CN112255823B

CN112255823B - Contact lens

Info

Publication number: CN112255823B
Application number: CN202011262244.9A
Authority: CN
Inventors: W·E·梅耶斯; J·A·莱格顿; J·P·马什
Original assignee: Innovega Inc
Current assignee: Innovega Inc
Priority date: 2016-03-11
Filing date: 2016-03-11
Publication date: 2022-09-27
Anticipated expiration: 2036-03-11
Also published as: EP3427104A1; WO2017155552A1; CN109154724A; CN109154724B; JP2019515357A; CN112255823A; JP6993361B2; EP3427104A4

Abstract

A contact lens configured to limit the water transmission rate of at least one zone of the lens while maintaining at least a minimum oxygen transmission rate. The maximum water transmission rate and the minimum oxygen permeability are achieved by a predetermined lens thickness of a single lens material or by using layers of more than two materials.

Description

Contact lens

This application is a divisional application filed on 2016, 11/3, under the name of 201680085533.1, under the name of "contact lens".

Cross Reference to Related Applications

This application claims priority to U.S. provisional patent application No.62/083,198, filed on 11/22/2014, which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to the general field of optical lenses, and more particularly, to contact lenses configured to limit the water transmission rate (water transmission) of at least one area of the lens while maintaining at least a minimum oxygen transmission rate (oxygen transmission). The maximum water transmission rate and minimum oxygen permeability (oxygen permeability) values are achieved by a predetermined lens thickness of a single lens material or by using layers of two or more materials.

Background

The health of the eyes of consumers wearing contact lenses (contact lenses) greatly depends on the amount of oxygen transmitted through the lenses (lenses). The materials from which the lenses are made are typically selected for their oxygen permeability and much research has been conducted to determine the minimum amount of oxygen needed to maintain a healthy cornea.

Permeability or oxygen permeability more relevant to this discussion is mathematically explained using a coefficient Dk, where D is diffusivity (cm) ² Sec) is a measure of how fast oxygen moves through the material, and k isSolubility (ml O) ₂ Per ml material x mm Hg) is a measure of how much oxygen is contained in the material. The coefficient of oxygen transmission rate (Dk/t or Dk/L) is obtained by dividing the oxygen permeability of the material by the thickness of the material in centimeters.

The best penetration now provided for commercially available lens products is between Dk 80 and 150 x 10 ^-11 (cm ² /sec)(mL O ₂ ) /(mL. times.mm Hg) (Barrers). The material of these lenses is typically silicone acrylates or copolymers of silicone acrylates with hydrophilic monomers, thereby producing silicone hydrogels. The former are typically hard lenses and the latter are soft lenses. These lenses must be provided in a thin design to support corneal health, which can lead to problems of durability, handling, and dehydration in the case of hydrogels.

Dehydration, loss of water from the interior of the lens results in a change in the geometry (geometry) of the lens where the diameter, thickness and radius of curvature of the lens are reduced, a change in the optical power of the lens, and the lens exhibits poor wetting on the lens surface. Lens shrinkage can lead to shrinkage (tigening) of the lens on the eye, as indicated by a reduction in eye movement (eye movement), while poor wetting results in discomfort when the eyelids pass the lens while blinking. In general, the dewatering effect is solved by: the lens is given a posterior radius of curvature (porsterradius) that is longer than the curvature of the underlying cornea. In these cases, the lens shrinkage is only used to bring the lens into the correct relationship with the eye while maintaining lens movement. To prevent discomfort, the lens surface is treated in an attempt to reduce the wetting angle and thereby maintain the tear film on the front surface of the lens, or the lens is pre-loaded with a lubricious substance that seeps out onto the surface to maintain comfort during wear.

The above description is generally relevant for all lenses that are commercially available today, with one important exception. The exception is a lens made of silicone rubber (cross-linked polydimethylsiloxane, PDMS). PDMS is attractive for contact lens applications because, first, its permeability to oxygen is very high, more than twice that of the highest comparable materials; second, PDMS is soft and mechanically similar to human tissue; third, PDMS has a long history of safe use as a biomaterial in implants and wound dressings; fourth, PDMS is easily shaped into the final lens with highly transferred design features; and finally, PDMS is not a hydrogel and thus is not subject to bacterial invasion.

Unfortunately, PDMS (first appearing in contact lenses by nearly 50 years) has not been successful in the general contact lens market. One cause is often described as the problem of "sticking", which is also described as "lens adherence". Movement of the lens is generally not observed within as little as 15 minutes after application. In fact, early experience involved the actual adherence of the lens to the cornea, resulting in the loss of small plaques of epithelium upon removal of the lens. Although painful, such phenomena do not threaten vision because the cornea repairs itself rather rapidly; even so, any damage to the corneal surface creates an opportunity for infection.

PDMS lenses lost position in the general contact lens market, except for refractive correction of pediatric aphakia. This condition in untreated infants leads to blindness of the eye which, without exception, lacks the inner lens. The refractive treatment with PDMS contact lenses is unique to pediatric aphakic defects due to the requirements for extreme optical power in contact lenses requiring a thickness profile with a high central thickness. Adhesion problems are difficult to observe in such applications. Thick lenses are known to promote lens movement due to forceful contact with the eyelid during blinking. In addition, due to high oxygen permeability, pediatric aphakic lenses have regulatory approval for continuous wear for up to 30 days; thus, there is no need to remove the lens frequently, thereby reducing the likelihood of epithelial detachment.

Following the inference of pediatric success using lenses with thick centers and using methods that improve wafer surface wetting (typically plasma processing) led to early attempts to address the lens sticking problem. The development of a modified lens geometry design combining a lens that is loosely eye-related with a plasma treated lens has not been successful. Because the lens contains little water (typically less than 0.2%), lens dehydration does not appear to be a possible cause of lens sticking.

PDMS contact lenses have high oxygen solubility and large oxygen diffusivity (internal flux) resulting from the extreme mobility of silicon atoms in the polymer and these properties lead to very high oxygen permeability (Dk). The permeability is actually the product of these two properties. The diffusivity of the permeate, as discussed above for oxygen, is a property. The second property is the solubility of the permeate in the material permeated through. Materials with high values for both properties of a particular permeate often have a high permeability to that permeate. Because PDMS has a very low solubility for water, it is generally assumed that water can be transported through the material at a low rate. Following this assumption, one would conclude that shrinkage due to dehydration is not possible and that water transport due to osmosis is minimal. Strategies to minimize water transport have not been recognized or reported as a possible approach to solving the "sticking" problem.

It is recognized that the assumption of low water transmission rate of contact lens designer's PDMS is wrong and that water transmission rate itself is the main cause of lens sticking and is also the basis of the present invention. Although liquid water is barely detectable within the PDMS lens, water vapor molecules are able to freely pass through the material. In fact, although the permeability to oxygen through the material is impressive, the permeability to water vapor is more than 50 times greater. Water permeability of this order of magnitude is capable of delivering the entire amount of tear water from under the lens in a matter of minutes. The tear film behind the lens and the water associated with the epithelial mucin layer (epithelial mucin layer) can make the surfaces of the lens and cornea hydrophobic, thereby increasing attraction of each other (attraction). Such attraction of the hydrophobic surface will inevitably result in sticking and non-moving. These effects would be unlikely to be mitigated by surface treatments or loosely fitting lens design strategies. Some improvement is observed by wearers such as infants exposed to the lens: including greater than the standard duration of closed-eye wear.

It was originally thought that a solution to adhesion would be to find other materials with very high oxygen transmission rates but not rapid water transmission rates. Of course, such materials would require mechanical properties suitable for contact lenses, be relatively inexpensive and can be manufactured by low cost methods such as automated cast molding, and require little stock keeping units (SKUs's) to cover the vast majority of patients. The new material will have to be non-toxic and satisfactorily biocompatible, while being easy to set (fit), comfortable to wear and optically transparent. Research into such materials has been conducted for nearly 50 years and materials have been proposed that meet all of these requirements. Lenses made of gas permeable rigid materials have been the closest, but are less comfortable to wear, difficult to set (fit), expensive to manufacture and require more stock keeping units.

Holden and Mertz establish standards for maintaining a standard corneal physiologic minimum oxygen transmission rate for wearing contact lenses with open eyes (daily wear) and lenses under standard overnight sleep times (extended wear or continuous wear).

Holden and Mertz investigated critical oxygen levels to avoid corneal edema and limited them in terms of oxygen transmission rate and percent equivalent oxygen. The relationship between corneal edema and hydrogel lens oxygen transmission rate was examined for both daily and extended contact lens wear by measuring the corneal swelling response induced by various contact lenses over a 36 hour wear period. This relationship results in a mean edema level that is allowed to occur in the normal young population under daily and extended wear, which is expected to be within ± 1.0%. The critical lens oxygen transmission rate required to avoid edema for daily and prolonged contact lens wear is obtained from the resulting curves. Holden and Mertz found that the oxygen transmission rate (Dk/t) is at least 24.1 + -2.7X 10 under daily wear conditions ^-9 (cm ³ O ₂ )/(cm ² S mmHg) or Barrers/cm, with an equivalent oxygen percentage (EOF) of 9.9%, did not cause corneal edema.

Disclosure of Invention

The present invention solves the problem by an alternative approach; lenses were created that at least met the minimum criteria for oxygen transmission rate for Holden Mertz while exhibiting water transmission rates no greater than those of successfully commercialized contact lenses. Means for reducing water transport rates while maintaining a minimum level of oxygen transport rates are disclosed. A first embodiment of the invention is a lens having a predetermined thickness to reduce the water transmission rate of the ultra-high permeability lens material to a maximum acceptable level while maintaining the oxygen transmission rate to a minimum acceptable level. A second embodiment of the invention is a lens comprising at least two materials, wherein the combined materials are configured as a single device to reduce the water transmission rate of the composite lens to a maximum acceptable level while maintaining the oxygen transmission rate to at least a minimum acceptable level.

Historically, the parallel-looking approach has been considered in lenses known as hybrid or composite lenses, however this approach (e.g. in Saturn Lens, Softperm Lens, synergy lenses brands) does not attempt to work the contained materials together by fusing (merging) their properties by using widely different materials at different locations to present separate functions (side by side), center of eye and periphery of eye). The prior inventions provide materials that in turn exhibit their aggregate properties to achieve the desired properties at the same location of the lens and thus at the same location of the eye. The prior invention makes a "sandwich" of dissimilar materials or a layered construction of materials parallel and perpendicular to the axis of the lens, rather than coaxial with the axis of the lens, as in the above-described composite or hybrid lenses.

The prior art also discloses lenses having an anterior hard layer and a posterior soft layer for the reason of providing lens comfort while presenting a hard optical lens when in contact with the eye. Such laminate lenses do not address the issue of balancing the maximum acceptable water transmission rate while maintaining at least a minimum oxygen transmission rate.

Additional techniques teach lenses having an air cavity, and the cavity is filled with a fluid and gel material, which do not address the problem of limiting the lens to a maximum water transmission rate while maintaining a minimum oxygen transmission rate. The prior art also discloses the inclusion of components and elements in the lens which do not address the problem of balancing the maximum acceptable water transmission rate while maintaining at least a minimum oxygen transmission rate.

It is an object of the present invention to provide a contact lens having a minimum oxygen transmission rate to maintain standard corneal physiology for wearing the contact lens.

It is another object of the invention to provide contact lenses having water transmission rates no greater than those of other successfully commercialized contact lenses.

It is a further object of the present invention to provide a composite soft or hard contact lens having a water transmission rate below a maximum acceptable level while having an oxygen transmission rate at least a minimum acceptable level.

Terms and phrases used in this document, and variations thereof, unless expressly stated otherwise, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term "comprising" should be understood to mean "including but not limited to" and the like; the term "example" is used to provide illustrative examples of the items in question, rather than an exhaustive or limiting list thereof; the terms "a" or "an" should be understood to mean "at least one," "one or more," and the like; and adjectives such as "conventional," "customary," "conventional," "standard," "known," and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but rather should be read to encompass conventional, customary, conventional, or standard technologies that may be available or known at any time, whether now or in the future. Likewise, where the document refers to technology that is obvious or known to one of ordinary skill in the art, that technology encompasses technology that is obvious or known to one of ordinary skill in the art at any time now or in the future.

The presence of broad words and phrases such as "one or more," "at least," "but not limited to," and the like, or other similar phrases in some instances will not be understood to mean as follows: narrower cases may be intended or required in instances where the broader phrase may be lacking. In addition, the various embodiments set forth herein are illustrated in exemplary block diagrams, flowcharts, and other pictorial forms. As will be apparent to those skilled in the art upon reading this document, the illustrated embodiments and their various alternatives can be implemented without being limited to the illustrated examples. For example, block diagrams and their accompanying description should not be read to imply a particular architecture or configuration.

As used herein, a contact lens is made from one or more layers of films, including composite films. Composite membranes are membranes made from multiple membranes, including multilayer membranes. In some embodiments, although not necessarily all embodiments, the contact lens is made only of a composite film, in which case the terms may be used interchangeably.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. Additional features of the invention will be described hereinafter and will form the subject of the claims appended hereto. The features set forth herein, as well as other features, aspects, and advantages of the present invention, will become better understood with reference to the following description and appended claims.

Drawings

The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the invention be limited not by the claims and the equivalents thereof.

Fig. 1 is a cross-sectional view of a contact lens having a first thickness and a second, greater thickness in accordance with selected embodiments of the present invention.

Fig. 2 is a cross-sectional view of a contact lens having two layers with varying permeability to oxygen and to water vapor in accordance with selected embodiments of the invention.

Fig. 3 is a cross-sectional view of a contact lens having multiple layers with varying permeability to oxygen and to water vapor in accordance with selected embodiments of the invention.

Fig. 4 is a cross-sectional view of a contact lens having an outer lens material layer and an inner material layer in accordance with selected embodiments of the present invention.

Fig. 5 is a cross-sectional view of a contact lens having an outer lens material layer, an inner material layer, and an adhesive layer between these layers, in accordance with selected embodiments of the present invention.

Fig. 6 is a cross-sectional view of a contact lens having an outer lens material layer and an inner lens material layer displaced in the area of the contact lens according to selected embodiments of the present invention.

FIG. 7 is a graph of the permeability of a composite to oxygen and water as a function of the fraction of those permeabilities initially represented by the full thickness of only one of the materials, the second material having a different permeability to oxygen and water vapor, before including a layer of the second material and changing to those initial permeabilities by exchanging a partial thickness of the layer of the initial material for an equivalent partial thickness layer of the second material.

FIG. 8 is a graph showing the ratio of oxygen permeability (P) therein _O1 /P _O2 ) Graph of the first scheme held constant.

FIG. 9 is a graph showing the oxygen permeability ratio (P) thereof _O1 /P _O2 ) Graph of the second scheme held constant.

Detailed Description

Many aspects of the invention can be better understood with reference to the following drawings that are illustrated below. The components in the drawings are not necessarily to scale. Rather, emphasis is placed upon clearly illustrating the components of the present invention. Moreover, like reference numerals designate corresponding parts throughout the several views of the drawings.

The first embodiment of the present invention comprises a single lens material having ultra-high permeability to oxygen and water vapor. The thickness profile of the lens is selected to reduce the water transmission rate to a maximum level or below while maintaining the oxygen transmission rate at a minimum level or above. Fornasiero and colleagues (2005) measured steady state diffusion of water through commercially successful hydrogel and silicone hydrogel lens materials, while Rofojo (1980) measured water transport through silicone rubber lens materials. While the metrics of the two studies were reported to be different, this conversion can turn the water permeability into a common metric (common metric).

In parallel, the lens thickness profiles of two of the commercially successful lenses are known. The resulting water transmission rate was calculated as water permeability divided by thickness. Notably, water permeability varies with the humidity surrounding the material at which it is measured. Further, the permeability may change as the hydrogel material dehydrates and thins. Even so, for the purposes of the present invention, an average value of the range of ambient humidity may be used.

Water permeability can be reported as equal to μ g/μm cm ² s-1 or cm/. mu.m and can be converted into cm ³ /μgH ₂ O and mmHG/Atm, which in turn can be converted to Barrers. Such a conversion allows the measured values of water permeability of conventional hydrogels and silicone hydrogels to be compared to the reported values of water permeability of silicone rubber materials. The following table shows reported values for comparison:

TABLE 1

Material	Flow rate	% humidity	Thickness	Water permeability Barrers
					Polymacon	4.7	50	145	11110
Balafilcon	8.05	50	144	18964
					Elastifilcon	NA	NA	NA	40000

*10 ^-6 g·cm ^-2 ·s ^-1

Steady state

***10 ^-11 [cm ³ ·cm]/[cm ² ·s·mmHg]

The historical reports of lens thickness for Polymacon include commercial lenses ranging from a central thickness value of 0.04 to 0.18 mm. Most lenses have central thickness values between 0.08 and 0.12mm or an average value of 0.10 mm. Lenses made from polymacon have shown more than 50 years of sustained use (restated use) without reports of lens adhesion. The long-term commercial success of Polymacon lenses studied and the reported absence of lens adhesion or "blocking" indicate that the water vapor transmission rate is sufficiently low to prevent the depletion of the tear layer behind the lens. Notably, polymacon constitutes a small percentage of the new mount because it also has a low oxygen permeability and falls below the Holden Mertz standard for oxygen transfer for open eye wear.

The present invention provides one embodiment for using a predetermined lens thickness as a criterion or criteria for reducing the water transmission rate to approximately the level exhibited by a polymacon lens while maintaining the oxygen transmission rate at or above the Holden Mertz criterion for open eye wear. The Holden Mertz value set for minimum oxygen transmission rate (Dk/t) of the lenses of the invention is 24.1 + -2.7X 10 ^-9 (cm ³ O ₂ )/(cm ² s.mmHg). By way of example, one of the polydimethylsiloxanes has been reportedVariant Dk 340 × 10 ^-11 (cm ² /sec)(mL O ₂ ) /(mL. times. mm Hg). Other variations of the same material may have higher or lower Dk measurements.

By Dk 340 x 10 ^-11 (cm ² /sec)(mL O ₂ ) The central thickness of a lens made of material of/(mL × mm Hg) can be as high as 0.141cm to maintain Dk/t at 24.1 × 10 ^-9 (cm×ml O ₂ ) /(sec. times.ml. times.mmHg). While this is an order of magnitude larger than commercial lenses, oxygen transmission rates are expected to meet open eye (daily wear) requirements. Such thickness will also reduce the water transmission rate of the same lenses to a level well below that shown by commercially successful polymacon and silicone hydrogel lenses.

Since lenses with a thickness of 1.41mm are excessive and unprecedented, the present invention aims to minimize the thickness to achieve a water transmission rate substantially equivalent to polymacon. The harmonic thickness of the polymacon lens is selected to be 0.08mm, resulting in the maximum water transmission rate limiting the invention. By way of example, the water transmission rate of polymacon at 50% humidity, converted to permeability in Barrers, is 11,110. Using the harmonic thickness as a 0.008cm lens, the water transmission rate (B/t) of the lens example was found to be 13,887.5. Continuing by way of example, the reported permeability values for the polydimethylsiloxane variant were found to be 40,000 Barrers. To achieve one embodiment of the lenses of the invention, a lens thickness (t) of 13887.5, calculated as 0.029cm, is achieved with a material having a water permeability of 40,000 in Barrers, which is greater than 3 times the thickness of a typical lens (average lens) made from a hydrogel and a silicone hydrogel material. In a particular embodiment, the contact lens has an average thickness of greater than 0.4 mm. In another embodiment, the contact lens has an average thickness of greater than 0.3 mm. In yet another embodiment, the contact lens has an average thickness of greater than 0.2 mm.

Particular embodiments of the invention provide lenses having a lens area of a predetermined thickness throughout the bulk of the corneal surface, regardless of the lens power. This is different from the lenses made of polydimethylsiloxane, which has a height only at the geometric center of the lensThickness and thinning rapidly due to the convex curvature of the anterior surface being smaller in radius than the concave curvature of the posterior surface of the optic and for the purpose of creating high power diopters (high power diopters) to correct aphakia defects. By way of example, lenses of the invention that have no power and have parallel faces or have the usual power for refractive index correction include lenses for making the water transmission rate no greater than B/t-13887.5 Barrers/cm; while resulting in an oxygen transmission Dk/t of greater than or equal to 24.1 + -2.7X 10 ^-9 (cm×ml O ₂ ) /(sec. times.ml. times.mmHg) thickness.

Those skilled in the art of contact lens design and manufacture will recognize that the most preferred solution to the dilemma of high water transmission rates coupled with high oxygen permeability would be to inherently possess materials that are permeable to these components such that both oxygen and water transport are physiologically required. Of course, one skilled in the art will recognize that such materials will also have to meet all the requirements necessary for an acceptable contact lens (biocompatibility, good wettability, suitable mechanical properties, non-toxicity, durability, and cost-effectiveness). Work on this goal has continued to date, however, even after 50 years of research, such products have not been reported.

In view of this fact, the above-presented embodiments provide a solution to this dilemma, while alternative embodiments provide different approaches: methods of employing different materials in a composite construction that each meet some requirements for lens acceptability, where the individual limitations of the combined materials are mitigated by the degree and or location of placement of the components within the final product. For example, mechanical limitations can be mitigated by using a minimum thickness in the lens, and biocompatibility or post-lens tear film quantity can be mitigated by insulating such components within a "sandwich" of materials that perform better in those respects.

More specifically, an alternative embodiment of the invention is a lens comprised of at least two separate layers arranged in such a way that the more biocompatible layer can be the element in contact with the anterior and posterior tear film. Elements possessing less desirable mechanical properties or oxygen permeability would be arranged as thin layers. The relative thicknesses of the various layers within the sandwich structure will be applied in accordance with the oxygen and water permeability of the various materials. The relative thickness determining factor will be their combined permeability to oxygen and their combined permeability to water vapor while attempting to maintain maximum oxygen permeability and minimum water vapor permeability. It is important to note that it is not a mathematical addition of permeability; rather, they are properly combined with the recognition that the combined performance actually represents a permeability resistance that is contrary to the allowable amount of transmission. A suitable mathematical expression is:

equation 1

Wherein P is the permeability of the complex to a particular permeate and E _i Is the thickness of the i-th layer, P _i Permeability to the same permeate of the i-th layer and E _t Is the total thickness in mm of the composite. The permeability must be expressed in the same units, preferably by a similar method. Thus, new permeabilities can be derived for the composite for each of the permeates in question. Further, it is convenient for each permeate to represent its corrected permeability as a fraction of the original permeability of the material having the highest permeability to that permeate. This represents an acceptable compromise of the permeate by sandwiching it with other material layers.

In certain embodiments, it is desirable to maintain a constant thickness of the gripping layer in the lens. In an alternative embodiment, the thickness of the inner layer may vary within the sandwich structure. By way of example, the contact lens of the present invention may require oxygen delivery to be more important to the cornea, while hypoxia (oxygen depletion) may be less of an issue beyond the corneal boundary where some oxygen is supplied through the underlying vasculature (vasculature). Conversely, water loss from the lacrimal pool under the lens is likewise negatively affected by water loss through the periphery of the lens rather than the center. The peripheral area for water loss is naturally larger than the central area of the lens. If the peripheral region is provided with a thicker clamping layer that is resistant to water transport, the total loss of the lacrimal pool, regardless of the loss attendant to oxygen transport, will be substantially affected, while the curtailment in oxygen availability will be mitigated by the lesser need for oxygen and the availability of alternative sources below the periphery of the lens.

It is also possible that the manufacture of the sandwich structure requires the adhesion of the individual layers, and that an adhesive film may be required between the main layers. The permeability of these adhesive films is chosen such that in the very thin films required for adhesion, they will have little effect on the overall permeability of the composite. However, if they have a greater impact, they should also be included in the composite permeability calculations. In rare cases to obtain a good adhesion it may be necessary to insert a thin conforming layer(s) between the main layers, so that a sandwich structure is made of main and sub-layers, wherein all such layers are separated by an adhesive film. Again, the final composite permeability will be derived by the expression given above. In other cases, no adhesive may be required, such as when the major layers are inherently adhered to each other or the inner layers are simply encapsulated within the outermost layer which extends slightly beyond the inner layers and is bonded there by adhesive at the perimeter (perimeter), or indeed the expansion of a single encapsulating layer which is the outermost layer formed during the forming process.

The selection process of the composition and thickness of the layers of the sandwich structure is most conveniently performed using derivatives of the mathematical expressions given above. As an example, consider the permeation of oxygen and water through a sandwich structure consisting of two outer layers of one material and one inner layer of the other material. It is further contemplated that the two materials have different ratios of permeability to oxygen and water, such that in one material, the water permeability ratio is highly favorable for the transport of water rather than oxygen, and in the second material, the permeability of water is greatly reduced relative to the permeability of oxygen. The goal is to make a two-material composite sandwich structure in which the water transmission rate is greatly reduced relative to the oxygen transmission rate and the overall result is a reduction in the residual level of oxygen transmission, which remains within acceptable levels for the desired lens wear schedule, while the water transmission rate of the composite is reduced compared to layer 1 alone. From the original magnitude of oxygen permeability, one can select the fraction of the original oxygen permeability targeted and calculate the residual fraction of water permeability. These calculations are listed below:

equation 2

Equation 3

T is the total thickness of the composite; f is the fraction of the thickness of the composite occupied by the material with the highest oxygen permeability; p _OC Is the oxygen permeability of the composite; p _O1 Is the oxygen permeability of the first material; p is _O2 Is the oxygen permeability of the second material; p _WC Is the water permeability of the composite; p is _W1 Is the water vapor permeability of the first material; and P is _W2 Is the water vapor permeability of the second material.

Literature values for the permeability to water and oxygen using polydimethylsiloxane and amorphous teflon with a thickness of 1mm, P _O1 Oxygen permeability of polydimethylsiloxane; p _O2 Oxygen permeability as amorphous teflon; p is _W1 Is the water vapor permeability of polydimethylsiloxane; and P is _W2 Water vapor permeability of amorphous teflon. In view of these values, the composite can maintain greater than 80% of the oxygen permeability of pure PDMS while reducing the water permeability to slightly more than 10% of that of pure PDMS.

FIG. 7 is a graph of the change in permeability of the composite to oxygen and water. While the absolute values of the fractions indicated by the endpoints in the graph are controlled by the absolute values of the permeabilities of the two components, other very important features of these values are revealed in the graph. This feature is the asymmetry of the two functions (asymmetries). Although the oxygen permeability regresses relatively linearly from a high point when no second component is present to a low point when only the second component is present, the behavior of the water permeability function is quite different. When initially comprising even a very thin layer of the second component, the water permeability of the composite is drastically reduced compared to the water permeability of the first component. Such asymmetry provides an excellent increase in water permeability of the composite compared to the first material with little effect on oxygen permeability. A very thin layer of the second material is sufficient to greatly reduce the excessive water permeability of the first material without compromising the excellent oxygen permeability of the first material.

The aspect of permeability used in the composite that is the largest cause of this preferred asymmetry in the results is the ratio of the water permeability of the first material relative to the water permeability of the second material (P) _Wl /P _W2 ) Ratio of oxygen permeability of the first material to oxygen permeability of the second material (P) _O1 /P _O2 ) Contrast inconsistency (disparity). The greater the disparity, the greater the asymmetry. In this particular case, where it is desired to retain the oxygen permeability and at the same time preferably reduce the water permeability, the ratio of oxygen permeability (P) is chosen _O1 /P _O2 ) Kept small while the water permeability ratio (P) is small _Wl /P _W2 ) The substantially larger second material results in a successful relatively large reduction in water permeability with little reduction in oxygen permeability by including a very thin layer of the second material in the first material.

FIG. 8 shows a graph of the first scheme, in which the oxygen permeability ratio (P) _O1 /P _O2 ) Remains constant, but water permeability ratio (P) _Wl /P _W2 ) Larger than in fig. 7. FIG. 9 shows a graph of a second scheme, in which the oxygen permeability ratio (P) _O1 /P _O2 ) Remains constant, but water permeability ratio (P) _Wl /P _W2 ) Smaller than in fig. 7. In which the oxygen permeability ratio (P) _O1 /P _O2 ) In these two graphs, which remain constant, one sees the water permeability ratio (P) in two alternative cases _Wl /P _W2 ) Different (one less positive and one more positive). It is observed that the more positive the ratio, the greater the preferred asymmetry in the function.

In particular embodiments, the medium or second component or material within the first material has a water permeability of less than 10,000Barrers and an oxygen permeability of greater than 200 Barrers. Another embodiment provides that the area of the composite membrane of the contact lens, measured as more than 50 square millimeters, has a water transmission rate providing a maximum value below, for example, 13887.5Barrers/cm while providing a water transmission rate higher than, for example, 24.1X 10 ^-9 (cm×ml O ₂ ) /(sec × ml × mmHg) minimum value of oxygen transmission rate.

As discussed above, the permeability to a particular permeate is proportional to the permeability to the permeate by taking the first material (e.g., P) _O1 ) Permeability to a permeant (e.g., P) with (or exceeding) a second material _O2 ) Is calculated. In certain embodiments, the contact lens has a different ratio of permeability for the two permeants. As indicated above, the composition of the two different layered materials may be selected such that the second permeate ratio is greater than the first permeate ratio. For example, the contact lens may have a first permeate ratio to permeate oxygen that is less than a second permeate ratio to permeate water (or water vapor). In a particular embodiment, the composition of the layered material is selected such that the first permeate ratio is 5 or less and the second permeate ratio is 10 or more. In another embodiment, the first permeate ratio is 3 or less and the second permeate ratio is 20 or more. In yet another embodiment, the first permeate ratio is 2 or less and the second permeate ratio is 30 or more.

The difference between the permeability of the composite contact lens' permeant and the layered material can be expressed as a percentage difference relative to the layered material. In particular embodiments, the composition of the medium and the layer thickness of the medium are selected such that the composite contact lens has a permeability to the first permeate, e.g., oxygen, that is no less than 20% of the permeability to the first permeate of the host material, e.g., crosslinked polydimethylsiloxane. In another embodiment, the permeability of the composite membrane to the first permeate is not less than 50% of the permeability of the host material to the first permeate. In yet another embodiment, the permeability to the first permeate of the composite membrane is not less than 75% of the permeability to the first permeate of the host material. In yet another embodiment, the permeability to the first permeate of the composite membrane is not less than 90% of the permeability to the first permeate of the host material. In yet another embodiment, the permeability of the composite membrane to the first permeate is not less than 95% of the permeability of the host material to the first permeate.

The composite membrane of another embodiment has a permeability to a second permeate, such as water or water vapor, that is no greater than 95% of the permeability to the second permeate of the host material, such as crosslinked polydimethylsiloxane. In another embodiment, the permeability of the composite membrane to the second permeate is no greater than 90% of the permeability of the host material to the second permeate. In further embodiments, the permeability of the composite membrane to the second permeate is no greater than 75% of the permeability of the main material to the second permeate. In yet another embodiment, the permeability of the composite membrane to the second permeate is no greater than 50% of the permeability of the host material to the second permeate. In a further embodiment, the permeability of the composite membrane to the second permeate is no greater than 25% of the permeability of the main material to the second permeate. In a further embodiment, the permeability of the composite membrane to the second permeate is no greater than 10% of the permeability of the main material to the second permeate.

Referring now to FIG. 1, a contact lens 100 in accordance with selected embodiments of the present invention is depicted. For the purpose of reducing the water transmission rate of the finished lens to the limits of the invention, the contact lens 100 has a first thickness 101, bounded by a first front surface 102, that is close to the thickness of a conventional contact lens, and an additional lens thickness 103 of the same material. In a particular embodiment, the first lens thickness 101 is a film of a host material and the further lens thickness 103 is the same film of the host material, wherein the film of the host material is at least partially made of a polymer comprising cross-linked polydimethylsiloxane or an alternative material having a Dk equal to or greater than 200 Barrers.

As will be understood by those skilled in the art, particular embodiments of the present invention may have additional thicknesses 103 that are not limited to locations at the anterior surface, are not limited to symmetric configurations, are not limited to uniform thickness distributions, and are not limited to central locations relative to the geometric center of the contact lens 100. For example, additional thicknesses may be employed, symmetrically or asymmetrically, or a localized arrangement may be employed. In this manner, the lens can be customized to include multiple and various thickness profiles to provide the desired oxygen and water transmission rates of the finished contact lens 100. Further, the first thickness 101 and the additional lens thickness 103 may be one continuous element, or the encapsulated components each have two separate layers contacting the surface of the other.

Fig. 2 depicts a contact lens 200 in accordance with selected embodiments of the present invention. For the purpose of reducing the water transmission rate of the finished lens to the limits of the invention, the contact lens 200 has a first material film 201 bounded by a first material interface 202 and a second material film 203 bounded by a front surface 204. In a particular embodiment, the first material film 201 is a primary material film and the second material film 203 is a layered secondary material film, wherein at least one of the layered primary material film or the layered secondary material film is made at least in part from a polymer comprising cross-linked polydimethylsiloxane or an alternative material having a Dk equal to or greater than 200 Barrers.

As will be understood by those skilled in the art, particular embodiments of the present invention may have a secondary material film that is not limited to a location at the anterior surface, is not limited to a symmetrical configuration, is not limited to a uniform thickness distribution, and is not limited to a central location relative to the geometric center of the contact lens 200. For example, a secondary material film may be employed behind or in front of the primary material film. The sub-material films may be employed symmetrically or asymmetrically, or may be employed in a localized arrangement. In this manner, the lens may be customized to include multiple and multiple thickness profiles of the primary and secondary material films to provide the desired oxygen and water transmission rates of the finished contact lens 200. Further, the first material film 201 and the second material film 203 may be one continuous element, or the packaged components each have two separate layers contacting the surface of the other.

Fig. 3 depicts a cross-section of a portion of a contact lens 300 in accordance with selected embodiments of the present invention. Multilayer contact lens 300 has an anterior layer 301, a posterior layer 302, a first internal layer 303, a second internal layer 304, and a third internal layer 305. Contact lens 300 exhibits an associated water transmission rate in the direction of arrow 306, from the back of the environment to posterior layer 302 and toward the front of the environment to anterior layer 301.

With continued reference to fig. 3, contact lens 300 exhibits a relative oxygen transmission rate in the direction of arrow 307, from the front of the environment to anterior layer 301 and toward the back of the environment to posterior layer 302. As will be understood by those skilled in the art, particular embodiments of the invention may have layers that are not limited in number, are not limited to local locations within the lens 300 or apparent relative depths (apparent relative depths), are not limited to symmetrical configurations, are not limited to uniform thickness distributions, and are not limited to central locations relative to the geometric center of the contact lens 300. For example, fewer or additional layers or deeper or shallower arrangements of layers may be employed, or localized arrangements may be employed. In this manner, the lens may be customized to include multiple and various layers, and the thickness of the layers may be determined to provide a desired transmission rate of oxygen and water.

Fig. 4 depicts a cross-section of a layered contact lens 400 in accordance with selected embodiments of the present invention. The layered contact lens 400 has a first material 401 and a second material layer 402. The second material layer 402 of the contact lens 400 has a variable thickness profile and is placed in one region of the contact lens 400. In a particular embodiment, the first material 401 is a layered primary material film and the second material layer 402 is a layered secondary material film. The layered main material film is made at least in part from a polymer comprising a silicone acrylate. Optionally, the layered host material film is made at least in part from a polymer comprising cross-linked polydimethylsiloxane or an alternative material having a Dk equal to or greater than 200 Barrers. The layered sub-material film is made from a film having a water permeability of less than 10,000Barrers, such as a film comprising an amorphous or crystalline fluorocarbon resin. Optionally, the layered sub-material membrane is made of a polyurethane-containing membrane having a water permeability of less than 10,000 Barrers. In yet another alternative embodiment, the layered sub-material membrane is made at least of a silicone-containing membrane having a water permeability of at least less than 10,000 Barrers.

With continued reference to fig. 4, the second material 402 is thicker at its center and thinner at its peripheral edges. The contact lens 400 includes a posterior layer of a first material 401 posterior to a layer of a second material 402 and having a uniform thickness. Further, contact lens 400 includes an anterior layer of first material 401 that is thinner anterior to and at the center of second material 402 and thicker in the mid-peripheral portion (mid periphery) of the anterior layer. As will be understood by those skilled in the art, particular embodiments of the present invention provide layers that are not limited in number, are not limited in their location at apparent thicknesses within the contact lens 400, are not limited to symmetrical configurations, are not limited to uniform thickness distributions, and are not limited to a central location relative to the geometric center of the contact lens 400. For example, additional layers or deeper or shallower arrangements of layers may be employed, or localized arrangements may be employed. In this manner, the lens may be customized to include multiple and various layers, and the thickness of the layers may be determined to provide a desired transmission rate of oxygen and water.

Fig. 5 depicts a cross-section of a layered contact lens 500 in accordance with selected embodiments of the present invention. Layered contact lens 500 has a first material 501, a second material layer 502, and an adhesive layer 503. The second material layer 502 of the contact lens has a variable thickness profile and is placed in one area of the contact lens 500.

With continued reference to fig. 5, the second material 502 is thicker at its center and thinner at its peripheral edges. The contact lens 500 includes a posterior layer of a first material 501 posterior to a layer of a second material 502 and having a uniform thickness. Further, contact lens 500 includes an anterior layer of first material 501 that is thinner anterior to second material 502 and at its center and thicker in the mid-peripheral portion (mid periphery) of the anterior layer. The adhesive layer 503 surrounds the second material layer 502. In alternative embodiments, the adhesive 503 does not surround the second layer and may be applied to only a portion of the surface of the region of the layer.

As will be appreciated by those skilled in the art, particular embodiments of the present invention provide one or more adhesives having the same or different relative permeabilities and applied in a stacked manner or locally. Further, the layers are not limited in number, are not limited in their location at apparent thicknesses within the contact lens 500, are not limited to symmetrical configurations, are not limited to uniform thickness distributions, and are not limited to a central location relative to the geometric center of the contact lens 500. For example, additional layers or deeper or shallower arrangements of layers may be employed, or localized arrangements may be employed. In this manner, the lens may be customized to include multiple and various layers, and the thickness of the layers may be determined to provide a desired transmission rate of oxygen and water.

Fig. 6 depicts a cross-section of a layered contact lens 600 in accordance with selected embodiments of the present invention. Layered contact lens 600 has a first material 601, a second material layer 602, and a third material 603 around the second material 602. The second material 602 has a relatively uniform thickness distribution and is placed in the central region of the contact lens 600. Layer 602 may optionally have the same composition as layer 601. Third material 603 has a variable thickness profile and is placed in the mid-peripheral region (mid-peripheral region) of contact lens 600.

With continued reference to fig. 6, the thickness of the second material 602 is relatively uniform. Third material 603 is thicker at its center and thinner at its peripheral edges. Contact lens 600 includes a posterior layer of first material 601 that has a relatively uniform thickness and is posterior to second material layer 602 and third material 603. Further, contact lens 600 includes an anterior layer of first material 601 that is thinner at its center, thicker at its mid-peripheral portion (mid periphery), and anterior to second material 602 and third material 603.

As will be understood by those skilled in the art, particular embodiments of the present invention provide layers that are not limited in number, are not limited in their location at apparent thicknesses within contact lens 600, are not limited to symmetrical configurations, are not limited to uniform thickness distributions, and are not limited to a central location relative to the geometric center of contact lens 600. For example, additional layers or deeper or shallower arrangements of layers may be employed, or localized arrangements may be employed. In this manner, the lens may be customized to include multiple and various layers, and the thickness of the layers may be determined to provide a desired transmission rate of oxygen and water.

Various manufacturing methods may be used to manufacture the composite films and contact lenses disclosed herein. For example, contact lenses may be manufactured at least in part by forming, including cast forming and compression forming. Melt pressing and solution casting may also be performed, at least in part, to manufacture contact lenses. Additionally, the contact lens may be manufactured at least in part by machining (lathing).

The different materials from which the material film, composite film and/or contact lens are made may have different moduli. The modulus or more specifically the elastic modulus of a material is a measure of the resistance of the material to elastic deformation. In certain embodiments, the modulus of the primary material film is greater than the modulus of the secondary material film. In an alternative embodiment, the modulus of the primary material film is less than the modulus of the secondary material film.

In addition to providing a contact lens having a minimum transmission rate for the permeate oxygen, the contact lens may also have a minimum transmission rate for the permeate, e.g., carbon dioxide. In this case, the layer of the material film and/or the thickness of the contact lens is set to a minimum carbon dioxide transmission rate, but not or in addition to a minimum oxygen transmission rate.

The same principles discussed above also provide for delivery of therapeutic agents. The therapeutic agent delivery device comprises a composite membrane, wherein the composite membrane comprises one or more layered primary material membranes and one or more layered secondary material membranes, wherein the composite membrane has a thickness, a permeability to a first permeate, and a permeability to a second permeate; wherein the primary material membrane and the secondary material membrane each have a thickness, a permeability to a first permeate, and a permeability to a second permeate; wherein the thickness of the composite comprises the combined thicknesses of the primary material layer and the secondary material layer, wherein the thickness of the primary membrane and the thickness of the secondary membrane are such that the difference between the permeability of the composite membrane to the first permeate and the permeability of the primary material membrane to the first permeate is less than the difference between the permeability of the composite membrane to the second permeate and the permeability of the primary material membrane to the second permeate. In such embodiments, the second permeate is a therapeutic substance.

It should be understood that while various embodiments of the present invention are described herein in greater detail, the invention is illustrated by way of example only and that variations and modifications thereof are possible without departing from the subject matter within the scope of the appended claims, and their reasonable equivalents, which claims are to be construed as the present invention.

Claims

1. A contact lens, comprising:

an anterior surface distal to the eye;

a posterior surface facing the eye;

an intermediate positioned between the front surface and the back surface, wherein the intermediate has an oxygen permeability and a water permeability;

the thickness of the intermediate provides a water transmission rate less than a maximum value while providing an oxygen transmission rate greater than a minimum value;

wherein the maximum value of the water transmission rate is 13887.5Barrers/cm, and wherein the minimum value of the oxygen transmission rate is 24.1 x 10 ^-9 (cm×ml O ₂ )/(sec×ml×mmHg)；

Wherein the intermediate comprises a polymer comprising cross-linked polydimethylsiloxane.

2. The contact lens of claim 1 wherein the intermediate has a water permeability of less than 20,000 Barrers.

3. The contact lens of claim 1, wherein the intermediate has an oxygen permeability greater than 200 Barrers.

4. The contact lens of claim 1, wherein a region of the contact lens measured as an intermediate greater than 50 square millimeters has a thickness of the intermediate that provides a water transmission rate less than a maximum value while providing an oxygen transmission rate greater than a minimum value.

5. The contact lens of claim 1, wherein the average thickness of the contact lens is greater than 0.4 millimeters.

6. The contact lens of claim 1, wherein the average thickness of the contact lens is greater than 0.3 millimeters.

7. The contact lens of claim 1, wherein the average thickness of the contact lens is greater than 0.2 millimeters.