| Solution for removing cataracts via liquefracture -> Monitor Keywords |
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Solution for removing cataracts via liquefractureRelated Patent Categories: Drug, Bio-affecting And Body Treating Compositions, Designated Organic Active Ingredient Containing (doai), Peptide Containing (e.g., Protein, Peptones, Fibrinogen, Etc.) Doai, Cyclopeptides, 25 Or More Peptide Repeating Units In Known Peptide Chain StructureSolution for removing cataracts via liquefracture description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070173448, Solution for removing cataracts via liquefracture. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a divisional of application Ser. No. 10/433,166 filed May 30, 2003, which itself claims priority from and incorporates by reference commonly owned PCT application Ser. No. US01/47635 filed Dec. 11, 2001, and provisional application Ser. No. 60/257,715, filed Dec. 20, 2000. BACKGROUND OF THE INVENTION [0002] The present invention is directed to the field of ophthalmic surgery. More specifically, the invention is directed to the field of procedures and associated products for removing the natural crystalline lens of the human eye in patients whose lenses have become afflicted with cataracts or other conditions wherein removal of the lenses is required. [0003] Removal of human lenses has been achieved by various surgical techniques in the past. The most prevalent technique at this time involves a process known as "phacoemulsification". This process involves the use of a handpiece with a tip that vibrates at an ultrasonic frequency. After making a small incision in the eye, the ophthalmic surgeon employs this handpiece to emulsify the lens within the capsular bag of the eye, and then employs the irrigation and aspiration modes of the handpiece to remove the lens particles from the capsular bag. Millions of cataract patients have had their cataractous lenses removed by means of the phacoemulsification procedure. Although ophthalmic surgeons have mastered the use of the phacoemulsification handpiece and associated surgical techniques, the use of an ultrasonic needle or tip within the eye presents inherent risks and concerns. Ophthalmic surgeons and others skilled in the art have therefore searched for improved devices and procedures for removing the human lens. [0004] A new lens removal procedure known as "liquefracture" is currently being developed by Alcon Research, Ltd. This procedure is described in U.S. Pat. No. 5,616,120 (Andrew, et al.), U.S. Pat. No. 5,885,243 (Capetan, et al.), U.S. Pat. No. 5,989,212 (Sussman, et al.), U.S. Pat. No. 5,997,499 (Sussman, et al.) and U.S. Pat. No. 6,080,128 (Sussman, et al.), the entire contents of the foregoing patents are hereby incorporated in the present specification by reference. [0005] Liquefracture is a new technique wherein the lens is disintegrated by applying hot pulses of a solution to the lens via an irrigation/aspiration handpiece. The handpiece, such as those described in the above-cited patents, includes a chamber for heating the solution and generating pulses of heated solution that are expelled from the handpiece. The lens is disintegrated by means of a combination of the heat absorbed from the solution and the force of the pulses of the solution impacting the lens tissue. The solution utilized for this purpose is referred to herein as the "liquefracture solution". [0006] Due to the delicacy of the intraocular tissues, both the extent to which the solution can be heated and the force or velocity of the pulses are necessarily constrained. In order to prevent damage to surrounding tissues, the stream of hot, pulsed solution is surrounded by a conventional irrigating solution which dissipates both the heat and force of the pulsed solution after it impacts the lens tissue. This second solution is referred to herein as either the "irrigating solution" or the "outer" or "dissipating" solution. [0007] Prior to the present invention, the solution utilized for both the liquefracture solution and the irrigating solution has been a conventional balanced salt solution such as BSS.RTM. (Balanced Salt Solution) Sterile Irrigating Solution, which is available from Alcon Laboratories, Inc., Fort Worth, Tex. Although this type of solution is generally adequate, there is a need for improved solutions which enhance the disintegration of the lens with the pulsed, heated solution and facilitate removal of the lens fragments following disintegration of the lens. The present invention is directed to filling this need. SUMMARY OF THE INVENTION [0008] The present invention is based on the discovery of a means for enhancing the effectiveness of the liquefracture solution in disintegrating the lens material during the above-described liquefracture procedure. More specifically, it has been discovered that the effectiveness of the liquefracture solution can be enhanced by increasing the pulse force of the solution. The effectiveness of the liquefracture solution can be further enhanced by including an agent which forms a temporarily insoluble precipitate at the temperatures utilized to form the hot, pulsed solution, thereby resulting in particles that act as abrasive agents. [0009] The pulse force of the liquefracture solution is increased by including a viscosity-enhancing agent in the solution used to form the hot, pulsed solution, thereby increasing the length of time for which the solution is retained in the heating/expansion chamber of the liquefracture handpiece and permitting more energy to be stored in the pulse of fluid. The pulse force can be further enhanced by including a small amount of a gas-generating propellant in the solution used to form the hot, pulsed solution, thereby increasing the velocity or force of the hot pulsed solution. [0010] In a preferred embodiment of the present invention, the effectiveness of the liquefracture procedure is further enhanced by including a viscosity-enhancing agent in the irrigating solution utilized as the outer or dissipating solution in the procedure. The enhanced viscosity of the irrigating solution increases the ability of the solution to dissipate the heat absorbed from the liquefracture solution. As a result, the temperature or proportion of the liquefracture solution can be increased (i.e., relative to the irrigating solution), thereby further enhancing the ability of the liquefracture solution to disintegrate the lens material. [0011] The increased pulse force of the solutions of the present invention enhances the effectiveness of the liquefracture procedure, relative to the speed at which the lens is disintegrated and the extent to which liquefracture can be utilized to remove relatively hard lenses. The inclusion of an abrasive agent in the solutions further enhances the effectiveness of the liquefracture solution by increasing the ability of the solutions to cut and disintegrate cataractous lens material. DETAILED DESCRIPTION OF THE INVENTION [0012] The improved liquefracture solutions of the present invention have been discovered as a result of a careful balancing of several factors. For example, the desired goal of enhancing the ability of the liquefracture solution to disintegrate the lens must be balanced against other required physical characteristics of the solution, such as the need for the solution to flow through the liquefracture handpiece and associated surgical equipment during the surgical procedure. [0013] The ability of a liquefracture solution to disintegrate a cataractous lens is directly dependent on the force of the pulsed solution as it impacts the lens tissue. This force is referred to herein as the "pulse force" of the liquefracture solution. As indicated above, it has been discovered that the pulse force of the liquefracture solution can be increased by enhancing the viscosity of the liquefracture solution. Enhancing the viscosity of the liquefracture solution increases the residence time of the solution in the heating chamber of the liquefracture handpiece, thereby increasing the energy absorbed by the solution and increasing the force by which the solution is expulsed from the chamber. [0014] Various types of agents may be utilized to enhance the viscosity of the liquefracture solution, such as chondroitin sulfate, sodium hyaluronate or other proteoglycans; cellulose derivatives, such as hydroxypropyl methylcellulose ("HPMC"), carboxy methylcellulose ("CMC"), and hydroxyethyl cellulose ("HEC"); collagen and modified collagens; galactomannans, such as guar gum, locust bean gum and tara gum, as well as polysaccharides derived from the foregoing natural gums and similar natural or synthetic gums containing mannose and/or galactose moieties as the main structural components (e.g., hydroxypropyl guar); xanthan gum; gellan gums; alginate; chitosans; polyvinyl alcohol; carboxyvinyl polymers (e.g., carbomers such as the Carbopol.TM. brand polymers available from B.F. Goodrich); and various other viscous or viscoelastomeric substances, including but not limited to those described in U.S. Pat. No. 5,409,904 (Hecht, et al.), the entire contents of which are hereby incorporated by reference in the present specification. [0015] The following patent publications may be referred to for further details concerning the above-listed viscosity-enhancing agents: U.S. Pat. No. 4,861,760 (gellan gums); U.S. Pat. No. 4,255,415 and WIPO Publication No. WO 94/10976 (polyvinyl alcohol); U.S. Pat. No. 4,271,143 (carboxyvinyl polymers); WIPO Publication No. WO 99/51273 (xanthan gum); and WIPO Publication No. WO 99/06023 (galactomannans). The entire contents of the foregoing references pertaining to the structures, chemical properties and physical properties of the respective viscosity enhancing agents described above are hereby incorporated in the present specification by reference. [0016] As demonstrated in Example 8 below, it has been found that the use of higher molecular weight fractions of polymeric materials as the viscosity enhancing agent is desirable, because the higher molecular weight fractions generally produce greater pulse forces than lower molecular weight fractions of the same material. The use of higher molecular weight fractions is therefore preferred. [0017] The most preferred viscosity-enhancing agent is HPMC at a molecular weight of 86,000 to 260,000. As discussed below, HPMC is also preferred as the transient abrasive agent of the improved liquefracture solutions described herein. [0018] The above-described viscosity-adjusting agents will be utilized in an amount sufficient to provide the liquefracture solutions of the present invention with an enhanced viscosity. As utilized herein, the phrase "enhanced viscosity" means a viscosity which is greater than the viscosity of aqueous humor and standard irrigating solutions, both of which generally have viscosities of approximately 1 centipoise ("cps"). The liquefracture solutions of the present invention will typically have viscosities of from greater than 1 cps to about 15 cps, preferably from about 2 to about 7 cps. [0019] The liquefracture solutions of the present invention contain one or more of the above-described viscosity enhancing agents in an ophthalmically acceptable vehicle. Various types of solutions may be utilized as a vehicle for the liquefracture solution; however, the conductivity of the liquefracture solution is a factor which must be taken into account relative to selection of an appropriate vehicle. [0020] Due to the very high resistance of water, which results in low conductivity, water does not heat up sufficiently and thus does not produce adequate pulse force for liquefracture procedures. Ionic solutions, such as balanced salt solution, have relatively lower resistance to electricity, and therefore have higher conductivity. This higher conductivity allows the ionic salt solutions to be heated sufficiently to be utilized in liquefracture. However, the conductivity of the solution has to be balanced with instrument design criteria, such as the need to avoid corrosion or other damage to the liquefracture handpiece and avoid clogging of the handpiece or other fluid channels in the ophthalmic surgical operating system. [0021] The liquefracture solutions are preferably formulated to be isotonic. The osmolality of the solution is an indirect measure of conductivity, since both properties are dependent on the ionic concentration. The liquefracture solutions of the present invention preferably have an osmolality of from about 200 to about 400 milliosmoles per kilogram of water (mOsm/kg"). Continue reading about Solution for removing cataracts via liquefracture... Full patent description for Solution for removing cataracts via liquefracture Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Solution for removing cataracts via liquefracture patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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