Title:
Intraocular lens adapted for accommodation via electrical signals
Kind Code:
A1


Abstract:
A lens system is provided. The lens system can include a lens adapted to be part of the optical pathway of an eye and a sensor. The sensor is adapted to sense a condition. The lens system also includes a control unit. The control unit is adapted to receive a signal from the sensor. The signal includes information about the condition. The control unit is operable to alter the shape of the lens based at least partly upon the condition. The lens can be adapted for positioning inside the capsular bag of the eye, in the posterior chamber of the eye, in place of the capsular bag of the eye or in the cornea. The sensor can be a tension sensor. The condition can be the amount of tension at the zonules of the eye. The control system can include a fluidic pressure generator and a fluid flow control device.



Inventors:
Peyman, Gholam A. (Sun City, AZ, US)
Application Number:
11/259781
Publication Date:
05/03/2007
Filing Date:
10/27/2005
Primary Class:
Other Classes:
623/6.37
International Classes:
A61F2/16
View Patent Images:



Primary Examiner:
PRONE, CHRISTOPHER D
Attorney, Agent or Firm:
POLSINELLI PC ((DC OFFICE) 1000 Louisiana Street Suite 6400, HOUSTON, TX, 77002, US)
Claims:
1. A lens system comprising: a lens positioned within an eye; and a control unit, wherein said control unit is operable with said lens to alter the focal length of said lens based at least partly upon a condition.

2. The lens system of claim 1, wherein said lens is adapted for positioning at a location selected from the group consisting of inside the substantially capsular bag of the eye, inside the capsular bag of the eye in which an anterior portion of the capsular bag around the optical axis of the eye is removed, inside the capsular bag of the eye in which a posterior portion of the capsular bag around the optical axis of the eye is removed, the posterior chamber of the eye, the anterior chamber of the eye, in place of the capsular bag of the eye, and the cornea.

3. The lens system of claim 1, further comprising: a sensor, wherein said sensor is adapted to sense the condition and wherein said control unit is adapted to receive a signal from said sensor, wherein the signal includes information about the condition.

4. The lens system of claim 3, wherein said condition is the amount of tension at the zonules of the eye.

5. The lens system of claim 1, wherein said control system is operable with said lens to alter the focal length of said lens by passing a current through said lens.

6. The lens system of claim 1, wherein said control system includes a fluidic pressure generator and a fluid flow control device, wherein said lens includes a chamber adapted to receive a fluid, and wherein said control system is operable with said lens to alter the focal length of said lens by changing the fluidic pressure in the chamber.

7. The lens system of claim 6, wherein the chamber is at least partly enclosed by a flexible membrane.

8. A lens comprising: a chamber adapted to house a substance, said lens being adapted to be positioned in an eye, wherein said lens is coupled to a control unit, wherein the control unit is operable to control the focal length of said lens by influencing the substance.

9. The lens of claim 8, wherein influencing the substance includes applying an electrical field across the substance.

10. The lens of claim 8, wherein influencing the substance includes changing the pressure of the substance in the chamber.

11. The lens of claim 8, wherein the control unit receives a signal from a sensor, wherein the signal includes information about a condition.

12. The lens of claim 11, wherein the condition is the amount of tension at the zonules of the eye.

13. A control unit comprising: an electronic circuit; wherein said control unit is coupled to a lens, said lens including a chamber, which is adapted to house a substance, said lens being adapted to be positioned in an eye, said electronic circuit being operable to control the focal length of the lens.

14. The control unit of claim 13, wherein said electronic circuit being operable to control the focal length of the lens by applying an electric field to the substance.

15. The control unit of claim 13, wherein said electronic circuit receives a signal from a sensor, wherein the signal includes information about a condition.

16. The control unit of claim 15, wherein the condition is the amount of tension at the zonules of the eye.

17. An intraocular lens, comprising: a lens body; and a control system adapted to alter the refractive properties of the lens body such that the lens body at least partly assists in accommodation.

18. The intraocular lens of claim 17, wherein the control system is adapted to alter the refractive properties of the lens body by altering the shape of the lens body.

19. The intraocular lens of claim 17, wherein the control system is adapted to alter the shape of the lens body by altering the fluidic pressure in at least one chamber in the lens body.

20. The intraocular lens of claim 17, wherein the control system is adapted to alter the refractive properties of the lens body by altering the refractive index of at least one portion of the lens body.

21. A lens system comprising: a lens positioned along the optical path of an eye; and a control unit, wherein said control unit is operable with said lens to alter the focal length of said lens based at least partly upon a condition.

22. The lens of claim 21, wherein said lens is positioned within the eye.

23. The lens of claim 21, wherein the control unit is operable to alter the focal length of said lens in response to a manual input.

24. The lens of claim 21, wherein the control unit is operable to automatically alter the focal length of said lens.

Description:

BACKGROUND

An eye can have various disorders which affect the crystalline lens of the eye. One of the most common disorders is cataracts, which is a clouding of the crystalline lens. The conventional treatment for cataracts is removal of the crystalline lens and replacement of the lens with an artificial or intraocular lens (IOL).

Once an IOL is implanted, however, it generally has a fixed refractive power. This presents a problem with respect to both far and near vision. With respect to far vision, the diopter power of the IOL is generally not capable of perfect vision—i.e. 20/20. This problem is due to the fact that the refractive power of the IOL must be chosen prior to implantation and thus can only be approximated. Since the diopter power can only be approximated, most patients will require at least a ±1.00 diopter power correction along the optical path to provide perfect vision. With respect to near vision, an artificial lens results in a loss of accommodation (i.e., the process of focusing the eye between far objects and near objects).

SUMMARY

In one embodiment, a lens system is provided. The lens system includes a lens adapted to be part of the optical pathway of an eye and a sensor. The sensor is adapted to sense a condition. The lens system also includes a control unit. The control unit is adapted to receive a signal from the sensor. The signal includes information about the condition. The control unit is also operable with the lens to alter the shape of the lens based at least partly upon the condition.

The lens can be adapted for positioning inside the capsular bag of the eye, in the posterior chamber of the eye, in place of the capsular bag of the eye or in the cornea. The sensor can be a tension sensor. The condition can be the amount of tension at the zonules of the eye. The control system can be operable with the lens to alter the shape of the lens by passing a current through the lens. The control system can include a fluidic pressure generator and a fluid flow control device. The lens can include a chamber adapted to receive a fluid. Further, the control system can be operable with the lens to alter the shape of the lens by changing the fluidic pressure in the chamber. The fluid can be a sodium chromate solution. The chamber can be at least partly enclosed by a flexible membrane. The sensor can be a wireless signal receiver.

In another embodiment, a lens is provided. The lens includes a flexible membrane and a chamber adapted to receive a fluid. The flexible membrane is adapted to at least partly enclose the chamber. The lens is adapted to be part of the optical pathway of an eye. The chamber is fluidly coupled to a control unit, and the control unit is operable to control the fluidic pressure inside the chamber.

The fluid can be a sodium chromate solution. The control unit can receive a signal from a sensor, wherein the signal includes information about a condition. The sensor can be a tension sensor. The condition can be the amount of tension at the zonules of the eye. The sensor can be a wireless signal receiver.

In another embodiment, a control unit is provided. The control unit includes a fluidic pressure generator and an electronic circuit. The control unit is coupled to a lens, and the lens includes a chamber adapted to receive a fluid and a flexible membrane, wherein the flexible membrane is adapted to at least partly enclose the chamber. The lens is adapted to be part of the optical pathway of an eye. The chamber is fluidly coupled to the fluidic pressure generator, and the electronic circuit is operable to control the fluidic pressure generator. The fluidic pressure generator is operable to change the fluidic pressure inside the chamber.

The fluid can be a sodium chromate solution. The electronic circuit can receive a signal from a sensor, wherein the signal includes information about a condition. The sensor can be a tension sensor. The condition can be the amount of tension at the zonules of the eye.

Additional features and advantages are described herein, and will be apparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side elevational view in section taken through the center of an eye showing the cornea, pupil, crystalline lens, and capsular bag.

FIG. 2 is a side elevational view in section of the eye shown in FIG. 1 showing the capsular bag after removal of the crystalline lens.

FIG. 3 is a side elevational view in section of the eye shown in FIG. 2 showing the treatment of the interior of the capsular bag with a liquid to prevent capsular opacification.

FIG. 4 is a side elevational view in section of the eye shown in FIG. 3 showing placement of a replacement lens into the capsular bag.

FIG. 5 is a side elevational view in section of the eye shown in FIG. 3 in which a replacement lens is positioned in the capsular bag and a fluidic system and remote power unit are positioned in the posterior chamber.

FIG. 6 is a flow chart of the process of accommodation in accordance with one embodiment of the present invention.

FIG. 7 is a flow chart of the process of accommodation in which the fluidic system includes a pressure sensor for sensing the pressure in at least one of the chambers in accordance with one embodiment of the present invention.

FIG. 8 is a side elevational view in section of the eye shown in FIG. 3 in which a replacement lens is positioned in the capsular bag and a power unit is positioned in the posterior chamber.

FIG. 9 is a flow chart of the process of accommodation in response to electrical signals in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

In various embodiments, a lens capable of accommodation in response to electrical signals is provided. The lens can be placed at any suitable location along the optical path of an eye, including but not limited to within the capsular bag, in place of the capsular bag, within the posterior chamber or on, in or behind the cornea. Further, it should be noted that any suitable section of the capsular bag can be removed, including but not limited to an anterior portion or a posterior portion around the main optical axis of the eye. The lens is preferably coupled to a fluidic pumping system which is also coupled to a control system which preferably includes a power source and a signal generation unit.

Referring initially to FIG. 1, a normal eye 10 has a cornea 12, an iris 14, and a crystalline lens 16. The crystalline lens 16 is contained within a capsular bag 18 that is supported by zonules 20. The zonules 20, in turn, are connected to the ciliary muscle 22. According to Helmholz's theory of accommodation, upon contraction of the ciliary muscle 22, the tension on the zonules 20 is released. The elasticity of the lens causes the curvature of the lens 16 to increase, thereby providing increased refractive power for near vision. Conversely, during dis-accommodation, the ciliary muscle 22 is relaxed, increasing the tension on the zonules 20 and flattening the lens 16 to provide the proper refractive power for far vision.

If the electrically accommodating lens is to be positioned within the capsular bag and, thus, replace the crystalline lens, a suitable first step is to remove the existing lens. As illustrated in FIG. 2, the lens is preferably removed using any technique which allows removal of the lens through a relatively small incision, preferably about a 1-2 mm incision. The preferred method is to create a relatively small incision 24 in the cornea 12 and then perform a capsulorhexis to create an opening 26 into the anterior side 28 of the capsular bag 18. An ultrasonic probe 30 is inserted into the capsular bag 18 through the opening 26. The probe's vibrating tip 32 emulsifies the lens 16 into tiny fragments that are suctioned out of the capsular bag by an attachment on the probe tip (not shown). Alternatively, the lensectomy may be performed by laser phacoemulsification or irrigation and aspiration.

Once the crystalline lens 16 has been removed, the capsular bag 18 can be treated to help prevent a phenomenon known as capsular opacification. Capsular opacification is caused by the proliferated growth of the epithelial cells on the lens capsule. This growth can result in the cells covering all or a substantial portion of the front and rear surfaces of the lens capsule, which can cause the lens capsule to become cloudy and thus adversely affect the patient's vision. These cells can be removed by known techniques, such as by scraping away the epithelial cells; however, it is often difficult to remove all of the unwanted cells. Furthermore, after time, the unwanted cells typically grow back, requiring further surgery. To prevent capsular opacification, the capsular bag 18 is preferably treated to eliminate the proliferated growth of epithelial cells, as described below.

As seen in FIG. 3, one method of treating the epithelial cells to prevent capsular opacification is to use a cannula 34 to introduce a warm liquid 36 (preferably about <60° C.) into the capsular bag 18, filling the capsular bag 18. The liquid contains a suitable chemical that kills the remaining lens cells in the capsular bag and also cleans the interior of the capsular bag. Suitable chemicals, as well as other suitable methods of treatment that prevent capsular opacification are disclosed in U.S. Pat. No. 6,673,067 to Peyman, which is herein incorporated by reference in its entirety.

As shown in FIG. 4, a replacement lens 38 is then positioned within the capsular bag 18. Preferably, the lens 38 can be folded or rolled and inserted through the incision in the capsular bag 18; however, the lens 38 can be rigid and/or can be inserted through a larger second incision in the capsular bag 18 or the initial incision, possibly after the initial incision is widened, or in any other suitable manner. Preferably the lens 38 varies its focal length in response to changes in fluidic pressure within the lens made in accordance with electrical signals; however the lens 38 can change its index of refraction or alter its focal length in any other suitable manner. Since the capsular bag 18 is still in place, the capsular bag can still assist in accommodation; however, it is not necessary for capsular bag 18 to assist with accommodation. The lens, as shown in FIG. 5, preferably includes two chambers 40 set on opposite sides of a substrate 42 and covered with a flexible membrane 44; however, the lens can have one or any other suitable number of chambers. Preferably, the two chambers 40 contain a fluid 46, and preferably the fluid 46 is a sodium chromate solution; however, if desired, one or more of the chambers can contain something other than a fluid or the chambers can contain different fluids or different sodium chromate solutions. The substrate 42 is preferably glass; however, the substrate 42 can be any suitable material. Preferably, the flexible membrane 44 is a biocompatible material; however, the flexible membrane can be any suitable material.

Preferably, the fluidic pressure within the chambers 40 can be altered using a fluidic system 48 which includes a miniature fluidic pressure generator (e.g., a pump or any other suitable device), a fluid flow control device (e.g., a valve or any other suitable device), a control circuit and a pressure sensor; however, the fluidic pressure can be altered in any suitable manner. Further, if desired, a fluidic system 48 does not need a pressure sensor. When subjected to electrical signal, the electronic control circuit of the fluidic system 48 controls the valves and pumps to adjust the fluidic pressure in one or more of the chambers 40. Preferably, the fluidic pressure is adjusted by pumping fluid in or releasing a valve to allow fluid to flow out and back into the system 48; however, the fluidic pressure can be adjusted by pumping fluid out or in any other suitable manner. As a result, the shape and the focal length of the lens 38 is altered, providing accommodation. Lenses that similarly change focal length in response to fluidic pressure changes made in accordance with electrical signals are described in greater detail in “Integrated Fluidic Adaptive Zoom Lens”, Optics Letters, Vol. 29, Issue 24, 2855-2857, December 2004, the entire contents of which is hereby incorporated by reference.

As shown in FIG. 5, fluidic system 48 is preferably positioned in the posterior chamber 50; however, the fluidic system 48 can be positioned outside the eye, within the sclera, between the sclera and the choroids or any other suitable location. Further, the fluidic system 48 is preferably positioned such that it is not in the visual pathway. A tube 52 fluidly connects the lens 38 and the fluidic system 48. Preferably, the tube 52 passes through a small incision in the capsular bag 18 near the connection of the zonules 20 and the capsular bag 18; however, the tube 52 can pass through the capsular bag in any suitable location.

Preferably, fluidic system 48 includes a power source which is preferably rechargeable through induction or other suitable means such as generating and storing electrical energy using eye and/or head movement to provide the energy to drive the generator; however, fluidic system 48 can be connected to a remote power source 54 as shown in FIG. 5 or to any other suitable power source. Preferably, the remote power source 54 is located in the posterior chamber 50; however, the remote power source 54 can be positioned outside the eye (e.g., under the scalp, within a sinus cavity, under the cheek, in the torso or in any other suitable location), within the sclera, between the sclera and the choroids or any other suitable location. Further, the remote power source 54 is preferably positioned such that it is not in the visual pathway. The remote power source 54 is preferably electrically coupled to the fluidic system 48 by electrically conductive line 56; however, the remote power source 54 can be coupled to the fluidic system 48 in any suitable manner. Further, the remote power source 54 preferably includes a signal generator which can supply control signals to the fluidic system 48 via electrically conductive line 56; however, the remote power source 54 can be without a signal generator, if desired, or can supply control signals to the fluidic system 48 in any suitable manner. Similar remote power sources are described in more detail in U.S. Pat. No. 6,947,782 to Schulman et al., which is herein incorporated by reference in its entirety.

Preferably, the remote power source 54 is coupled to a sensor 58 by electrically conductive line 60; however, the remote power source 54 can be coupled to sensor 58 in any suitable manner. The sensor 58 is preferably a tension sensor positioned on the zonules 20 so that the sensor 58 detects the amount of tension present in the zonules 20; however, the sensor 58 can be a wireless signal sensor, a neurotransmitter sensor, a chemical sensor, a pressure sensor or any other suitable sensor type and/or can be positioned in or near the ciliary muscle 22, at or near the nerve controlling the ciliary muscle 22, in the capsular bag 18 or in any other suitable location. Preferably, the sensor 58 detects the eye's attempt to cause its lens to accommodate; however, the sensor 58 can detect a manual attempt to accommodate the lens 38 (e.g., input through a wireless controller) or any other suitable input. The information detected at the sensor 58 is relayed to the remote power source 54 via line 60, and the signal generator of the remote power source 54 generates a signal in accordance with the information. The signal is sent to the fluidic system 48, which adjusts the fluidic pressure in one or more of the chambers 40 accordingly. Thus, the eye's natural attempts to focus will result in accommodation of lens 38. Response of lens 38 may vary from that of the natural lens; however, the neural systems which control the ciliary muscle 22 (and therefore the tension on the zonules 20), are provided with feedback from the optic nerve and visual neural pathways. As a result, the neural system can learn and adjust to the characteristics of the lens 38.

The process of accommodation in accordance with one embodiment is shown in FIG. 6. At step 600, the eye attempts to refocus at a different distance, and thus changes the tension on the zonules. At step 610, a tension sensor detects the new tension level and relays the information to a control unit. The control unit preferably includes a remote power source and a fluidic system; however, the control unit can include any suitable devices. At step 620, the control unit determines the correct adjustment to be made to the fluidic pressure in at least one chamber of a fluidic lens in response to the tension sensor information. At step 630, the control unit makes the determined fluidic pressure adjustment and the process repeats at step 600.

Another process of accommodation in accordance with another embodiment in which the fluidic system includes a pressure sensor for sensing the pressure in at least one of the chambers is shown in FIG. 7. At step 700, a user sends a signal to refocus his or her eye at a different distance. Preferably, the signal is sent wirelessly; however, the signal can be sent in any suitable manner. Further, the signal preferably includes information corresponding to the desired different distance; however, the signal can include information indicating only that the desired distance is closer or farther or any other suitable information. At step 710, a sensor detects the signal and relays the information to a control unit. The control unit preferably includes a remote power source and a fluidic system; however, the control unit can include any suitable devices. At step 720, the control unit determines a new fluidic pressure level to be created in at least one chamber of a fluidic lens in response to the sensor information. At step 730, the control unit increases or decreases, as appropriate given the current fluidic pressure as determined by the pressure sensor, the fluidic pressure in the chamber. At step 740 it is determined whether the desired fluidic pressure is equal to the pressure sensed by the pressure sensor. If the desired fluidic pressure is equal to the pressure sensed by the pressure sensor, at step 750, the lens is accommodated and the process repeats at step 700. If the desired fluidic pressure is not equal to the pressure sensed by the pressure sensor, the process repeats at step 730.

FIG. 8 illustrates an alternative accommodating lens 62. Lens 62 responds to electrical stimulation by changing its focal length. Similar to lens 38, lens 62 is preferably placed within the capsular bag 18; however, the lens 62 can be placed in the posterior chamber 50, in place of the capsular bag 18, within the cornea 12, on the surface of the eye or in any other suitable location. Further, it should be noted that any suitable section of the capsular bag can be removed, including but not limited to an anterior portion or a posterior portion around the main optical axis of the eye. If the lens 62 is placed within the capsular bag 18, the capsular bag can assist with accommodation; however, it is not necessary for the capsular bag 18 to assist with accommodation. Lens 62 may have one or more chambers that are at least partly filled with a fluid or other substance; however, lens 62 is not required to have a chamber.

Preferably, lens 62 is a fluid lens that alters its focal length by changing its shape; however lens 62 can be any suitable type of lens and can change its focal length in any suitable manner. The lens 62 preferably includes two immiscible (i.e., non-mixing) fluids of different refractive index (or other suitable optical property); however, the lens 62 is not required to include two immiscible fluids of different refractive index. Preferably, one of the immiscible fluids is an electrically conducting aqueous solution and the other an electrically non-conducting oil, contained in a short tube with transparent end caps; however, the immiscible fluids can be any suitable fluids and can be contained in any suitable container. The internal surfaces of the tube wall and one of its end caps are preferably coated with a hydrophobic coating that causes the aqueous solution to form itself into a hemispherical mass at the opposite end of the tube, where it acts as a spherically curved lens; however, the hydrophobic coating is not required and, if present, can be arranged in any suitable manner. Further, the coating can include any suitable material, including hydrophilic substances.

Preferably, the shape of the lens 62 can be adjusted by applying an electric field across the hydrophobic coating such that it becomes less hydrophobic (a process called “electrowetting” that results from an electrically induced change in surface-tension); however, the shape of the lens 62 can be adjusted by applying an electric field across any suitable portion of the lens 62. Preferably, as a result of this change in surface-tension, the aqueous solution begins to wet the sidewalls of the tube, altering the radius of curvature of the meniscus between the two fluids and hence the focal length of the lens. Increasing the applied electric field can preferably cause the surface of the initially convex lens to become less convex, substantially flat or concave; however increasing the applied electric field can cause the surface of the lens to change in any suitable manner. Preferably, decreasing the applied electric field has the opposite effect, enabling the lens 62 to transition smoothly from being convergent to divergent, or vice versa, and back again repeatably.

The lens 62 can measure 3 mm in diameter by 2.2 mm in length; however the lens 62 can have any suitable dimensions. The focal range of the lens 62 can be any suitable range and can extend to infinity. Further, switching over the full focal range can occur in less than 10 ms or any other suitable amount of time. Preferably, lens 62 is controlled by a DC voltage and presents a capacitive load; however, the lens 62 can be controlled by any suitable voltage and operate with any suitable electrical properties.

Lens 62 is electrically coupled to a power source 64 by electrically conductive line 66; however, lens 62 can be coupled to power source 64 in any suitable manner. Preferably, power source 64 is rechargeable through induction or other suitable means such as generating and storing electrical energy using eye and/or head movement to provide the energy to drive the generator; however, the power source 64 can be non-rechargeable, if desired. Similar to remote power source 54, the power source 64 is preferably located in the posterior chamber 50; however, the power source 64 can be positioned outside the eye (e.g., under the scalp, within a sinus cavity, under the cheek, in the torso or in any other suitable location), within the sclera, between the sclera and the choroids or any other suitable location. Further, the power source 64 is preferably positioned such that it is not in the visual pathway. The power source 64 preferably includes a signal generator which can supply current to the lens 62 via electrically conductive line 66; however, the power source 64 can be without a signal generator, if desired, or can supply control signals to the lens 62 in any suitable manner.

Preferably, the power source 64 is coupled to a sensor 68 by electrically conductive line 70; however, the power source 64 can be coupled to sensor 68 in any suitable manner. The sensor 68 is preferably a tension sensor positioned on the zonules 20 so that the sensor 68 detects the amount of tension present in the zonules 20; however, the sensor 68 can be a wireless signal sensor, a neurotransmitter sensor, a chemical sensor, a pressure sensor or any other suitable sensor type and/or can be positioned in or near the ciliary muscle 22, at or near the nerve controlling the ciliary muscle 22, in the capsular bag 18 or in any other suitable location. Preferably, the sensor 68 detects the eye's attempt to cause its lens to accommodate; however, the sensor 68 can detect a manual attempt to accommodate the lens 62 (e.g., input through a wireless controller) or any other suitable input. The information detected at the sensor 68 is relayed to the power source 64 via line 70, and the signal generator of the power source 64 generates a signal in accordance with the information. The signal is sent and passed through the lens 62, which preferably changes shape as a result of the electrical current flowing through it; however, the lens 62 could change its index of refraction in response to the electrical current flowing through it or change its focal length in any other suitable manner. Preferably, line 70 includes two separate electrical pathways that electrically couple to lens 62 at different, preferably substantially opposite, locations so that one of the pathways can serve as a ground wire; however, the lens 62 can be grounded in any other suitable manner to enable current supplied via line 70 to flow through the lens 62. As a result, similar to lens 38, the eye's natural attempts to focus will result in accommodation of lens 62. Response of lens 62 may vary from that of the natural lens; however, as with lens 38, the neural systems which control the ciliary muscle 22 (and therefore the tension on the zonules 20), are provided with feedback from the optic nerve and visual neural pathways. As a result, the neural system can learn and adjust to the characteristics of the lens 62.

The process of accommodation in response to electrical signals in accordance with one embodiment is shown in FIG. 9. At step 900, the eye attempts to refocus at a different distance, and thus changes the tension on the zonules. At step 910, a tension sensor detects the new tension level and relays the information to a control unit. The control unit preferably includes a power source; however, the control unit can include any suitable devices. At step 920, the control unit determines the correct adjustment to be made to the current being passed through the lens in response to the tension sensor information. At step 930, the control unit adjusts the current being passed through the lens and the process repeats at step 900.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.