Surgery – Instruments – Corneal cutter or guide for corneal cutter
Reexamination Certificate
1999-12-28
2001-07-03
Recla, Henry J. (Department: 3731)
Surgery
Instruments
Corneal cutter or guide for corneal cutter
Reexamination Certificate
active
06254619
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Art
The invention is directed to a corneal surgery apparatus. In particular, this invention is a microkeratome instrument for use in refractive surgery.
2. Discussion of Background and Prior Art
Correctable conditions of the optical system in the eye are known. Myopia (nearsightedness) is a condition where the visual images come to focus in front of the retina of the eye resulting in defective vision of distant objects. Hyperopia (farsightedness) is a condition in which visual images come to focus behind the retina of the eye and vision is better for distant objects than for near objects. Astigmatism is a condition in which light rays from a point fails to meet in a single focal point, resulting in a blurred and imperfect image. In the human eye this defect of vision due to astigmatism is typically due to a corneal irregularity.
Refractive surgery is a known method of treating myopia, hyperopia, astigmatism, and certain corneal abnormalities. This process involves reshaping various layers of the cornea to change the refractive surface thereof. Numerous methods of refractive surgery have been developed, including radial keratotomy (where radial slits are cut into the cornea to correct myopia), automated lamellar keratoplasty (“ALK”, where a first flap is created in the upper layer of the cornea with a microkeratome, then additional corneal tissue is removed to correct vision), laser photorefractive keratectomy (“PRK”), among other methods. Presently, LASIK (the acronym for “laser assisted in situ keratomileusis”), has gained popularity. In the LASIK procedure, an excimer laser is used to reshape the cornea after a thin layer of the cornea (a corneal flap) is raised in a procedure called a keratectomy. The excimer laser is used to ablate selective areas of the cornea under the incision, and thereafter the corneal flap is returned to its position, where it quickly heals.
A critical part of the LASIK procedure is cutting a generally circular flap on the top surface of the cornea, in a procedure called a keratectomy. The device used to do this is the microkeratome. Numerous different styles of microkeratomes are available. These prior art microkeratomes include an eye engaging portion that has an aspiration ring for securing the eye engaging portion to the eye, an applanate plane against which the cornea of the eye will press flat against, and a rapidly oscillating blade placed in close proximity to the applanate plane which are used slice the thin corneal flap. These different styles of microkeratomes are designed to be used with a speculum. After the flap is cut and folded back, an excimer laser is used to remove corneal tissue under the cut flap and reshape the cornea. Thereafter, the flap is laid back on top of the excised area. Use of a speculum during keratectomy can cause patient discomfort, and cause involuntary eye movement.
Furthermore, in some presently available microkeratomes, a head portion with the microkeratome blade must be carefully aligned with the eye engaging portion after the eye engaging portion is fitted to the eye which can be difficult to do.
In other microkeratome designs, the head portion is engaged with the eye engaging portion prior to placement on the eye. However, these designs tend to be bulky, reduce access to the surgical field, and can be awkward to place and remove from the eye.
The prior microkeratomes also either do not permit simple adjustment of the size of the uncut corneal flap or have bulky mechanisms.
A further inadequacy with some prior microkeratome designs is that their motorized handpieces are noisy, which further raises the anxiety level of the patient and can cause eye movement.
Other shortcomings with some presently available microkeratome include the quality of the corneal flap created during the keratectomy, the need to calibrate the depth of the cut (e.g. by adjusting the position of the applanata plane), and the difficulty in easily and consistently selecting the desired corneal flap thickness from procedure to procedure.
Yet a further shortcoming of present microkeratomes is that they can be troublesome to clean and sterilize. Indeed, disposable microkeratomes are now available to reduce sterilization downtime.
There accordingly remains a need for an improved microkeratome that addresses the above concerns.
SUMMARY OF THE INVENTION
Most microkeratomes have some common elements. A positioning assembly with a suction ring is provided for application to the cornea of the eye and is temporarily fixed there by suction being applied. A considerable amount of suction is required to hold the suction ring in place, and as a result, the surgeon must carry out the keratectomy relatively quickly. The top surface of the base portion has a flat surface. A head portion is engaged with the base portion. The head portion has a rapidly moving blade provided therein and an applanate plate that is used to slice a very thin top layer of cornea. A motorized microkeratome handpiece attaches to the head portion and moves the blade.
The positioning assembly has two spaced apart guide walls and that are raised above a platform surface higher than guide walls of prior art designs. These two guide walls permit the surgeon to conduct the keratectomy without using a speculum to forceably hold the lids of the eye open since the raised walls themselves will prevent the lids from impinging on the surgical field during the keratectomy. With prior art microkeratomes, they sometimes impinge on the speculum, or worse yet, pinch the eye lid against the speculum, which can be very painful.
The guide walls of the positioning assembly include slide surfaces that interact with complementary slide surfaces of the head portion, including beveled entry points on the slide surfaces of the base portion and head portion. These beveled surfaces aid the surgeon in sliding the head portion into the positioning assembly quickly and securely after the positioning assembly is placed on the cornea and aspiration is applied to retain the positioning assembly in place. In prior designs, this has sometimes presented a challenge to the surgeon, particularly less experienced surgeons.
Another aspect of the invention includes the feature that the head portion has a base portion with an insert portion, with the insert portion being detachably and pivotally engaged with the base portion to allow for easy and through sterilization between uses of the microkeratome. By designing the insert portion to be detachably retained to the base portion, different insert portions can be provided for use with a standardized base portion. These different insert portions can accommodate specialized needs, including slightly different cutting depths.
Another feature of the invention is its compact and optionally adjustable stopping means used to prevent the head portion and its blade from pushing through the top layer of cornea and entirely cutting off the corneal flap.
Yet another feature of the invention that works in concert with the new design of microkeratome is a new design for a microkeratome handpiece that has a brushless DC motor, which generates more torque, a wider range of speeds (e.g. 5,000 rpm to 40,000 rpm), and does so more quietly, which further prevent the patient from becoming nervous during the refractive surgical procedure. As noted above, the more relaxed the patient is, the less chance there is of the patient's eyeball excessively moving during the procedure.
These and other aspects of the microkeratomes of the invention are further described below.
REFERENCES:
patent: 5133726 (1992-07-01), Ruiz et al.
patent: 5290301 (1994-03-01), Lieberman
patent: 5342378 (1994-08-01), Giraud et al.
patent: 5441511 (1995-08-01), Hanna
patent: 5464417 (1995-11-01), Eick
patent: 5486188 (1996-01-01), Smith
patent: 5496339 (1996-03-01), Koepnick
patent: 5586980 (1996-12-01), Kremer et al.
patent: 5591174 (1997-01-01), Clark et al.
patent: 5595570 (1997-01-01), Smith
patent: 5624456 (1997-04-01), Hellenkamp
patent: 5653723 (1997-08-01), Kamerling et
Garabet Antoine
Kuklin Yevgeniy
Christie Parker & Hale LLP
King Anthony S.
Recla Henry J.
LandOfFree
Microkeratome does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microkeratome, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microkeratome will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2505682