1. Field of the Invention:
This invention relates generally to ophthalmic instruments and more particularly to a novel ophthalmic lens insertion instrument and to an ophthalmic lens insertion kit and lens insertion package embodying the instrument for use in implanting a foldable intraocular lens in a patient""s eye.
2. Discussion of the Prior Art:
The human eye is subject to a variety of abnormal conditions that degrade or totally destroy proper optical functioning of the eye. One of the more common of these conditions is a cataract which clouds the natural crystalline lens and obstructs or blocks passage of light rays through the lens to the retina. The ophthalmic procedure for curing a cataract involves extraction of the cataractous natural lens matrix through an incision in the cornea of the eye and implantation of an artificial intraocular lens in the eye through the incision.
In the early days of cataract surgery, the entire cataractous natural lens was removed by a surgical procedure known as intra-capsular lens extraction. While this procedure is occasionally used today in certain circumstances, it has many disadvantages, among the more serious of which is the need to make a relatively large incision in the eye to permit removal of the natural lens through the incision the risks associated with such a large incision.
These disadvantages of intra-capsular lens extraction led to the development in the 1970""s of an improved procedure for removing a cataractous natural lens. This improved procedure, known as extra-capsular extraction, involves removal of a central portion or all of the anterior capsule of the natural lens, phacoemulsification of the cataractous natural lens matrix, and aspiration of the emulsified matrix through the resulting anterior capsule opening and a corneal incision. Such extra-capsular extraction with phacoemulsification requires only a relatively small corneal incision on the order of 3 mm in length and thereby greatly reduces or eliminates many of the risks associated with intra-capsular lens extraction.
It was not until the development of the foldable intraocular lens in 1986, however, that this small incision advantage of extra-capsular lens extraction with phacoemulsification could be utilized. This was due to the fact that up until 1986, the only available intraocular lenses were hard lenses which required corneal incisions on the order of 6-8 mm in length for lens insertion. Accordingly, even though the natural lens could be extracted through a 3 mm corneal incision, insertion of a hard intraocular lens into the eye through the incision necessitated enlargement of the incision to 6-8 mm. A foldable intraocular lens, on the other hand, is foldable to a compact folded configuration in which the folded lens is capable of insertion through a 3 mm corneal incision. Accordingly, the development of the foldable intraocular lens enabled extra-capsular extraction of a cataractous natural lens from and implantation of an artificial intraocular lens in a patient""s eye through a 3 mm corneal incision in the eye.
A foldable intraocular lens has a normal unfolded lens configuration in which the lens is conditioned to perform its optical lens function in the eye. The lens is foldable to a compact folded configuration for insertion into the eye through a small corneal incision, such as the 3 mm incision required by extra capsular lens extraction with phacoemulsification. In its folded configuration, the lens stores elastic strain energy which unfolds the lens to its normal lens configuration when released within the eye.
A variety of foldable intraocular lenses and instruments for inserting such lenses into the eye have been developed. Among the patents disclosing such lenses and instruments are the following:
U.S. Pat. No. 4,573,998 dated Mar. 4, 1986, to Mazzocco; U.S. Pat. No. 4,681,102 dated Jul. 21, 1987, to Bartell; U.S. Pat. No. 4,715,373 dated Dec. 29, 1987, to Mazzocco et al; U.S. Pat. No. 4,763,650 dated Aug. 16, 1988, to Hauser; U.S. Pat. No. 4,765,329 dated Aug. 23, 1988, to Cumming; U.S. Pat. No. 4,834,094 dated May 30, 1989, to Patton et al; U.S. Pat. No. 4,862,885 dated Sep. 5, 1989, to Cumming; U.S. Pat. No. 4,934,363 dated Jun. 19, 1990, to Smith; U.S. Pat. No. 4,976,716 dated Dec. 11, 1990, to Cumming; Japanese U.S. Pat. No. 5-103,808 dated Apr. 27, 1993, to Kikuchi.
Another lens insertion device for inserting a foldable intraocular lens into a patient""s eye is currently being marketed by a company named IOVISION. This IOVISION instrument comprises a lens holder and a ram permanently joined by a flexible strap. The lens holder includes tubular portion having a slender front tip for insertion into a patient""s eye, a bore extending axially through the tubular portion and containing a plunger movable through the bore, and a lateral lens storage chamber having an inner end opening laterally to the bore and an open outer end. The chamber is disposed in a plane parallel to and laterally offset from the longitudinal axis of the bore and opens at its inner end laterally into the bore through a wall opening in the bore whose width circumferentially of the bore approximates one quarter the bore circumference. The ram has a laterally facing concave inner end face of approximately this same quarter circumferential width and the same radius of curvature as the bore.
In use, the IOVISION instrument and unfolded lens are stored separately in a sterile condition until needed and are transported separately to the operating room. Within the operating room, the unfolded lens and ram are inserted, lens first, into the lens storage chamber of the instrument through the open outer end of its chamber. The ram is then pressed inwardly through the chamber to force the lens into the bore within the instrument tubular portion. The arcuate inner end face of the ram coacts with the curved wall of the bore to fold or curl the lens to its folded configuration within the bore. The slender tip of the tubular portion is then inserted into the patient""s eye through a corneal incision in the eye after which the instrument plunger is moved forwardly through the tubular portion to eject the folded lens from the tubular portion into the eye. The folded lens stores elastic strain energy which unfolds the lens within the eye.
The invention provides an improved ophthalmic lens insertion instrument for inserting a foldable intraocular lens in its compact folded configuration into a patient""s eye. The invention also provides an ophthalmic lens insertion kit and lens insertion package each including both the improved instrument and a foldable intraocular lens stored in a sterile condition in its normal unfolded configuration with the instrument in total readiness for insertion of the lens into a patient""s eye.
The improved ophthalmic instrument of this invention includes a lens insertion assembly and a lens insertion actuator. The lens insertion assembly includes a housing having an elongate tubular portion and a lens storage chamber extending laterally of the tubular portion for storing a foldable intraocular lens in its normal unfolded configuration. The tubular portion contains an axial bore and has a slender front tip for insertion into a patient""s eye. The lens storage chamber has an inner end opening laterally into the bore through an opening in the wall of the bore and normally contains lens transfer and folding means for moving the lens into and folding the lens to its compact folded configuration within the bore. The bore contains lens insertion means for ejecting the folded lens from the bore into the patient""s eye.
In the preferred embodiments of the invention, the lens transfer and folding means comprises a ram movable between an outer retracted position at the outer end of the lens storage chamber and an inner extended position at the inner end of the chamber. In its outward retracted position, the ram forms with the chamber a lens storage space within the inner end of the chamber. In the inner extended position of the ram, its inner end extends into the wall opening of the bore with the inner end face of the ram substantially flush with and conforming to the curvature of the surrounding wall of the bore. The lens insertion means comprises a plunger movable through the housing bore, and an end extending rearwardly from the tubular portion. The insertion actuator of the instrument is mounted on the tubular portion and is operable to move the plunger of the insertion assembly forwardly through the bore in the tubular portion.
The lens insertion assembly is designed to store for a prolonged period of time a foldable intraocular lens in its normal unfolded configuration in a storage position within the lens storage space of the lens storage chamber with the assembly ram located in its outwards retracted position in the chamber. Inward movement of the ram to its inward extended position in the chamber pushes the unfolded lens inwardly into the bore of the housing tubular portion and then curls or folds the lens to its folded configuration within the bore with the folded lens situated in a pre-insertion position within the bore. The assembly plunger is then moved forwardly through the bore to eject the folded lens from the insertion assembly through the tip of its tubular portion.
A feature of the presently preferred inventive embodiments resides in the fact that the lens storage chamber and ram of the insertion assembly have a common longitudinal medial plane containing the longitudinal axis of the tubular portion bore so that the bore is laterally centered relative to the chamber and ram. The wall opening between the bore and chamber and the inner end face of the ram are bisected circumferentially by this medial plane and have circumferential widths approximating one-half the circumference of the bore. This feature assures optimum folding or curling of the lens to its folded configuration by inward movement of the ram.
A unique and important advantage of the present lens insertion instrument resides in its ability to store the lens for a prolonged period of time in its normal unfolded configuration directly within the lens insertion assembly with the ram positioned in its outwards retracted position in the lens storage chamber. The lens is thus stored in total readiness for insertion of the lens into a patient""s eye without the necessity of inserting the lens and ram into the chamber in the operating room as required in the IOVISION instrument described earlier. The insertion assembly and its stored unfolded lens together form a lens insertion kit which can be stored in a sterile condition, with or without the insertion actuator, as desired, depending on whether the actuator is permanently attached to or removable from the assembly. According to a feature of the invention, this lens insertion kit can be removably housed in an instrument holder contained within a sealed sterile pouch. The pouch, holder, and lens insertion kit together form a sterile lens insertion package which can be stored until needed. The instrument holder includes loading means for operating the insertion assembly ram to move the lens into and fold the lens within the bore of the assembly housing prior to removal of the assembly from the holder.