Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2001-02-28
2004-01-20
Paik, Sang Y. (Department: 3742)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S177000, C623S006560, C623S006580, C623S907000, C623S005160
Reexamination Certificate
active
06679605
ABSTRACT:
Eye surgeries involving ophthalmic devices usually require an incision for introducing the ophthalmic device to the target location for their intended use. Often, it is desirable to make the incision size as small as possible for fast recovery and for minimizing potential post-operational complications and side effects. In order to understand this general small incision concept, the following examples are given for the purpose of illustration, but not to limit the scope of the present invention.
Intraocular lenses (IOLs) have been used as the replacement for the crystalline lens after cataract surgery and as a phakic lens which functions together with the intact crystalline lens for correcting refractive errors. To surgically implant an intraocular lens (IOL) or phakic lens into the eye, an incision is made on the cornea. It is desirable to keep the incision size as small as possible. Implanting a traditional polymethyl methacrylate (PMMA) IOL or a PMMA phakic lens requires an incision size of about 6 mm simply because the hard PMMA lens has an optical diameter of approximately 6 mm. In order to reduce the incision size, soft materials, such as silicone or soft acrylic material have been used for lenses. A soft lens can be folded in half and then implanted into an eye with an incision size of about 3 mm. The reduction in incision size has been proven in clinical studies to reduce surgically induced astigmatism, hasten wound healing, and reduce risk of infection and/or inflammation.
Corneal inlay is an ophthalmic device surgically implanted within the cornea. A corneal inlay is designed as a lens, about 2 to 3 mm in diameter, which provides a central nearsighted vision zone for presbyopic patients. The natural cornea surrounding the inlay provides the patient with the farsighted vision. The human cornea has a thickness of approximately 0.5 mm. To implant a thin inlay lens into the cornea, the first step is to make an incision on the corneal surface without cutting through the whole corneal layer. The second step is to make a pocket within the corneal layer with the initial incision as the pocket opening. The incision should have a sufficient width so that the artificial inlay lens can be introduced into the pocket. For example, if a hard corneal inlay lens, such as a PMMA lens, is used, the minimum incision size needs to be about the same as the diameter of the PMMA lens. As with an IOL, a deformable inlay lens allows a reduced incision size and, therefore, reduced surgical trauma.
Cytomegalovirus (CMV) infection of the retina, or CMV retinitis, usually leads to blindness if untreated. CMV retinitis progresses very rapidly, particularly in HIV patients, often within weeks. One of the treatments is to introduce an anti-CMV drug inside the eye by a slow release drug delivery device through the cornea or the sclera. To implant the drug delivery device into the eye, a small incision or hole is cut through the cornea. Then the drug delivery device is pushed through the incision or the hole. For this application, it will be ideal if the drug delivery device is a hard solid rod for easy insertion. When the drug delivery device is inside the eye, it becomes soft. In addition, if the drug delivery device can be stretched into a smaller profile, it will be implanted into a reduced incision size or hole diameter. Therefore, surgical trauma is minimized.
From the examples given above, there is a need for ophthalmic devices which can be implanted into an opening which has a size smaller than the dimension of the ophthalmic device in its intended use conditions. Furthermore, the ideal ophthalmic device is a hard solid at the time of implantation so that it can be relatively easily implanted into the soft tissue opening. In addition, when warmed by the body temperature, the “ideal” hard solid ophthalmic device can become soft and pliable for optimal tissue compatibility.
The crystalline state of polymers is defined as one that diffracts x-rays and exhibits the first order transition known as melting (L. H. Sperling,
Introduction to Physical Polymer Science,
John Wiley & Sons, New York, 1992). As in small molecules, crystallinity occurs when parts of a molecule arrange themselves in a regular order or arrangement. Unlike a small molecule, polymers that crystallize in the bulk state are never totally crystalline, a consequence of their long-chain nature and the chain entanglements. Even in homopolymers, there will be crystalline and amorphous regions. Polymers that have crystalline regions may be referred to as crystalline or semi-crystalline polymers. The development of crystallinity depends on the structure regularity in the polymer. An increase in non-regularity of the polymer structure decreases crystallinity of the polymer and results in a lower melting temperature. The increase in non-regularity may eventually prevent crystalline regions from forming.
The present invention utilizes crystalline polymers which provide a novel mechanism for deforming ophthalmic devices made from those polymers into a smaller profile than their initial size, at least in one dimension, so that they can be implanted into the eye through a relatively small incision. When the ophthalmic device is placed in the targeted location, it will return to its intended shape and dimension or adapt to a new configuration shaped by the tissue surrounding the ophthalmic device.
The present invention includes crystalline polymers that may be useful in the production of deformable lenses such as IOLs for cataract surgery, corneal inlays, and phakic refractive lenses for correcting ametropia, such as myopia, hyperopia, astigmatism, and presbyopia. The present invention also includes the use of crystalline polymers in ophthalmic devices which are not lens related. Such non-lens related devices may include, but are not limited to, ocular drug delivery devices, and implants for reducing intraocular pressure in glaucoma patients.
Stoy in his U.S. Pat. No. 4,731,079, issued Mar. 15, 1988, discloses a method of introducing and implanting an artificial intraocular lens to replace a surgically removed human crystalline lens through a small incision. The artificial lens material has a softening temperature in the range of about 0° C. to about 42° C. The method comprises the following steps: First, heat the artificial lens to a temperature higher than its softening temperature; second, deform the artificial lens into a smaller profile at least in one dimension so that it can be implanted through a small incision into the eye; third, cool down the deformed artificial lens to a temperature which is at least 5° C. less than the softening temperature, so that the artificial lens will be frozen in the deformed configuration; fourth, implant the deformed lens into the eye through a small incision. After being warmed up by the eye temperature, the deformed lens will return to its pre-deformed shape and dimension. Stoy further teaches that preferred materials include terpolymers which contain both hydrophobic and hydrophilic monomers as well as a minor amount of monomers with at least two polymerizable double bonds. These terpolymers can be hydrated due to the presence of a desirable amount of hydrophilic monomers. The plasticizer, water in the case of the terpolymer, can lower the softening temperature of the lens material. Stoy indicates that the softening temperature may correspond to the glass transition temperature (T
g
). However, Stoy is silent on whether the softening temperature can be a melting temperature (T
m
). Those who are skilled in the art understand that only a crystalline polymer can have a T
m
and that a crystalline polymer is typically not transparent due to the presence of crystalline structure. According to Stoy, one of the requirements for his invention is that the material must be highly transparent to visible light. Stoy further teaches that preferred polymers for use in his invention are amorphous, without a substantial amount of crystalline polymer phase being present.
MemoryLens™, a commercially available implanta
Liau Christine
Valyunin Igor
Wilcox Christopher D.
Zhou Stephen Q.
Dahbour Fadi H.
Frost Brown Todd LLC
Medennium, Inc.
Paik Sang Y.
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