Surgery – Instruments – Corneal cutter or guide for corneal cutter
Reexamination Certificate
2000-06-02
2003-07-29
Willse, David H. (Department: 3738)
Surgery
Instruments
Corneal cutter or guide for corneal cutter
Reexamination Certificate
active
06599305
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to the general field of ophthalmologic surgery, and in particular to surgical methods and devices for corneal implantation of optical lenses.
BACKGROUND
Numerous ophthalmic surgical procedures have been developed for correcting imperfect visual acuity such as myopia or hyperopia. A variety of keratomes have been developed over recent decades, devices for performing corneal resectioning to permit access to inner portions of the cornea, where surgical reshaping may then be used to permanently correct vision defects.
Referring to
FIGS. 1 and 2
a
, a typical prior art resectioning operation will separate flap
6
of corneal (and epithelial) tissue
2
from eyeball
4
. The outer layers of cornea and epithelial cells are separated and lifted away to expose the inner layers
12
of cornea
2
, and are left attached only as flap
6
. Exposed interior layers
12
of cornea
2
will to some extent adjust themselves, or their shape may be altered through further surgical steps, such as laser ablation or subsequent resectioning, to remove a contoured layer of corneal tissue. At the conclusion of the surgical procedure, flap
6
is typically replaced over inner corneal tissues
12
to protect the healing tissues.
However, most such surgical reshaping is not reversible, resulting in some risk of creating permanent visual aberrations for the patient. A known alternative is to surgically prepare an opening in the cornea of an eye having visual abnormalities, and to insert a lens therein. Such surgery is difficult to perform accurately. Moreover, the lenses which are available for such vision correction are not entirely satisfactory for a variety of reasons, including a tendency to shift out of position after placement, to impair transcorneal gas diffusion, to be excessively thick, or to be unable to correct presbyopia or astigmatism.
Accordingly, there exists a need for a method and device for correcting visual abnormalities through surgical implantation of an appropriate corrective lens within the cornea an eye in such a way that the lens may be reliably placed and will remain properly positioned and oriented, to enable reversible correction of a wide range of visual abnormalities.
SUMMARY OF THE INVENTION
The present invention solves the above-noted need by providing a method and devices for intracorneal lens placement. A specially adapted lens is implanted in a corneal pocket which has been precisely formed by a device which creates and shapes the pocket to accept and retain a lens in the cornea. Whereas in typical corrective surgery an entire flap of the cornea is lifted as shown in
FIG. 2
a
to permit access for further surgical modification of the cornea, in vision modification according to the present invention a flap of cornea is not lifted, but rather a pocket is formed in the corneal tissue as shown in
FIG. 2
b
. As much of the corneal surface as practical is left intact to simplify healing and to discourage movement or loss of the inserted lens.
In order to position a lens within the cornea of an eye in a precisely predictable and repeatable manner, and to help retain the intended orientation and positioning of the lens while the eye heals from surgery, the present invention provides a corneal pocket keratome to create a pocket of precise dimensions in the cornea, and also a lens having special features to establish a close fit between the lens and the corneal pocket. Both of these pieces can be realized in a number of different embodiments. Moreover, the corneal pocket keratome has several subparts, each of which can be realized in many ways.
The lens size and shape matches the corneal pocket formed by the corneal pocket keratome, and provides desired focal modifications when disposed within corneal tissue. The lens permits sufficient gas diffusion to allow adequate oxygenation of internal eye tissues. In preferred embodiments, lens features create an interference fit between the lens and the corneal tissue at the edges of the corneal pocket to aid in retaining the placement and orientation of the lens. In addition to a precise fit, such retention features of the lens may include a material which swells when hydrated after placement within the cornea, or variations in the radius of the lens to form circumferential bumps. The lens may accordingly have an asymmetric, radially and/or axially varying focus to compensate for the effects of astigmatism or presbyopia, generally in addition to compensation for myopia or hyperopia. For some applications, lens thickness may be desirably reduced by employing a Fresnel intracorneal lens.
The corneal pocket keratome preferably includes a surgical unit having cutting head elements mounted on a keratome drive assembly, and also a control unit and a footpedal. During formation of a pocket in the cornea, the cutting head elements are in intimate contact with the subject eye, either to position the eye or to create an incision. The control unit supplies power and vacuum to control the surgical unit according to settings entered by the user, and in response to commands made using the footpedal. The surgical unit is preferably hand-held and easily positioned over the subject eye.
The preferred surgical unit may include four distinct elements. Three of these are “cutting head” elements which contact the eye during corneal surgery—a positioning ring assembly, a corneal support assembly, and a corneal pocket blade assembly. Preferably, each of these three cutting head elements extends from the fourth element, a keratome drive assembly, which drives the corneal pocket blade assembly with respect to the other two cutting head elements in such a way that interference and rubbing between parts of the corneal pocket keratome is minimal or entirely absent near the surgical site. It is also preferred that each of the three cutting head elements is easily removed and as easily replaced onto the fourth element, the drive assembly, without a need for tools, so the surgeon can ensure sterility by simply replacing the cutting head elements. Ease of replacement also enables the surgeon to readily select different styles and sizes of cutting head elements, as desired for a particular operation.
The subject eye is held in a position by a positioning device, which is typically a positioning ring attached to the keratome drive assembly. The positioning ring is supplied with vacuum which draws the eye into the ring causing the cornea to protrude through the ring. Then, in most applications the protruded cornea is pressed against a corneal support assembly which is also attached to the keratome drive assembly. The corneal pocket blade assembly is attached to a driving member of the keratome drive assembly such that a corneal pocket blade of the assembly is positioned near the corneal support assembly. Upon direction from the operator, the keratome drive unit imparts a compound movement to the corneal pocket blade through the driving member, driving the blade forward into the cornea while also causing the blade to oscillate laterally.
The blade preferably travels within a cutting plane which is controlled with respect to the corneal surface. The corneal surface is typically disposed against the corneal support assembly. The precise position of the cutting plane with respect to the corneal surface may be controlled by a guide which is supported by, and travels along with, the corneal pocket blade assembly and directly contacts the cornea. Alternatively, the cutting plane may be maintained at a known distance from the corneal support assembly. The distance may be controlled by a guide portion of the corneal pocket blade assembly which interferes with the corneal support assembly during cutting. Such interfering guide, if used, may contact the cornea or may be positioned to avoid such contact. The cutting plane to corneal support distance may also be controlled directly by the mechanical connection between the corneal support surface, the keratome drive assembly, and the corneal pocket blade assembly. By thus controll
Cohem Lawrence S.
Willse David H.
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