Surgery – Instruments – Means for removing – inserting or aiding in the removal or...
Reexamination Certificate
2000-11-28
2003-10-07
Vanatta, A. (Department: 3765)
Surgery
Instruments
Means for removing, inserting or aiding in the removal or...
C606S166000, C606S170000
Reexamination Certificate
active
06629980
ABSTRACT:
TECHNICAL FIELD
This invention relates to an instrument and method for creating an incision in an intraocular tissue, such as the anterior capsule of the eye.
BACKGROUND ART
An individual's vision involves the eye forming an image of an object and sending that image to the sensory centers of the brain. An object will reflect light through the cornea, the aqueous humor, the pupil, the lens, and the vitreous humor of the eye, wherein the reflective light is focused by the lens onto the retina (see FIG.
1
). The nerve fibers within the retina collectively leave the eye in the optic nerve and enter the brain where the visual signals are processed.
Among other factors, therefore, the quality of vision depends upon the transparency of the lens. An opacity of the lens, commonly known as cataract, may prevent a clear image from forming on the retina. The lens is encapsulated by a cellophane-like membrane covering its anterior and posterior surfaces, wherein the capsule is retained in position chiefly by suspensory ligaments termed zonules. Cataracts may be age-related, congenital or result from trauma, disease or medications, and are generally treated by performing extracapsular cataract extraction. In this procedure, an opening is provided in the anterior lens capsule through which instrumentation can enter and the opaque lens is removed and replaced by an artificial intraocular lens.
Each year, approximately 1.3 million cataract surgeries are performed in the United States, and several methods have been utilized for opening the anterior lens capsule to gain access to the lens nucleus and cortical material. Currently, the two most popular techniques for anterior capsulotomy are the “can-opener” technique and capsulorrhexis. In can-opener capsulotomy, a cystotome, knife, or needle is inserted through a small incision in the sclera or peripheral cornea and small connecting tears are made in the anterior lens capsule in a circular pattern. When a complete circle has been made by connecting the tears, a circular piece of the anterior capsule is then grasped with forceps and torn away along the perforations. Unfortunately, when opening the capsule with numerous small capsular tears, the small tags which remain become a focal area of least resistance and can lead to tears which extend radially and posteriorly to the posterior capsule. The detrimental result is a loss of structural stability of the capsule and an increased likelihood of vitreous entry into the anterior chamber.
Capsulorrhexis denotes a circular central opening in the anterior capsule. This continuous opening eliminates the residual tags common with the can-opener technique described above. In capsulorrhexis, a capsular incision is made with a cystotome, and this incision is coaxed to form a circular shape by pushing the leading edge of the freshly tearing capsule with the cystotome in a non-cutting fashion or by grasping the leading edge with forceps. This procedure is quite difficult to control by the surgeon. The tearing motion can lead to an undesirable tear toward the equator and the posterior capsule, and the opening size is hard to control. As such, capsulorrhexis requires a significant amount of skill, experience, and learning time to consistently obtain successful results.
As described above, opening the anterior capsule via an anterior capsulotomy is a very delicate procedure and is widely considered to be one of the most difficult steps in a cataract surgery. A poorly performed anterior capsulotomy significantly increases the difficulty in performing the subsequent surgical steps and the probability of operative complications. Complications resulting from a poor capsulotomy include zonular stress with subsequent breakage of the posterior capsule, vitreous loss, and large capsular tags preventing efficient lens removal. A poor capsulotomy also prevents placement of an intraocular lens in the capsular bag due to ill-defined capsular structures. Such complications are unfortunately frequent. An unsuccessful capsulotomy increases the risk of intraoperative complications such as vitreous loss and inability to implant a posterior chamber intraocular lens. The operative time and patient discomfort are increased, along with the risk of postoperative complications with decreased final best-corrected visual acuity results.
Furthermore, with either of the above-described techniques for anterior capsulotomy, the capsular opening's size or position is often not ideal. The location, size, and configuration of the incision have important consequences. For example, a small capsular opening can impair the safe removal of the lens nucleus and cortex and prevent proper intraocular lens insertion into the lens capsule. In addition, the excessive stress placed on the lens capsule which result from having to work with a small or eccentric capsular opening puts the eye at risk for zonular and capsular breakage.
Certain devices have been proposed to overcome the problems associated with conventional anterior capsulotomy techniques. For example, U.S. Pat. No. 4,766,897 issued to Smirmaul, and U.S. Pat. Nos. 5,269,787 and 5,873,883 issued to Cozean Jr. et al. each disclose instruments which include circular cutting members for incising the anterior capsule. However, use of such devices in small incision cataract surgery is limited due to their size. More particularly, the anterior lens capsule of the eye is shielded by the cornea and sclera, such that a passage wound must be cut in the corneal or scleral tissue before any surgical apparatus can reach the anterior capsule. It is desirable to have the width of the passage wound cut on the tissue as small as possible, preferably on the order of 2.4 to 2.7 mm in width. A small wound decreases the necessary surgical closing procedures, promote rapid healing, minimizes astigmatism, reduces potential infections, and offers rapid visual rehabilitation. Therefore, the instrumentation employed in cataract surgery should be capable of passing through a small wound.
In an attempt to meet this size requirement, alternative surgical devices have been proposed. For example, U.S. Pat. No. 5,135,530 issued to Lehmer discloses a deformable circular cutting ring which is provided between the two forward positions of two elongated arms. The arms crisscross each other and are hinged together, such that when the rearward portions of the two arms are squeezed toward each other, the forward positions of the two arms will move toward each other to compress the deformable circular cutting ring into a narrow elliptical shape. The overall width of the narrow elliptical shaped deformable circular cutting ring and the forward portions of the two elongated arms is small enough to be inserted into the anterior chamber of the eye through a small tissue wound of about 4 mm in width.
Similarly, U.S. Pat. No. 5,728,117 issued to Lash discloses a capsulorrhexis instrument that includes a flexible band having a cutting edge. The band is fixed to a plunger, and is retractable within a tube and extendable into a position projecting out of the tube. While in its retracted position within the tube, the band assumes a narrow elliptical shape. However, when the flexible band is in its extended position outside of the tube, such as inside the eye, it deforms into a circular shape for incising intraocular tissue.
While these deformable devices provide one solution to the size constraint imposed by a small tissue wound, the devices suffer from the disadvantages of being overly complex as well as costly to manufacture and maintain. Therefore, a need exists for an improved instrument and method for creating an intraocular incision within the constraints of small incision cataract surgery.
DISCLOSURE OF INVENTION
Therefore, it is an object according to the present invention to provide an instrument and method for incising an intraocular tissue which is capable of creating an incision of suitable size for lens removal, yet which requires only a small entry wound cut on the corneal or scleral tissue.
It is another object accordi
Brooks & Kushman P.C.
The Regents of the University of Michigan
Vanatta A.
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