Surgery – Devices transferring fluids from within one area of body to...
Reexamination Certificate
2001-06-04
2002-12-17
Prebilic, Paul B. (Department: 3738)
Surgery
Devices transferring fluids from within one area of body to...
C623S004100
Reexamination Certificate
active
06494857
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for selectively improving and/or permanently ensuring the permeability for ocular aqueous humour through the trabecular formations into Schlemm's canal.
2. Description of the Prior Art
In cases where the aqueous humour cannot escape from the intra-ocular cavity sufficiently the intra-ocular pressure increases, which intensifies the risk of formation of glaucoma. The glaucoma is a particular form of optic nerve atrophy that is predominantly induced by an intra-ocular pressure too high for a healthy functioning of the nerve.
As a consequence, the reduction of the intra-ocular pressure at least to values within the limits of statistical normal (statistical WLN) is the primary aim of any therapeutic approaches in glaucoma treatment.
The reduction of the ocular pressure can be achieved by a number of medicaments, by laser methods in so-called argon laser trabeculoplasty (ALT) or by surgical procedures in a fairly narrow sense. Disadvantages entailed by a therapy based on medication are an only restricted pressure reduction potential, undesirable side effects and, above all, the necessity of life-long application several times a day, which involves naturally problems of reliable application (compliance).
Disadvantages entailed by argon laser trabeculoplasty are their reduced pressure reduction potential and their only transient efficacy as the effect is reduced in the course of time.
Among the surgical procedures the so-called firstling techniques are the operative standard today. Among their numerous disadvantages, the substantial potential of post-operative complications should be particularly emphasized, apart from the accelerated formation of a cataractous lens, the unpredictability of the effect that may range from excessive reduction of the pressure up to a rapid cicatrizationg with an entire loss of the pressure-reducing effect.
This entirely unsatisfactory balance of success and the insufficient predictability of the success of this standard procedure has resulted in a great number of other surgical approaches among which the trabeculotomy and the deep sclerotomy should be mentioned particularly, which are both surgical techniques permitting a facilitated outflow of the aqueous humour by the provision of physiologic excretory or drain ducts. These techniques, too, involve, however, the particular disadvantage that their effect may be lost again, either partly or entirely, as a result of wound healing processes.
The following explanations are intended to facilitate the understanding of the glaucoma problems:
The space between the crystalline lens and the posterior cornea surface, which is subdivided by the iris into the posterior and the anterior chambers of the eye, is filled with aqueous humour. The aqueous humour is permanently produced by the ciliary body, the corpus ciliare, of the eye and is discharged into the posterior chamber of the eye. The aqueous humour then flows from there through the pupil into the anterior chamber of the eye, where it is subjected to a heat flow, and arrives from there into the iridocorneal angle through the meshwork of the corneoscleral trabecular formations into Schlemm's canal, also referred to as the venous sinus of the sciera. The aqueous humour finally flows from there through excretory ducts into the venous system of the eye surface.
The secretion and outflow of the aqueous humour in a homeostatic balance serves the purpose of maintaining an intra-ocular pressure at a constant level within narrow limits, which must, however, be sufficiently high in order to retain the dimensional stability of the eye, and low enough in order to avoid any obstruction of the nutrition of the optic nerves. Values within the range from 10 mm Hg to 20 mm Hg are roughly considered as standard range for the intra-ocular pressure. There is, however, no clear distinction between normal values and increased pathological values: the transition is fluid, with an ever-increasing probability of a glaucoma disease as the levels of the intra-ocular pressure are rising.
A pathological increase of the intra-ocular pressure may fundamentally be caused by both excessive secretion of aqueous humour and insufficient outflow. For the purposes of the present description only the increase of the outflow obstruction in the juxta-canalicular trabecular formations will be discussed here, which constitutes the basis of the so-called primary chronic glaucoma simplex, which obstruction is quoted in the scientific literature as accounting for 85 to 90% approximately of all of these glaucoma constellations.
The chronic glaucoma simplex accounts, in its turn, for more than three quarters of all glaucoma cases. The causes of this increase of resistance in the juxta-canalicular trabecular formations are, in the last analysis, not clarified in all details. Genetic factors, the deposition of substances on the meshwork with a restriction of the mesh aperture and hence an increase of the resistance, as well as a mechanical collapse of the meshwork are aspects deemed to be established facts.
The principle of trabeculotomy as applied nowadays is as follows: Starting out from the trabeculotomy technique known per se, Schlemm's canal is located and opened from outside. Then a metal probe is introduced into the canal and pivoted into the anterior chamber. Such an operation actually tears the trabecular formations in their entirety, however, so that an open communication is established between the anterior chamber of the eye with the aqueous humour circulating therein and Schlemm's canal.
The anatomic structure of the trabecular formations, where the increased outflow obstruction is located, is, however, actually destroyed by the aforedescribed approach. Even though this surgical method initially furnished only hardly convincing results it gained importance substantially throughout the past few years due to refined techniques. There is no other method, for instance, by which the pressure-reducing success produced by this approach has been achieved under certain conditions. It involves, however, the inherent problem that the two ends of the opened distance may close again so that only the actually torn-up passage, rather than the entire canal range, is available for outflow.
To this adds the aspect that the torn-up trabecular formations may conglutinate again in certain cases as the two torn-up parts of the trabecular formations are closing, so to speak in the manner of the wings of a door. Such resealing is promoted by reflux bleeding from the venous system communicating with Schlemm's canal.
The European Patent EP 0 550 791 Al, for instance, discloses a surgical instrument specifically configured for the selective injection of a highly viscous medium into the trabecular formations. This instrument is, in particular, a surgical probe that is introduced into Schlemm's canal during the operation and subsequently removed completely from this canal after the treatment.
The probe with its arcuate configuration presents openings on the internal side of the arc, through which the highly viscous medium is injected into the trabecular formations. To this end the curved probe is connected to an injection introduced into Schlemm's canal. A detailed representation of this mode of operation of the injection procedure is apparent from FIG.
2
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The known device constitutes a surgical instrument for performing a surgical procedure on the eye for local dilation of the trabecular formations by selective injection into this system in an approach to improve its permeability to the aqueous humour.
A comparatively small opening in the trabecular formations would, in principle, be sufficient to permit the desired effect of intra-ocular pressure control if it could be ensured that the opening will not be closed again so that the aqueous humour will gain access through this gap, even though this gap is admittedly small, to Schlemm's canal in its entirety and hence to the natural outflow
Antonelli Terry Stout & Kraus LLP
Matthews William H
Prebilic Paul B.
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