of the front surface is less than 180°, the sag percentage of the sub-arc segment closest to the center of the lens is 18% to 23%, the sag percentage of the middle sub-arc segment is 31% to 36%, and the sag percentage of the sub-arc segment closest to the edge of the lens is 41% to 51%.

7. The method according to claim 1, wherein, Assigning the width and elevation of the target arc segment to the first number of sub-arc segments includes: determining the width and elevation of each sub-arc segment based on the following formula. Where r(n) is the radius of curvature of the nth sub-arc segment, S n Let d be the sag of the nth sub-arc segment. n-1 Let d be the inner diameter of the nth sub-arc segment. n Let A(n) be the outer diameter of the nth sub-arc segment, and let A(n) be the angle between the nth and (n+1)th sub-arc segments. n+1 Let be the radius of curvature of the (n+1)th sub-arc segment.

8. The method according to any one of claims 1 to 7, further comprising: Obtain the coordinate parameters of each sub-arc segment, the coordinate parameters including the starting end coordinates and the ending end coordinates; The coordinate parameters of each sub-arc segment are input into the CNC machining equipment in the form of a queue, and programmed according to the coaxial circular interpolation method so that the CNC machining equipment can complete the lens machining task through coaxial circular interpolation.

9. The method according to any one of claims 1 to 7, further comprising: Draw the path diagram of the optimized lens design, and then submit the path diagram to CNC machining equipment for lens processing.

10. The method according to claim 1, further comprising: The lens material undergoes a surface hydrophilic treatment; and / or Use lens materials with higher oxygen permeability; And / or The edges of the lens are thinned.

11. A rigid gas permeable contact lens, comprising a lens body, The target arc segment located on the front surface of the lens body is divided into a first number of sub-arc segments. The target arc segment is at least one of two adjacent arc segments that participate in forming the original included angle on the front surface of the lens. The original included angle of the front surface of the lens is the included angle of the front surface before optimization. The new included angle on the front surface of the lens is closer to 180° than the original included angle on the front surface of the lens. The width of any sub-arc segment is greater than or equal to the first threshold, and the included angle between any two adjacent sub-arc segments is between 170° and 190°.

12. The rigid gas permeable contact lens according to claim 11, wherein, The original included angle of the front surface of the lens is the included angle between the end of the optical region of the front surface of the lens and the beginning of the peripheral region of the front surface of the lens, and the target arc segment is the arc segment corresponding to the peripheral region of the front surface of the lens.

13. The rigid gas permeable contact lens according to claim 12, wherein, Different sub-arcs have the same width but different sags.

14. The rigid gas permeable contact lens according to claim 13, wherein, The first quantity is 3 to 12. If the original included angle of the front surface of the lens is greater than 180°, then the sagitta of the first number of sub-arc segments are arranged in an arithmetic sequence that decreases from the inside to the outside. If the original included angle of the front surface of the lens is less than 180°, then the sagitta of the first number of sub-arc segments are arranged in an arithmetic sequence that increases from the inside to the outside. The difference d of an arithmetic sequence satisfies, Where N is equal to the first quantity.

15. The rigid gas permeable contact lens according to claim 14, wherein, The first quantity is positively correlated with the absolute value of the difference between the original angle of the front surface of the lens and 180°.

16. The rigid gas permeable contact lens according to claim 13, wherein, The original included angle of the front surface of the lens is between 170° and 190°. The first quantity is 2. If the original included angle of the front surface of the lens is greater than 180°, then the proportion of the sagitta of the sub-arc segment closer to the center of the lens is 61.8%, and the proportion of the sagitta of the sub-arc segment closer to the edge of the lens is 38.2%. If the original included angle of the front surface of the lens is less than 180°, the proportion of the sag of the sub-arc segment relatively close to the center of the lens is 38.2%, and the proportion of the sag of the sub-arc segment relatively close to the edge of the lens is 61.8%.

17. The rigid gas permeable contact lens according to claim 13, wherein, The original included angle of the front surface is less than 170° or greater than 190°, and the absolute value of the difference between the original included angle of the front surface and 180° is less than a predetermined threshold. The first quantity is 3. If the original included angle of the front surface is greater than 180°, then the sagittal proportion of the sub-arc segment closest to the lens center is 42%–52%, the sagittal proportion of the middle sub-arc segment is 30%–36%, and the sagittal proportion of the sub-arc segment closest to the lens edge is 18%–22%. If the original included angle of the front surface is less than 180°, the sag percentage of the sub-arc segment closest to the center of the lens is 18% to 23%, the sag percentage of the middle sub-arc segment is 31% to 36%, and the sag percentage of the sub-arc segment closest to the edge of the lens is 41% to 51%.

18. The rigid gas permeable contact lens according to claim 11, wherein, The first threshold is 0.2 mm.

19. The rigid gas permeable contact lens according to claim 11, wherein, The included angle between any two adjacent sub-arc segments is between 176° and 184°.

20. The rigid gas permeable contact lens according to claim 11, wherein, The width and sag of each sub-arc segment are determined based on the following formula: Where r(n) is the radius of curvature of the nth sub-arc segment, S n Let d be the sag of the nth sub-arc segment. n-1 Let d be the inner diameter of the nth sub-arc segment. n Let A(n) be the outer diameter of the nth sub-arc segment, and let A(n) be the angle between the nth and (n+1)th sub-arc segments. n+1 Let be the radius of curvature of the (n+1)th sub-arc segment.

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