Surgery – Magnetic field applied to body for therapy – Magnetic element placed within body
Reexamination Certificate
1999-12-27
2001-10-23
Winakur, Eric F. (Department: 3736)
Surgery
Magnetic field applied to body for therapy
Magnetic element placed within body
C600S009000, C606S005000, C606S027000, C607S053000
Reexamination Certificate
active
06306075
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to devices and techniques for non-contact thermal treatment of a patient's cornea for altering anterior corneal curvature to correct refractive disorders, and more particularly, to implantable intrastromal segments that may be elevated in temperature by magnetic induction to cause lesions in, or shrinkage of, the Bowmnan's layer and/or stromal lamellae to increase corneal steepness in hyperopic or presbyopic refractive treatments.
2. Description of the Related Art
Refractive disorders of the eye result from the inability of the eye's optic system, consisting of the dome-shaped cornea and the crystalline lens just behind it, to properly focus images on the retina, the nerve layer at the back of the eye. Approximately 80 percent of the refracting power of a human eye is within the cornea. When the cornea is mis-shaped, or the eye is too long or too short along its optical axis, or when the lens of the eye does not function normally, a refractive error occurs. Refractive errors generally include hyperopia, myopia, presbyopia and astigmatisms. Hyperopia is a refractive error that causes poor close-up vision, and is caused by a flattened cornea or by a shortened eye that focuses images beyond the retina (see FIG.
1
A). Myopia is the opposite and causes poor distance vision, and is characterized by an elongate eye or steepened corneal shape. This condition causes distant images to focus in front of the retina rather than directly on it (see FIG.
1
B). Presbyopia results from aging and is a form of farsightedness caused by diminished ability of the lens to elastically change to refract light. Astigmatism is a condition which causes blurred vision for both near and far objects. In an astigmatic patient, the cornea may be shaped like the back of a spoon rather than having a spherical shape. Such an asymmetric corneal shape creates different retinal focal points. Hence, instead of images focusing on the retina, the images focus on a number of points around the retina resulting in a blurred image.
The optimal shape for a cornea is that of a perfect sphere assuming that axis of the eye is normal relative to the other eye. Glasses and contact lenses correct refractive errors by refracting (bending) light before it reaches the cornet and is transmitted through the lens, in other words, changing the angle at which light enters the cornea.
Several types of surgical procedures have been developed to correct refractive disorders such as myopia, hyperopia and astigmatisms by changing the shape of the cornea. For example, laser procedures can reshape the patient's cornea to some extent to a corrected more spherical shape, the most common procedures being laser in-situ keratomileusis (LASIK) and laser photorefractive keratectomy (PRK). LASIK and PRK correct vision by recontouring the anterior layers of the cornea by means of surface ablation with a laser.
It is useful to provide a description of the anatomy of the patient's eye.
FIG. 1C
depicts patient's eye
5
which comprises a system of cornea
6
and lens
3
which focuses light on the retina indicated at
4
which is at the back of the substantially spherical body defined by sclera
7
. The anterior chamber
8
(and aqueous
9
a
therein) is separated from the vitreous body
9
b
by lens
3
. Thus, cornea
6
forms the anterior wall of chamber
8
and also acts as a lens element. The cornea
6
is a smoothly curved transparent structure which has a smaller radius of curvature than the opaque sclera
7
and bulges from the smooth outer spherical surface of the eye. Refractive errors occur when the cornea and lens do not focus incoming light on retina
4
.
The cornea
6
is uniquely structured to transmit light into the eye. The primary structure of the cornea is the stroma, which comprises approximately 90 percent of the cornea's thickness. The stroma is comprised of lamellae which lie in flat sheets and extend from limbus to limbus. Each lamella (layer or sheet) consists of strong, parallel collagen fibrils which are maintained in a regularly spaced hexanal separation by a ground substance or GAGs (for glycoaminoglucans, also called a glycolprotein and mucopolysaccharide matrix). Between the lamellae are keratocytes layers (the fibroblasts), the constitutive cells of the cornea which produce the GAGs and support synthesis of collagen. It is well known that the elongate stromal collagen fibrils may be longitudinally contracted by application of heat to temperatures above about 60° to 65° C. See, e.g., U.S. Pat. No. 4,461,294 issued to Baron; U.S. Pat. No. 4,976,709 issued to Sand; U.S. Pat. No. 4,326,529 and U.S. Pat. No. 4,381,007 issued to Doss; and U.S. Pat. No. 5,533,999 issued to Hood.
SUMMARY OF THE INVENTION
The invention is termed herein a MI
3
system and technique (magnetoresonant induction of intrastromal implant) for re-shaping a pattient's corneal by contracting collagen fibrils to form a circumferential “cinch” or “ring” around the cornea. The MI
3
system and technique may be utilized to correct mild to high hyperopia and presbyopia by steepening the anterior corneal curvature in a single treatment, or in periodic treatments over the lifetime of the patient.
The MI
3
system is a combination including (i) at least one magnetoresonant implantable intrastromal segment, and (ii) an oscillating magnetic field generator together with a dosimetry control system. At least one emitter is provided and is adapted for positioning proximate to the patient's eye and the intrastromal implant. Thus, the MI
3
system is adapted to deliver thermal effects to appropriate stromal lamellae by non-contact inductive heating of the implant which in turn contracts or compresses stromal collagen fibrils into a circumferential cinch within an anterior layer of the cornea to steepen the anterior corneal curvature. The dosimetry control system controls the power level and duration of exposure of the oscillating magnetic field(s).
In general, the present invention advantageously provides a system that will require less than a few minutes of procedure time to correct corneal curvature in an office setting, once the magnetoresonant implants are in place.
The invention advantageously provides a “norn-contact” system of delivering thermal energy to collagenous tissues to correct corneal curvature in hyperopic or presbyopic patients.
The invention advantageously provides a system for correcting hyperopic or presbyopic errors in periodic treatments over the lifetime of the patient.
The present invention provides a system that can correct vision without invasion of the patient's visual axis.
The present invention advantageously provides a system having an arrangement of a plurality of N oscillating magnetic field emitters positioned about a central axis of the system and the patient's optical axis to allow such axes to be free for concurrent adjunctive diagnostic or therapeutic systems, such as intraoperaive corneal topography.
The invention advantageously provides a system having N emitters that allows opposing emitters to direct oscillating magnetic fields at opposing quadrants of the cornea and implants therein simultaneously to provide a substantial symmetry of treatment.
The invention further advantageously provides a system having N emitters that allows each of the N applicators to direct oscillating magnetic fields at opposing quadrants of the cornea at independent power levels to provide a refiled method of energy delivery to spaced apart implants portions for treatments of astigmaitisnm.
The invention advantageously provides a system of delivering thermal energy to the Bowman's layer or stroma without ablating epithelial layers.
The invention advantageously provides a device having a system of delivering thermal energy to a mid-stromal regions without the high peak temperatures associated with pulsed lasers.
The invention advantageously provides a system for contracting stromal collagen while using a heat-sin
Hann James F.
Haynes Beffel & Wolfeld LLP
Natnithithadha Navin
Winakur Eric F.
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