Surgery – Instruments – Corneal cutter or guide for corneal cutter
Reexamination Certificate
2000-03-20
2001-11-06
Recla, Henry J. (Department: 3731)
Surgery
Instruments
Corneal cutter or guide for corneal cutter
Reexamination Certificate
active
06312440
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to fluid jet surgical devices, and more particularly to fluid jet devices used for refractive surgery.
In recent years the use of surgical techniques for correction of ophthalmic refractive malfunction has progressed from experimental laboratory operations to widely accepted, commonplace procedures. Radial keratotomy (RK), photorefractive keratotomy (PRK), and myopic keratomileusis (MKM) have all become routine techniques in ophthalmology. Such aggressive surgical treatment is a relatively new development in ophthalmology. However, many patients require good uncorrected visual acuity for various occupations, such as pilots or professional athletes, and other patients seek good uncorrected visual acuity for cosmetic or psychological reasons. Moreover, some patients have subnormal vision, even when optimally corrected with spectacles or contact lenses, and seek surgical correction for improved vision.
Some photorefractive surgical techniques involve a lamellar keratotomy, in which a hinged flap of apical corneal tissue is created by incision in the cornea generally perpendicular to the primary visual axis. A second cut is then made, in which a thin wafer of stroma is removed. The flap is then returned to its initial position and permitted to heal in place. Removal of the thin wafer of stroma alters the conformation of the corneal apex, thereby modifying the refractive characteristics of the cornea. Clearly, the placement and formation of the second cut, as well as the thickness and planarity of the first incision, are crucial to the success of this technique.
Lamellar keratotomy has been performed using a microkeratome device, in which a high speed oscillating head supports a blade that creates the corneal cuts. However, the blade thickness, as well as the mechanical vibration and motion of the moving cutter limits the fineness and planarity of the incision, which in turn limits the potential for successful outcome of the surgery.
The use of surgical lasers has been approved by the U.S. FDA for carrying our lamellar keratotomy, in a procedure known by the acronym LASIK. A laser beam cuts tissue by forming a very narrow beam of light, and sweeping the beam through the corneal tissue. The energy density within the beam is sufficient to vaporize any cellular structure in its path, and the mechanism of the laser cutting process is essentially thermal pyrolysis. There is the opportunity for byproducts of tissue heating and burning to be formed in the process, and these byproducts can adversely affect the healing process of the surgical wound.
Recently, a high speed water jet has been used in lamellar keratotomy, in a technique termed hydrorefractive keratoplasty (HRK). A water jet having a diameter less than 50 &mgr;m is used to form the corneal incisions. The water jet is far smaller in diameter than the thickness of a cutting blade, whereby the incisions may be much finer, resulting in less tissue trauma, better healing, and greater potential for success. Also, the water jet cuts, delaminates, and separates tissue by imparting very high kinetic energy; unlike laser cutting, there is no formation of byproducts of tissue oxidation and burning.
The water jet is a linear “beam” which must be swept through the corneal tissue to effect the necessary incisions. The mechanism to effect the beam movement consists generally of a track on which the water jet nozzle is mounted in slidable fashion. The prior art demonstrates a need for an improved mechanism for guiding a water jet cutting beam with greater resolution and control, and for controlling the thickness of the cut and the thickness and conformation of the stromal wafer.
SUMMARY OF THE INVENTION
The present invention generally comprises an apparatus for supporting and guiding the movement of a high speed liquid jet used for cutting, particularly in the formation of ophthalmic incisions. A salient feature of the apparatus is that it eliminates the mechanical free play of prior art sliding or rolling devices, thereby taking full advantage of the extremely fine cutting beam produced by a high pressure cutting jet, and forming incisions of unprecedented planarity and thinness.
The apparatus includes an instrument body, comprised of an elongated rectangular portion and a tapered end portion extending distally therefrom. A cylindrical housing is secured to the tapered end, and is provided with a stepped opening extending axially therethrough. A bottom surface of the rectangular portion is provided with a pair of channels extending laterally in parallel, spaced apart configuration, and a pair of high precision crossed roller slides is secured in the pair of channels. Within the rectangular body portion, a micro-motor assembly is secured, including a shaft encoder, a gear box, and a pinion gear secured to the output of the gear box and extending generally between the crossed roller slides.
A liquid jet carrier includes a longitudinally extending body having a pair of channels extending laterally therein to receive the crossed roller slides in slidably translating fashion. A drive slot extends parallel to one of the crossed roller slides, and is disposed to receive the pinion gear of the micro-motor assembly. A rack gear also extends into the drive slot, and is engaged by the pinion gear to drive the jet carrier in lateral translation riding on the crossed roller slides. The jet carrier includes a proximal connector for a high pressure fluid hose, and a jet nozzle assembly extending from the distal end of the carrier. The encoder enables high precision movement and positioning of the jet carrier in the lateral direction.
The apparatus includes a plurality of guide members, all having common structural features adapted to engage the stepped opening of the distal end of the instrument body. Each guide member includes a generally cylindrical body, and the central portion comprises a reticle and applanation plate, both formed integrally of transparent plastic, so that the surgical site may be visualized directly therethrough. Differing guide members are provided with applanation plates of various thicknesses. The cylindrical body also includes an annular vacuum suction ring having a smoothly beveled annular opening disposed to impinge on an annular zone of the eye surrounding the cornea. The suction ring is connected to a vacuum source to selectively secure the device on the eye and establish a fixed position with respect thereto.
The guide member further includes a jet slot extending in the sidewall thereof perpendicular to the axis of the cylindrical housing. The slot subtends an angle less than 180°, and is disposed to receive the distal end of the jet nozzle assembly with minimum clearance for lateral translation in a chordal path. An aspiration groove is formed within the guide member in diametrical opposition to the slot to aspirate and remove the liquid and tissue debris generated by the liquid jet. The aspiration groove is also connected to a vacuum aspiration source.
To use the apparatus of the invention, a guide member having the desired applanation characteristics and thickness is selected and installed in the stepped opening of the instrument. The guide members and the stepped opening are provided with quick connect, self-aligning features that assure rapid installation at the proper angular orientation. The apparatus is properly position by visual inspection, using the reticle of the guide member, and the suction ring is connected to a vacuum source to secure the apparatus at the selected position on the eye. Thereafter, the jet nozzle is translated to a start position, and high pressure fluid is delivered to the jet nozzle to form a high velocity jet beam of vary narrow diameter. The micro-motor assembly is actuated concurrently with the jet to translate the jet laterally through a portion of the corneal stroma and form a planar incision therein that defines a corneal apical flap. This process is then repeated to form a second incision at a second plane, defining a wafer of co
Doherty Rex E.
Hood Larry L.
Hood William T.
Bui Vy Q.
Recla Henry J.
SurgiJet, Inc.
Zimmerman Harris
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