Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Eye prosthesis
Reexamination Certificate
2000-02-22
2002-03-19
Nguyen, Dinh X. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Eye prosthesis
C128S898000
Reexamination Certificate
active
06358279
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a mini capsulorhexis valve device comprising a flexible discoid flap-valve member attached to a flexible retainer member, the device serving to seal a capsulorhexis opening created during ocular interventions.
2. Description of the Related Art
The human eye, as depicted in
FIG. 5
, comprises a roughly spherical organ having essentially three distinct layers of tissue, divided into three basic chambers. The tough outer sclerotic coat
120
serves as a protective barrier for the eye, and forms the transparent cornea
122
through which light passes into the eye. The sclerotic coat
120
is composed of dense collagenous tissue. The middle choroid coat
124
forms the iris
126
, a diaphragm that controls the amount of light admitted into the interior of the eye through the pupil. Immediately posterior to the iris
126
is the transparent crystalline lens
128
, held in place by zonular fibers attached to ciliary processes surrounding the crystalline lens
128
. The zonular fibers collectively culminate in the suspensory ligament of the lens. The region between the cornea
122
and crystalline lens
128
is denoted the anterior chamber
130
of the eye, whereas the gap created between portions of the crystalline lens
128
and iris
126
is known as the posterior chamber
132
. Ciliary processes generate aqueous humor, which fills the anterior chamber
130
and posterior chamber
132
. Aqueous humor provides for nutrient and metabolic exchange between the avascular cornea
122
, crystalline lens
128
, and iris
126
. The posterior pole of the crystalline lens
128
abuts the hyaloid fossa of the posterior vitreous chamber
134
of the eye. Accommodation, the process of changing the focus of the eye between near and distant objects, is achieved by constriction and relaxation of the ciliary muscle
136
connected to the crystalline lens
128
via the zonular ligament. Such movement by the ciliary muscle
136
serves to shape the crystalline lens
128
to the appropriate optical configuration for focussing light rays from these objects onto the inner coat of the eye, structurally known as the retina
138
.
The crystalline lens is a biconvex body, having an anterior convexity less steep and of a greater radius of curvature than its more parabolic posterior convexity. The lens is composed of elongated, prismatic cells known as lens fibers, which are tightly packed to form lamellar structures. Intracellular granular crystallins within the lens fibers confer upon the lens its transparent and refractive characteristics. Lens fiber structure and composition varies within the lens such that a firm central nucleus may be distinguished from a softer surrounding cortex. The entire lens is encompassed by the lens capsule (capsula lentis), a basement membrane into which the zonular fibers are inserted. The elastic lens capsule is composed of collagen fibers, glycosaminoglycans and glycoproteins. Due to its elastic properties, the lens capsule can stretch substantially in circumference without tearing.
A variety of disorders are known to impair or destroy normal function of the eye, including disorders of the lens, such as cataracts and presbyopia. Cataracts arise from progressive clouding of the crystalline lens, which, if left untreated, eventually obscures light rays from focussing on the retina. Historically, cataracts were surgically treated by either intracapsular removal of the entire lens structure, including the outer lens capsule and the inner crystalline lens matter, or extracapsular removal of the central portion of the anterior capsule and the crystalline lens matter, leaving in place the posterior lens capsule, known in the art as the ECCE procedure. These procedures are prone to complications, such as retinal detachment, and, in the case of extracapsular cataract extraction, opacification of the posterior capsule.
Recently developed lens refilling procedures may reduce the incidence of many complications associated with traditional cataract treatment modalities. One such procedure is disclosed in U.S. Pat. No. 4,002,169, in which a rotary masticating tool is introduced into the lens structure via an inserted hollow needle. The capsular tissue contents, including the cataract, lens cortex and lens nucleus, are physically liquefied and then withdrawn from the lens capsule via suction through the needle. Such a process leaves the lens capsule intact as a capsular bag within the posterior chamber. Often, a chemical treatment or sonication (phacoemulsification) is preferred over physical mastication for liquefying the lens. Following suction removal of the liquefied crystalline lens, the capsular bag may be flushed to remove remaining debris and then refilled with a molded synthetic lens, as disclosed in U.S. Pat. No. 5,674,282.
Alternatively, a new lens may be created in situ with a filler material having the appropriate characteristics to mimic the function of the natural crystalline lens. Many ophthalmic procedures designed to restore accommodation of the eye, such as lens refilling procedures for the correction of presbyopia and cataracts, rely on the replacement of endogenous lens matrix material with a transparent material of similar consistency and index of refraction and spectra.
Some of the preferred materials for filling the capsular bag comprise UV-curable polymers that require exposure to ultraviolet light to induce crosslinking. Such crosslinking typically requires two openings be created in the wall of the eye via bimanual surgery, which occupies both hands of the ophthalmic surgeon. Alternatively, crosslinking may be effected through the cornea, but such procedures may damage corneal tissues.
Intraocular lenses may comprise relatively hard materials, relatively soft materials, or a combination of both types of materials. For example, methyl methacrylates, polysulfones or other relatively hard, biologically inert optical materials may be used alone, or in combination with softer biologically inert silicones, hydrogels or semi-rigid thermolabile materials.
U.S. Pat. No. 5,391,590 discloses compositions useful as injectable intraocular lens material. Examples of polymerizable formulations include one or more polyorganosiloxanes having a vinyl functionality, a silicon-bonded hydride group, and the like. Such compositions may comprise soft, fast curing, low temperature vulcanization silicone gels capable of in situ polymerization within the capsular bag. High molecular weight, high viscosity silicone precursor fluids are preferred, as they are less likely to leak from the injection site prior to polymerization. Such high viscosity materials only require a low cross-linking density to achieve an elastic modulus similar to a human crystalline lens. However, a reduced cross-linking density of these polymers results in an unacceptable gummy product having low resilience.
Certain low viscosity, low molecular weight fluids have desirable properties upon cure for injectable ocular lenses, but readily leak from the injection site. Upon curing of leaked gel, a bump may form on the surface of a refilled capsule. Such bumps are known to irritate the iris and mediate corneal edema. In an attempt to overcome this limitation, suitable low molecular weight fluids may be pre-cured to induce polymerization prior to injection in to the lens capsular bag. Injection of such partially polymerized materials through a cannula may cause shear stress, which results in rough areas of the polymerized material that impair the function of the synthetic lens. Additionally, pre-cured polymer materials typically must be injected shortly after initiating crosslinking to prevent over-curing and reduced flow through the cannula, making such materials awkward to use.
Typically, the capsular bag tends to under fill unless very high density materials, such as gels having a viscosity of greater than 4 Mcts, are used. As mentioned hereinabove, viscous liquids and gels introduced into the capsular bag for this purpose often leak from th
Chapon Pascal
Parel Jean-Marie
Tahi Hassan
Nguyen Dinh X.
University of Miami
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