Surgery – Instruments – Light application
Reexamination Certificate
2000-12-28
2003-02-18
Look, Edward K. (Department: 3745)
Surgery
Instruments
Light application
C606S006000, C604S043000
Reexamination Certificate
active
06520955
ABSTRACT:
TECHNICAL FIELD
The present invention relates to photodynamic therapy for treatment of ocular disease in general. More specifically to the use of refractive polymers in the treatment of cataracts.
BACKGROUND ART
Previously, the primary approach to cataract removal has focused primarily on the use of tissue ablation employing ultrasonic or laser energy. Cataracts removed by this extracapsular method require extraction of the anterior capsule and lens substance but leave intact the posterior capsule of the lens. Extracapsular surgical techniques are usually performed by technologies that rely on high-impact energy pulses to shatter the lens into fractions that must be constantly degraded further before they may be removed by aspiration. The process of lens fractionalization and removal demands a high level of skill which is tedious and time consuming.
Lens proteins and their constituent amino acids have been studied to determine their behavior in response to radiation. Although most of the amino acids of which proteins are comprised do not absorb ultraviolet light (of a wavelength greater than 220 nm) tryptophan, and to a lessor phenylalanine and tyrosine, are known to absorb significant amounts of ultraviolet light and as a result to be susceptible to structural degradation a process herein referred as “phacophotolysis”. Tryptophan photodegradation may, for example, be induced through irradiation at wavelengths between 240-310 nm, and the efficiency of photodegradation is influenced by a number of factors including pH, temperature and encapsulation of photodynamic components in liposomes. Liposomal preparations are particularly useful where the photosensitizing agent is a green porphyrin since it has a particular affinity for lipoproteins. Additional components including monoclonal antibodies, receptor ligands and cytotoxins can be combined with photosensitizing agents to enhance selectivity to lens tissue and efficacy of photodegradation. Although tryptophan is the least common amino acid of human proteins it is the most photolabile of amino acids and present in high concentrations in human lens tissue.
Porphyrin-type photosensitizers used in photodynamic therapy, either used singly or in conjunction with a hydrophilic polymer, can be administered into the intralenticular space to enhance degradation of lens tissue (phacophotolysis). The photosensitive agents and their various formulations are generally known in the art.
Modern lasers are capable of producing picosend (10-12 second)bursts of extremely high intensity. In a picosecond pulse the photon intensity is quite high. Photosensitive chemicals in lens tissue can be actuated by lasers of variable power and wavelength. Hence, degradation of lens tissue by phacophotolysis provides a novel and unique method of cataract removal not heretofore practiced by prior art.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention however, the following U.S. patents were considered related:
U.S. Pat. No.
Inventor
Issue Date
4,078,564
Spina
3/1978
4,608,050
Wright
8/1986
4,919,151
Grubbs, et al
4/1990
5,022,413
Spina, Jr. et al
6/1991
5,095,030
Levy, et al
3/1992
5,957,914
Cook, et al
9/1999
The U.S. Pat. No. 4,078,564 issued to Spina discloses an enzymatic intralenticular cataract treatment for removal of nuclear cortical and subcapsular regions of the cataractous lens through enzymatic digestion thereof The treatment comprises introduction of a concentrated solution of mixed exogenous enzymes into the nuclear and cortical regions of a cataractous lens, and after enzymatic digestion removing the liquefied cataractous material. The procedure allows removal of the nuclear, cortical and subcapsular portions of a cataractous lens through a very tiny incision in the eye and lens capsule, leaving all other structures within the eye intact.
The U.S. Pat. No. 4,608,050 issued to Wright discloses a method of treating defective lenses in the eye, wherein the natural lens is removed leaving the lens capsule intact. A curable liquid composition comprising a crosslinkable siloxane polymer, a crosslinker and a crosslinking catalyst is injected into the lens capsule where the composition cures at body temperature to a solid, transparent synthetic lens which remains clear in the presence of physiological fluids.
The U.S. Pat. No. 4,919,151 issued to Grubbs, et al discloses a synthetic polymer for endocapsular lens replacement in an eye. The polymer, which is injected into the lens capsule after removal of the lens, comprises an oxygen-stabilized photosensitive prepolymer. An example of such a prepolymer comprises polyether with urethane linkages with one or both ends capped with a functional group containing at least one double bond, such as an acrylate, a methacrylate, or a styrene. The polymerization reaction is initiated with a photoinitiator such as dimethoxyphenylacetophenone and is quenched in the presence of oxygen. Contrary to the prior art polymers, the time of curing is approximately one minute. The viscosity and thickness of the polymer formed may be tailored to achieve a desired index of refraction of between about 1.3 and 1.6.
The U.S. Pat. No. 5,022,413 issued to Spina, Jr. et al discloses a method for treating cataracts by introducing a lenticular tissue dispersing agent into the opacified lens through a small opening in the lens capsule so that the capsule remains substantially intact. The tissue dispersing agent is contained in the lens by a gel-forming substance which functions to block the opening in the lens capsule, preventing its escape. This treatment is preferably carried out in conjunction with laser induced phacofracture.
The U.S. Pat. No. 5,095,030 issued to Levy, et al discloses a group of hydro-monobenzoporphyrins “green porphyrins” (Gp) having absorption maxima in the range of 670-780 nanometers, which are useful in treating disorders or conditions which are subject to hematoporphyrin derivative (HPD) treatment in the presence of light, or in treating virus, cells and tissues generally to destroy unwanted targets. The use of the Gp permits the irradiation to use wavelengths other than those absorbed by blood. The Gp may also be conjugated to ligands specific for receptor or to specific immunoglobulins or fragments thereof to target specific tissues or cells for the radiation treatment. Use of these materials permits lower levels of drug to be used, thus preventing side reactions which might destroy normal tissues.
The U.S. Pat. No. 5,957,914 issued to Cook, et al discloses a laser photo-optic breakdown probe and handpiece system especially suited for small-incision cataract removal including an optical fiber through which a pulsed source of laser energy is delivered to a target spaced from the distal end of the fiber. The fiber is routed through a first guide tube with the target mounted at an angle on the end thereof. Holes are provided in the guide tube for the flow of infusion fluid therethrough. A second aspiration tube surrounds and provides rigidity to the guide tube, shields the distal end of the fiber and target, and serves as a channel for aspirated fluids and dislodged cataractous material. The guide tube is affixed to a transfer housing to which infusion and aspiration connections are made. The aspiration tube forms part of a handle assembly which is detachably coupled to the transfer housing.
For background purposes and as indicative of the art to which the invention relates, reference may be made to the following remaining patents found in the search:
U.S. Pat. No.
Inventor
Issue Date
4,135,516
Spina
1/1979
4,192,685
Horike et al.
3/1980
4,388,483
Finkelmann et al.
6/1983
4,395,806
Wonder et al
8/1983
4,440,570
Kreuzer et al.
10/1983
4,573,998
Mazzocco
3/1986
4,846,172
Berlin
7/1989
4,880,512
Cornelius et al.
11/1989
5,257,970
Dougherty
11/1993
5,298,018
Narsisco Jr.
3/1994
5,313,320
Kornfield et al.
5/1994
5,469,867
Schmidtt
11/1995
5,476,514
Cumming
12/1995
5,514,669
Selman
5/1996
5,705,518
Richter et al.
1/1998
5,738,667
Cota Albert O.
Look Edward K.
White Dwayne J.
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