FLUID MODULATED INTRAOCULAR LENS

Abstract: A variable focus intraocular lens (56) is provided that is a compound lens formed of two or more lenses (58, 60) attached together, and enclosing one or more closed central spaces or compartments (64) therebetween. When the lens is implanted inside the eye, the central space(s) contain sterile air, gas, and/or are at a reduced pressure (vacuum). If the power of the variable focus intraocular lens is to be changed, one or more of the central space(s) is opened (67) so that the aqueous humor enters the targeted lens compartment, and changes the power of the intraocular lens. The compartment can be opened either with a laser or surgically, e.g., through a weakened thin place in the wall of the central compartment, by removing a plug, by opening a valve, or the like.

Description: FLUID MODULATED INTRAOCULAR LENS BACKGROUND AND SUMMARY OF THE INVENTION A fluid modulated lens is a compound lens formed from two lenses enclosing a central compartment therebetween. FIGURE 1 illustrates the structure of a typical fluid modulated lens. As shown therein, the typical fluid modulated lens has four refractive surfaces A, B, C, and D. The two internal surfaces B and C form the boundary of the central compartment F. The overall power of the lens depends on the refractive index of the refractive medium present in the center compartment F and on the power of the refractive surfaces B and C. Thus, the power of the lens will depend on whether the central reservoir is filled with gas or liquid. More particularly, considering that the refractive index of transparent material used to make lenses, i.e., glass, plastic acrylic, hydrogel, silicon, etc. is 1.5, the refractive index of most liquids is around 1.3, and the refractive index of air and most gases is 1.0, a central compartment F filled with gas leads to greater refraction of light at the refractive surfaces B and C than when filled with liquid. This is because when the central compartment is filled with gas, the difference between the refractive indices of the lens material and the gas is 1.5 - 1.0 = 0.5, whereas if the central compartment is filled with liquid, the difference between the refractive index of the lens material and the liquid is 1.5 - 1.3 = 0.2. Thus, when the central compartment is filled with liquid, the power of the two internal surfaces B and C is 0.2 ÷ 0.5 = 0.4 times the power when the central compartment was filled with air, so if the sum of powers of the two refractive surfaces B and C is negative, the power of the lens is increased, and if the sum of powers of B and C is positive the overall power of the lens is decreased. By way of example, consider a case where the central compartment of the fluid modulated lens is filled with a gas (FIGURE 1). Assuming the powers of the refractive surfaces A, B, C, and D are +5, +5, +5, and +5 diopters, respectively, then the overall power of the lens is 20 diopters. Now consider the case where the central compartment of that fluid modulated lens is filled with a liquid (FIGURE 2). As noted above, the powers of the refractive surfaces B and C will be 0.4 of their original power (the power when gas is disposed in the central compartment), so the power of each of B and C will be 0.4 x 5 = 2 diopters. Therefore, the powers of the refractive surfaces A, B, C, and D would be +5, +2, +2 and +5 diopters, respectively, so the overall power of the lens would be 14 diopters. In cataract surgery, the human crystalline lens is removed and is replaced with an artificial lens. Conventionally, this artificial lens has a fixed power and that power cannot be changed after it is implanted inside the eye. In children, development of the visual area in the brain is stimulated by sharp vision. As the child grows, the eye grows. When the child has an implanted intraocular lens, then, the power of the intraocular lens should be decreased as the child grows to obtain/maintain sharp vision, otherwise the development of the visual area in the brain may cease or be retarded. Thus, in the first 8 years of life the power of the intraocular lens should be decreased at least once, preferably twice. Heretofore, this requires difficult surgery to replace the intraocular lens with a new one having a lower power. In accordance with the invention, the principle of fluid modulated lenses is used to provide variable focus intraocular lenses, so that the power of the lens can be changed after the lens has been implanted in the eye. As is apparent from the discussion above, the invention may be used to particular advantage in pediatric cataract surgery. In accordance with the invention, the implanted intraocular lens is comprised of two or more lenses having at least one compartment defined therebetween. When it is deemed necessary or desirable to change the power of the intraocular lens, instead of the conventional replacement surgery, the power of the variable focus intraocular lens is changed by changing the fluid in the chamber of the intraocular lens, for example by perforating a wall of the intraocular lens so that fluid disposed within the eye flows into the intraocular lens cavity. In an exemplary embodiment, the wall is perforated using a laser and, therefore, there is no need for surgery. In accordance with another exemplary implementation of the invention, the variable focus intraocular lens can be used in adults to change the astigmatic element after the cataract wound heals. More specifically, conventionally the ophthalmologist can calculate the spherical power of the intraocular lens needed for the cataract patient, but the astigmatism depends on the healing of the cataract wound. Wound healing is variable from one person to another so the astigmatism varies, and most cataract patients need glasses to correct this astigmatic element. Variable focus intraocular lenses provided in accordance with the invention can be used in adults to change the astigmatic element after the cataract wound heals. This may be done using a laser with no surgical intervention and postoperative glasses may not be needed. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic illustration of a typical fluid modulated lens; FIGURE 2 illustrates the lens of FIGURE 1 with a liquid in the central compartment; FIGURE 3 schematically shows a variable focus intraocular lens embodying the invention; FIGURE 4 illustrates the variable focus intraocular lens of FIGURE 3 with a liquid disposed in the central compartment; FIGURE 5 schematically shows the optics of another variable focus intraocular lens provided in accordance with the invention; FIGURE 6 schematically shows the same variable focus intraocular lens as FIGURE 5 with one central compartment filled with fluid; FIGURE 7 shows the same variable focus intraocular lens as FIGURE 6 with the second central compartment filled with fluid; FIGURE 8 is an anterior view of an intraocular lens provided in accordance with the invention; FIGURE 9 is a schematic elevational view of a first intraocular lens assembly corresponding to the configuration of FIGURE 8; FIGURE 10 is a schematic elevational view of an alternate intraocular lens assembly corresponding to the configuration of FIGURE 8; FIGURE11 is a schematic cross-sectional view showing the intraocular lens of FIGURES 8-9 mounted within the eye; FIGURE 12 is a view similar to FIGURE 11 wherein the intraocular lens cavity has been filled with eye fluid; FIGURE 13 is a schematic cross-sectional view showing an alternate intraocular lens in accordance with the invention, disposed within the eye; FIGURE 14 is a schematic cross-sectional view showing another alternate intraocular lens in accordance with the invention, disposed within the eye; FIGURE 15 is a schematic cross-sectional view showing yet an alternate intraocular lens in accordance with the invention, disposed within the eye; FIGURE 16 is a schematic cross-sectional view showing a further alternate intraocular lens embodying the invention, disposed within the eye; FIGURE 17 is a schematic cross-sectional view showing yet a further alternate intraocular lens in accordance with the invention, disposed within the eye; and FIGURE 18 is a schematic cross-sectional view showing another alternate intraocular lens embodying the invention, disposed within the eye. DETAILED DESCRIPTION OF THE INVENTION The variable focus intraocular lenses provided in accordance with the presently preferred, exemplary embodiments of the invention are compound lens formed of two or more lenses attached together and enclosing one or more closed central spaces therebetween. When the lens is implanted inside the eye, the central space(s) contain sterile air, gas and/or are at a reduced pressure (vacuum). If the power of the variable focus intraocular lens is to be changed, one or more of the central space(s) is opened so that the aqueous humor (regular fluid present inside the eye) enters the central lens compartment, and changes the power of the intraocular lens. A central compartment can be opened either with a laser or surgically, e.g., through a weakened thin place in the wall of the central compartment, by removing a plug, by opening a valve, or the like. For example, in an outpatient clinic regular lasers used in ophthalmology can be used to change the power of the intraocular lens. More particularly, a YAG laser produces a localized explosion inside the eye disrupting the structures around the explosion. The magnitude and site of the explosion are controlled to the nearest micron. Thus, in accordance with an exemplary implementation of the invention, the aiming beam is focused on a target portion of the wall of the central compartment of the lens and the laser is fired to make a hole in the wall of the central compartment. If the central compartment of the variable focus intraocular lens contains a vacuum, the eye fluid enters the central compartment and changes the power of the intraocular lens. If the central compartment of the lens contains air or gas that is not under vacuum, the fluid will never the less enter the central compartment and the air or gas will dissolve in the eye fluid (aqueous humour), so that the lens central compartment will ultimately be filled with liquid. Argon, Krypton and Diode lasers can also be used to change the power of the variable focus intraocular lens but they are only absorbed by colored objects. Therefore, consistent with the intended use of such lasers, certain target area(s) in the wall(s) of the central compartment(s) must be appropriately colored so that they can absorb the laser. When laser is directed to those tinted areas, the areas absorb the laser and melt so that a hole is formed. Mathematical Proof: Considering the refractive index of air is 1.00, most materials used in intraocular lens manufacture have a refractive index of about 1.5, while most transparent liquids have a refractive index around that of water, which is 1.3. Diopteric power of a refractive surface = (Difference in refractive indices of the surrounding media) ÷ (Radius of curvature of the refractive surface in meters) Diopteric power of a refractive surface between air and intraocular lens (Refractive index of intraocular lens material - refractive index of air) ÷ (Radius of curvature of the refractive surface in meters) = (1.5-1.0) ÷ R 0.5 R Diopteric power of a refractive surface between eye fluid (aqueous humor) and intraocular lens = (Refractive index of intraocular lens material(1.5) - refractive index of eye fluid (aqueous)(1.3)) ÷ (Radius of curvature of the refractive surface in meters (R)) = 0.2 R (Diopteric power of a refractive surface between liquid and intraocular lens material) ÷ (Diopteric power of refractive surface between air and intraocular lens material)= .02 0.5 : = 0.4 R R FIGURE 3 schematically shows the optics of a variable focus intraocular lens 10 embodying the concept of the invention, having four refractive surfaces 12, 14, 16, 18 and a central compartment 20. The wall 22 of the peripheral part of the central compartment 20 is thinned so that it can be perforated surgically or by laser. The power of the refractive surfaces 12 and 18 will be fixed as, in use, they are always in contact with liquid inside the eye. The powers of the refractive surfaces 14 and 16 depend on the content of the central compartment 20. If the central compartment 20 contains air, as schematically shown in FIGURE 3, the power is maximized, and if it contains a liquid, as schematically shown in FIGURE 4 the power is decreased accordingly. Considering a numerical example where the variable focus intraocular lens is surrounded by the eye fluid 24 (aqueous), at the outset, the central compartment 20 is filled with air 26. The powers of the refractive surfaces 12, 14, 16, and 18 are 10, 5, 5, and 10 diopters respectively. The overall power of the lens is 10 + 5 + 5 + 10 = 30 diopters. A flow path is then opened, e.g. by forming a hole 28 in the lens wall 22, to fluidly connect the central compartment 20 to the eye fluid 24 (aqueous), so that the central compartment 20 is fills with liquid, shown schematically at 30. The powers of the refractive surfaces 12 and 14 are reduced in this example to 2 diopters each (0.4 of their original value, as calculated herein above) so the overall power of the variable focus intraocular lens is decreased to 10 + 2 + 2 + 10 = 24 diopters. FIGURE 5 schematically shows the optics of a variable focus intraocular lens 32 having six refractive surfaces, 34, 36, 38, 40, 42, 44 and two central compartments 46, 48 which are normally filled with sterile air. Filling central compartment 46 with eye fluid (aqueous) decreases the numerical value of the refractive surfaces 36 and 38. Filling the central compartment 48 with eye fluid (aqueous) decreases the numerical value of the refractive surfaces 40 and 42. Exemplary powers for these refractive surfaces and the overall power of the lens are listed below. 34= +10; 36= +2 axis 180; 38 = 0; 40 = 0; 42 = +2 axis 90; 44 = +10; Total power of the intraocular lens = 22 diopters. FIGURE 6 shows the same variable focus intraocular lens 32 shown in FIGURE 5, but a fluid passage 50 has been opened, i.e., a hole has been created, between the eye fluid 52 and the central compartment 46. The powers of the refractive surfaces and the overall power of the lens are listed below. 34 = +10; 36 = +2 axis 180 X 0.4=0.8 axis 180; 38 = 0; 40 = 0; 42 = +2 axis 90; 44 = +10; Total power of the intraocular lens = 20.8 spherical diopter and 1.2 cylinder diopter axis 90. FIGURE 7 shows the same variable focus intraocular lens 32 shown in FIGURE 6, but a fluid passage 54 has been opened, i.e., a hole has been created, between the eye fluid 52 and the central compartment 48. The powers of the refractive surfaces and the overall power of the lens are listed below. 34 = +10; 36 = +2 axis 180 X 0.4= 0.8 axis 180; 38 = 0; 40 = 0; 42 = +2 axis 90 X 0.4 = 0.8 axis 90; 44 = +10; Total power of the Intraocular lens = 20.8 spherical diopters. Referring now to FIGURES 8-12, a fluid modulated intraocular lens 56 provided in accordance with the present invention is shown. The air filled intraocular lens of this embodiment is formed of two lenses 58, 60 attached together by a thin diaphragm 62 enclosing a small compartment 64 therebetween. Compartment 64 initially contains sterile air which may be under negative pressure (vacuum). Conventional haptics 66 are provided to keep the intraocular lens in place inside the eye. The diaphragm 62 may be attached to both lenses as shown in FIGURE 9, or it may be a projection 62' from one lens 58' that is attached to the other lens 60', as shown in FIGURE 10. In FIGURE 11 , the intraocular lens 56 is shown implanted inside the eye, with the central compartment 64 filled with sterile air. When the power of the intraocular lens is to be modified, a flow passage is opened as at 67 so that fluid can flow from the interior of the eye into compartment 64. The flow passage may be a perforation that is generated surgically with a small needle or non-surgically with a laser, a pre-plugged passage that is opened with a laser or surgically, a valve that is opened, etc. Thereafter, the air is absorbed and the compartment 64 between the two lenses 58,60 becomes filled with eye fluid (aqueous humour). If Argon, Krypton or Yag laser is used, the perforation of the diaphragm is made easier by pigmenting it to increase its laser absorption or designing ultra thin parts in the diaphragm. FIGURE 13 shows another embodiment in which the variable focus intraocular lens 68 is formed with more than two lenses, in this example, two bicovex 70, 72 and one planoconvex 74. In this case the lenses are attached together by a thin membrane 76 and define two air filled spaces 78 and 80. The lens 68 is kept in place with two haptics 82. FIGURE 14 shows another embodiment in which the variable focus intraocular lens 84 is formed of two lenses 86 (biconvex) and 88 (piano), attached together. The anterior lens 86 has a thin peripheral wall 90 that can be attacked by laser or opened surgically. A central space 92 is present between the two lenses 86, 88. Again, haptics 94 attach the lens inside the eye. FIGURE 15 shows yet another embodiment in which the air filled intraocular lens 96 is formed of two lenses 98 (concavoconvex) and 100 (biconvex) attached together. The posterior lens 100 has a thin peripheral wall 102 which is either a projection from one of the lenses to the other or a diaphragm extending between the two lenses, that can be attacked by laser or opened surgically. A central space 104 is defined between the two lenses and is filled with fluid when a fluid flow path is opened between the interior of the eye and the cavity 104. FIGURE 16 shows yet another embodiment in which the variable focus intraocular lens 106 is formed of two lenses I08 (biconvex) and 110 (biconvex) attached together. A thin peripheral wall 11 1 is protruded, either as a projection from one of the lenses, as shown, or as a diaphragm extending between the two lenses, and can be attacked by laser or opened surgically. A central space 112 is present between the two lenses for being filled with fluid. FIGURE 17 shows variable focus intraocular lens 114 formed of three lenses 116, 118, 120, two bi-convex and one piano, defining two compartments 122 and 124. The periphery of lens 116 may be thinned so that attacking it by laser or surgically opens space 122, or the lens connecting wall 126 may be perforated to fill space 122. Space 124 is opened either by perforating a thin peripheral part of lens 118 or 120, or by suitably perforating the lens connecting wall 128 therebetween. FIGURE 18 shows another variable focus intraocular lens 130 formed of three lenses 132, 134, 136, two planoconvex and one biconvex defining two compartments 138, 140. The periphery of lens 132 is thinned so that attacking it by laser or surgically opens space 138. Space 140 is opened either by perforating the thin peripheral part of lens 136, perforating a thin peripheral part of lens 134, if lens 132 is perforated, or perforating the lens connecting wall 142. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Thus, while the invention has been described with reference to particular types and combinations of lens elements, it is to be understood that the invention could be applied to any of a number of combinations of lenses of various types, including piano, biconvex, planoconvex, concavoconvex, biconcave, planoconcave and toric.

Claims: I Claim: 1. An intraocular lens for implantation into a human eye, comprising: a lens assembly including at least two lens elements disposed in generally side-by-side, parallel, spaced apart relation so as to define a gap therebetween, a connecting wall extending between said lenses so as to define at least one sealed compartment between said at least two lens elements, at least a portion of said connecting wall being perforable by laser or having a selectively opened passage defined therethrough, whereby a flow passage can be opened for flowing a fluid from an exterior of said compartment into an interior of at least one compartment, whereby a power of the lens assembly defined by at least two lenses and at least one compartment defined therebetween is selectively changed. 2. An intraocular lens as in claim 1 , wherein said connecting wall is formed separately from at least one of said lenses and connected thereto. 3. An intraocular lens as in claim 1 , wherein at a sterile gas is disposed in said compartment. 4. An intraocular lens as in claim 1 , wherein said compartment has a vacuum defined therewithin. 5. An intraocular lens as in claim 1 , wherein said connecting wall is perforated to define said flow passage and at least one plug is disposed to seal said perforation, said plug being adapted to be selectively displaced or destroyed with a laser or a surgical instrument to open said flow passage. 6. An intraocular lens as in claim 1 , wherein said connecting wall comprises a projection from an outer periphery of one of said lenses. 7. An intraocular lens as in claim 6, wherein said projection projects generally radially from a radially outer peripheral edge of said one lens. 8. An intraocular lens as in claim 1 , wherein said lenses comprising said lens assembly are selected from the group consisting of piano, biconvex, planoconvex, concavoconvex, biconcave, planoconcave and toric lenses. 9. An intraocular lens as in claim 1 , further comprising an attachment structure for retaining the lens assembly in place when implanted inside the eye. 10. An intraocular lens as in claim 1 wherein at least a portion of said connecting wall is colored so as to enhance absorption of laser light. 11. An intraocular lens as in claim 1 wherein a radially outer portion of at least one of said lenses is of reduced thickness so as to be selectively perforable with one of a laser and a surgical instrument. 12. A method of varying a power of an intraocular lens comprising: providing an intraocular lens including: a lens assembly including at least two lens elements disposed in generally side-by-side, parallel, spaced apart relation so as to define a gap therebetween, connecting wall extending between said lenses so as to define at least one sealed compartment between said at least two lens elements, implanting said intraocular lens in a human eye by inserting said intraocular lens through a surgical incision in the eye; allowing said incision to heal; opening a flow passage through said connecting wall so as to i allow fluid to flow from an interior of the human eye into said at least one compartment, whereby a power of the lens assembly defined by at least two lenses and at least one compartment defined therebetween is selectively changed. 13. A method as in claim 12, wherein when said intraocular lens is implanted, a sterile gas is disposed in said compartment. 14. A method as in claim 12, wherein when said intraocular lens is implanted, said compartment has a vacuum defined therewithin. 15. A method as in claim 12, wherein said connecting wall is pre- perforated to define said flow passage and at least one plug is disposed to seal said perforation, and said step of opening comprises displacing or destroying said plug with a laser or a surgical instrument to open said flow passage. 16. A method as in claim 12, wherein said lenses comprising said lens assembly are selected from the group consisting of piano, biconvex, planoconvex, concavoconvex, biconcave, planoconcave and toric lenses. 17. A method as in claim 12, wherein said step of opening comprises aiming a laser at one of said connecting wall and a thinned peripheral portion of one of said lenses and firing said laser so as to define a hole therein. 18. A method as in claim 17, wherein at least a portion of said connecting wall is colored so as to enhance absorption of laser light.

Inventors: AYOUB ADHAM, AYOUB, ADHAM
Applicants: UNIV JOHNS HOPKINS, JOHNS HOPKINS UNIVERSITY
Application year: 1999
Main classification: A61F2
IPC codes: A61F2