Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Acyclic nitrogen double bonded to acyclic nitrogen – acyclic...
Reexamination Certificate
2000-11-08
2004-04-13
Travers, Russell (Department: 1617)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Acyclic nitrogen double bonded to acyclic nitrogen, acyclic...
C514S150000, C514S657000, C514S728000, C424S009600, C424S009610, C600S558000, C604S028000
Reexamination Certificate
active
06720314
ABSTRACT:
The invention relates to the field of ocular surgery, in particular to surgical procedures for cataract extraction.
In the normal eye, the crystalline lens is located behind the iris, and in front of the corpus vitreum. The lens is transparent, biconvex, accounts for about 20 diopters of convergent refractive power of the eye, and it is composed of a capsule that encloses and encompasses the lens substance, i.e. the lens epithelium, the cortex, and the nucleus. A ring of zonular fibers, that extend from the ciliary body to the anterior part of the lens capsule, keeps the lens positioned within the eye.
The capsule is an elastic, type IV collagen basement membrane produced by the lens epithelial cells. The thickness of the capsule varies from 4-24 &mgr;m, with a thickness of about 14 &mgr;m at its anterior part, 24 &mgr;m at its equatorial part, and about 4 &mgr;m at its posterior part. Because of its transparency, and because its refractive index nearly equals the lens substance, the lens capsule can not be discriminated from the lens substance, except with the use of a slit-lamp at high magnification.
The lens substance may become less transparent, i.e. a cataract may develop, due to aging or to a wide variety of ocular or systemic pathological disorders or diseases. Affected portions of the lens substance may differ with the type of disorder, but in most cases the optical and/or refractive functions of the lens are compromised, for example a decreased visual acuity, a decreased contrast sensitivity, an accommodation loss, etc.
To restore the optical pathway, cataract surgery may be performed to remove the opaque lenticular mass. Although various surgical techniques are available, extracapsular cataract extraction techniques, the Blumenthal technique, or phacoemulsification are most often used. With all techniques, the anterior chamber of the eye is opened through a peripheral corneal, limbal or scleral incision, the anterior lens capsule is opened, and the lens substance is removed, while leaving the peripheral rim of the anterior lens capsule as well as the capsular equatorial and posterior portions in-situ. The empty lens capsule forms a capsular ‘bag’ that can be used to support a synthetic intraocular implant lens (IOL), so that an IOL is positioned ‘in the bag’.
Various techniques are used to open the anterior lens capsule, i.e. the excision of a portion of the anterior lens capsule, with or without the use of a viscous or viscoelastomeric substance, for example the can-opener technique, the envelop technique, the capsulotomy, and the continuous circular capsulorhexis. To visualize the capsular defect during the opening of the capsule, the red fundus reflex, the co-axial light of an operating microscope that is reflected from the posterior pole of the eye, is commonly used. When retroillumination is absent, for example with dense cataracts, heavily pigmented fundi or a combination of both, it is often not or only hardly possible to discriminate the anterior capsule from the underlying lens tissue.
Visualization of the defect in the anterior capsule during the opening of the lens capsule is an important step in the surgical procedure, because the mechanical traction forces which the capsule can withstand during surgery, vary with the configuration of the capsular opening. For example, in phacoemulsification a continuous circular capsulorhexis is commonly performed, because a circular configuration of the capsular opening can withstand best the surgical manipulations within the lens capsule during the removal of the lens substance. Improper visualization of the anterior lens capsule during the performance of a capsulorhexis may be responsible for a risk of a radial tear toward or beyond the equator of the lens capsule, and associated complications, for example vitreous loss, or a dropped nucleus.
Furthermore, in a subsequent phase of the surgery the outline of the opening in the anterior lens capsule is often difficult to visualize. During the removal of the lens substance in phacoemulsification a useful red fundus reflex is nearly always absent, because the lenticular tissue becomes opaque. However, during phacoemulsification it still is important that the rim of the capsulorhexis is not damaged, so that the capsular integrity is maintained during the surgical manipulations within the capsule. For example, an inadvertent touch of the rim with the tip of the phacoemulsification hand piece or an overextension of the capsule during dividing the lenticular substance, may damage the rim of the capsulorhexis. Again, the damaged rim may give a greater risk of a radial tear toward the equator and associated complications, especially because the damage to the rim of the capsulorhexis may not be noticed during surgery.
During implantation of an IOL, the rim of the anterior capsule must be visualized to place the haptics of the IOL in between the anterior and posterior portions of the lens capsule. In this phase of the surgery, the anterior capsular rim can often be seen with the use of the red fundus reflex. To determine if a haptic(s) is positioned underneath the anterior capsular rim, the IOL is manipulated in such a way that the displacement of the capsular rim by the haptic or optic of the IOL indicates the position of the IOL relative to the capsule. In cases where a useful red fundus reflex is absent, as mentioned above, it becomes difficult to determine the position of the IOL relative to the capsule. Thus, there is a risk of the IOL being inserted in the area between the iris and the anterior lens capsule, for example the ciliary sulcus. Improper positioning of an IOL (that was designed to fit into the capsular bag) may be complicated by dislocation of the IOL after surgery.
In a letter to the Editor of the Journal of Cataract and Refractive Surgery (Hoffer K J, McFarland J E, “Intracameral subcapsular fluorescein staining for improved visualization during capsulorhexis in mature cataracts”, J Cataract Refract Surg 1993;19:566), K. J. Hoffer and J. E. McFarland have addressed the above problems associated with the poor visibility of the anterior capsule during the performance of the capsulorhexis, in particular in the presence of a mature cataract. They suggest that the problems may be overcome by injecting a solution of fluorescein underneath the anterior chamber. During the capsulorhexis, the capsule would be better visible due to it being stained by the fluorescein dye.
Fluorescein is a dye which is capable of diffusing through various tissue structures (see e.g. Brubaker R F, “Clinical evaluation of the circulation of aqueous humor”, in Tasman W, Jaeger E A, “Duane's clinical Ophthalmology”, Volume 3, Chapter 46, Philadelphia, JB Lippencott Co, 1994:1-11; or Friberg T R, “Examination of the retina: principles of fluorescein angiography”, in Albert D M, Jakobiec F A, “Principles and practice of ophthalmology”, Volume 2, Philadelphia, WB Saunders Co, 1994;697-718.). Consequently, when used as suggested by Hoffer and McFarland, fluorescein will not only stain the anterior lens capsule, but also the material below said capsule, particularly as the fluorescein is injected underneath the anterior lens capsule. This means that both the anterior lens capsule as well as the underlying lenticular tissue are stained by the fluorescein dye. Thus, no difference in staining can be observed between the anterior capsule and the underlying tissue during the capsulorhexis, and the desired improved visibility is not, or not sufficiently, achieved.
Moreover, it was noted by Hoffer and McFarland that the sodium hyaluronate, which is used during the operation to fill the anterior chamber of the eye, may become stained and may have to be replaced with fresh sodium hyaluronate. Of course, it is undesired to have to interrupt the course of the surgical procedure to replace the gel layer.
The present invention seeks to overcome the above described problems associated with poor visibility of the lens capsule during cataract surgery. It is an object of the invention to make it possible to v
Banner & Witcoff , Ltd.
Sharareh Shahnam
Travers Russell
LandOfFree
Use of a vital dye for facilitating surgical procedures for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Use of a vital dye for facilitating surgical procedures for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Use of a vital dye for facilitating surgical procedures for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3229106