Abstract:
A glaucoma drain for non-penetrating deep sclerotorny is made of non-resorbable and hydrophilic synthetic material. The drain is configured to be entirely covered by the scleral flap and totally inserted in the intrascleral space. It comprises a transverse bar ( 110 ) at one front end of the drain and a longitudinal body ( 120 ) extending longitudinally from said transverse bar. The transverse bar ( 110, 10 ) is configured to run along and cover the Schlemm&#39;s canal (CS) and the opposite ends are configured to penetrate beneath the deep sclera inside the Sclernm&#39;s canal. A hole ( 125 ) between the arms of the bar provides a target for possible YAG laser micro-punctures.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a glaucoma drain for facilitating the flow of aqueous humor through the trabeculo-descemetic membrane. 
   Glaucoma is a chronic, progressive and irreversible disease of having excessive intraocular pressure. When there is an obstacle to the evacuation of aqueous humor from the anterior chamber through a filter known as the trabeculum, the intraocular pressure increases and causes the progressive destruction of the nerve fibers. There are medical treatments whose efficacy proves to be insufficient in numerous cases in which solely surgery can enable the intraocular pressure to be reduced. 
   The purpose of surgical operation for the treatment of glaucoma is to create a mechanism for reducing the intraocular pressure. There are currently two main categories of drainage operation, penetrating and non-penetrating. The commonest surgery is penetrating surgery and is termed trabeculectomy. It consists in creating a fistula between the anterior chamber of the eye and a subconjunctival space. This operation requires, apart from opening the chamber, the formation of an aperture in the sclera using a scalpel, giving rise to complications which lead to a high number of failures. 
   2. Description of Related Art 
   The categories of non-penetrating surgical operations include viscanalostomy and deep sclerectomy, also termed ab externo trabeculectomy. Dr Robert Stegmman&#39;s viscanalostomy (J Cataract Refract Surg, vol. 25, 1999) comprises preparing a fornix based conjunctival flap and cutting a first parabolic flap of a third of the thickness of the sclera, and a second parabolic scleral flap of a depth of almost two thirds the thickness of the sclera which is later removed, de-roofing Schlemm&#39;s canal and injecting high viscosity non-crosslinked sodium hyaluronate into Schlemm&#39;s canal and subsequently under the outer flap after suturing. A scleral reservoir filled with sodium hyaluronate is thus formed under the outer flap. The physiological porosity of the juxtacanalicular trabecular meshwork and the descemetic membrane enable aqueous humor to be evacuated and the intraocular pressure to be reduced. However, the sodium hyaluronate is eliminated within five to six days and the reservoir rapidly fills up with fibrosis limiting the duration of effectiveness of the operation. 
   A development of this technique is presented in the PCT application WO 98/35640 which describes a pre-descemetic sclero-keratectomy implant of crosslinked hyaluronic acid having the form of a prism with a triangular base. This implant is supposed to occupy the surgically created space for a longer duration, but the volume of the implant reduces by half in four months and is totally resorbed subsequently. 
   According to another variant form of Dr Mermoud&#39;s deep sclerectomy, a glaucoma drain of cylindrical form is produced from lyophilized porcine collagen and is sutured in the deep scleral bed. The drain transports aqueous humor by capillarity. The superficial scleral flap does not close the posterior end of the cylindrical drain which is ill-adapted to the configuration of the scleral reservoir. The drain is resorbed in the month following the operation. 
   All these glaucoma implants and drains produced from crosslinked and non-crosslinked hyaluronic acid or from collagen are resorbable and thus do not constitute a truly long-lasting solution for draining aqueous humor from the anterior chamber so ensuring sustained reduction of the intraocular pressure. Moreover, these implants and drains of animal origin have a high manufacturing cost risk transmitting diseases, in particular viral diseases, and when they are of porcine origin or treated with porcine heparin, surgeons face refusal of patients on religious grounds. 
   The application WO 95/35078 describes a sclerectomy implant, with or without incision of the trabeculum, made from methylmethacrylate/vinylpyrrolidone copolymer with a high water content of the order of 40% It comprises an intra-scleral part adapted to be positioned against the trabeculum within an opening under the scleral flap and a sub-conjunctival part which emerges from the sclera and is lodged under the conjunctiva. The outer end of the implant pours aqueous humor under the conjunctiva and forms a bleb which is visible through the conjunctiva. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention relates to a glaucoma drain which is able to ensure drainage for extended periods or even indefinitely and does not have the drawbacks of known glaucoma drains and other sclerectomy implants. 
   According to a first aspect of the invention, a glaucoma drain for deep non-penetrating sclerectomy is made from non-resorbable hydrophilic material and characterized in that it is configured to be entirely covered by a scleral flap and completely inserted inside the intrascleral space. 
   By virtue of the hydrophilic nature of the drain, it participates itself in the passage of aqueous humor from the trabeculo-descemetic membrane to the intrascleral space where it is taken up by venous circulation. Lodged entirely inside the intrascleral space, it does not promote the formation of blebs under the conjunctiva. 
   Preferably the non-resorbable hydrophilic material that is also non-pyrogenic, and, of course, biocompatible, is 38% polyhydroxyethyl methacrylate (38% PolyHEMA) or a hydrophilic acrylic. Apart from the fact that these materials are not resorbable, they do not cause fibrosis like other non-resorbable biocompatible materials, and notably silicone. Consequently, the drain makes it possible to maintain around itself a permanent intrascleral space under the scleral flap which is favorable to the flow of aqueous humor for an extended period. As the drainage site then has little fibrosis, it can be serviced, in particular to reestablish the flow of aqueous humor. 
   Preferably, the present glaucoma drain is of one piece and comprises a transverse bar and a body which extends longitudinally from the transverse bar. 
   According to a preferred embodiment, the drain is in the form of a T comprising the transverse bar arranged at the front end and the longitudinal body which extends rearwards from the center of the transverse bar. 
   According to another preferred feature, the transverse bar comprises on the posterior surface a pair of projections on each side of a median zone which form a channel. 
   For a deep non-penetrating sclerectomy, the transverse bar extends along and partially covers the trabeculo-descemetic membrane and the ends of the transverse bar pass under the intact sclera and inside Schlemm&#39;s canal. In this position, the front edge of the drain is close to, and in practice in contact with the trabeculo-descemetic membrane. The length of the body is such that its rear end does not extend beyond the intrascleral space. 
   According to a second embodiment, at least a front portion of the drain is convex, such that, when the arms of the transverse bar are in register with the trabeculo-descemetic membrane, the front convex edge tensions that membrane in order to stretch the mesh and to increase porosity, and thereby the flow from the anterior chamber to the intrascleral space. 
   Preferably, a hole is provided between the arms of the transverse bar and constitutes a target for aiming the micro-punctures in the trabeculo-descemetic membrane produced by YAG laser, when they prove necessary to improve the evacuation of aqueous humor to the intrascleral space. 
   The features and advantages of the invention will also emerge from the following description, made by way of example with reference to the accompanying drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a glaucoma drain according to a first embodiment of the invention; 
       FIG. 2  is a view of the drain illustrated in  FIG. 1  lodged in the intrascleral space implanted before closing the superficial scleral flap; 
       FIG. 3  is a detail view of  FIG. 2 ; 
       FIG. 4  is a perspective view of a glaucoma drain according to a second embodiment of the invention; 
       FIG. 5  is a view of the drain illustrated in  FIG. 4  lodged in the intra-scleral space; 
       FIG. 6  is a perspective view of a glaucoma drain according to a third embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The glaucoma drain  1 , as illustrated in  FIG. 1 , is adapted to be implanted in the deep scleral bed (LS) in the course of a deep non-penetrating sclerectomy (see  FIGS. 2 and 3 ). 
   According to the present invention, the glaucoma drain is produced from a biocompatible material that is non-resorbable, hydrophilic and non-pyrogenic. This hydrophilic material is permeable to the aqueous humor, such that aqueous humor can pass via the drain, in particular via its so-called front end, close to, and in practice in contact with the trabeculo-descemetic membrane to its so-called rear end, to be taken up by the circulatory system. The water content is preferably high. The 38% polyhydroxyethyl methacrylate (PolyHEMA) and the hydrophilic acrylic copolymer, such as that commercialized by the corporation loltech under the trade mark POLY-MEGMA™, are suitable. 
   Such an implant enables in situ drainage for an extended period of several years, or even indefinitely, without modification of the geometry of the drain since the material from which it is made is non-resorbable in the implantation environment. The hydrophilic material from which the drain is preferably made does not cause fibrosis and thus makes it possible to maintain around itself an intrascleral space which is favorable to the flow of aqueous humor. Similarly, as the site has little fibrosis, it can be serviced in case of need. 
   The drain  1  comprises a transverse bar  10  and a longitudinal body  20 . The transverse bar  10  is situated at a so-called front end and comprises a pair of arms  11  extending in opposite directions. The longitudinal body  20  extends longitudinally towards the rear from the transverse bar. The general axis of the transverse bar  10  and that of the longitudinal body  20  are thus substantially perpendicular to each other. The longitudinal body preferably extends from the center of the latter and thus the drain  1  is generally T-shaped. 
   The outline of the drain is defined by the edges of the transverse bar  10  and of the longitudinal body  20  and comprises a front edge  14  of the transverse bar  10  extending between the rounded ends  13  of the bar which are continued by the lateral edges  15  of the other side of each of the arms and then by the lateral edges  24  of the longitudinal body  20  which terminate in a rounded end  23  at the rear end of the longitudinal body  20 . 
   The anterior face, not illustrated, is substantially planar and thus without relief portions. The same applies to the posterior surface  30  of the longitudinal body  20  and of the median zone  31  of the transverse bar  10  between the arms  11 . 
   According to a preferred embodiment, the posterior face of the arms  11  comprises a projection  12 , of generally tapered form and preferably semi-frustoconical of which the apex is situated at the rounded end  13  of the respective arms. 
   The median zone  31  located between the projections  12  forms together with them a channel adapted to direct the flow on the posterior surface rearward along the longitudinal body  20 . 
   An opening  22 , preferably circular, is formed at mid-height of the body  20  and on the longitudinal thereof. 
   In practice, the width of the transverse bar  10  is slightly greater than that of the removed deep scleral flap, such that the end portions  17  of the arms  11  can be introduced under the intact sclera inside Schlemm&#39;s canal (CS), as illustrated in  FIG. 2  and in detail in  FIG. 3 . The engagement by the end portions  17  of the respective arms ensures good positioning and orientation of the transverse bar  10  with respect to Schlemm&#39;s canal (CS) and the trabeculo-descemetic membrane. It is to be noted furthermore that the transverse bar  10  extends along and covers the trabeculo-descemetic membrane, the de-roofing of Schlemm&#39;s canal having been carried out beforehand, as positioned with respect to Schlemm&#39;s canal, and the front edge of the transverse bar is in contact throughout its length with the trabeculo-descemetic membrane (see  FIG. 2 ). 
   Once the terminal portions  17  of the respective arms are in place, the body  20  may be sutured to the scleral bed (LS) by means of the opening  22 . The superficial scleral flap (VS) may then be folded back and sutured followed by the conjunctival membrane. 
   The drain according to the invention ensures evacuation of aqueous humor into the intrascleral space formed under the scleral flap for an extended period by virtue of its both non-resorbable and hydrophilic nature. The drain makes it possible to maintain around itself a free permanent flow zone. Due to the high water content of the 38% polyHEMA or of the hydrophilic acrylic, aqueous humor may also pass via the drain to the circulatory system. The flow of aqueous humor is directed from the front end to the rear end and is favored by virtue of the channel defined between the projections on the posterior surface of the transverse bar. The configuration and the size of the drain enable implantation to be made entirely under the scleral flap and completely inside the intrascleral space. 
   If need be, the flow of aqueous humor may be increased by making micro-punctures by YAG laser in the region of the body of the drain  2  adjacent Schlemm&#39;s canal (CS). Moreover, the formation of a window in Schlemm&#39;s canal and the resulting positioning of the drain facilitate localization of the micro-punctures. 
   Nevertheless, according to an embodiment not illustrated, the projections may be eliminated such that the posterior face of the drain is substantially planar and thus without relief portions, like the anterior face. Similarly, although the T-shaped form, as illustrated, is preferred, other forms of the drain may be adopted. Whatever the case, the front edge must be positioned as illustrated in  FIG. 2 , that is to say close to and in practice in contact with the trabeculo-descemetic membrane. 
   In the hydrated state of the drain, the width of the transverse bar  10  between its opposite ends  13  is preferably 3 to 4 mm, or even greater, and more particularly approximately 4 mm. The height of the transverse bar defined between the front edge and the opposite lateral edge is of the order of 0.20 to 0.50 mm and preferably approximately 0.25 mm. The total height of the drain is preferably between 2.50 and 3.50 mm and in any case less than 4 mm, and the height of the body is approximately 2.75 mm. 
   The drain is preferably thin with a thickness of the order of 0.1 mm except for the thickness of the projection which is of the order of 0.30 mm. Thanks to that small thickness and the material it is made of, the drain may adapt itself to the curvature of the surface of the scleral bed. The thickness of the drain being of the order of that of the excised deep scleral bed, the drain may be entirely lodged inside the intra-scleral space after closing of the superficial scleral flap. 
   The glaucoma drain  100  according to a second embodiment, as illustrated in  FIG. 4 , is also adapted to be implanted in the deep scleral bed (LS) in the course of a deep non-penetrating sclerectomy (see  FIG. 5 ). 
   The glaucoma drain  100  is also produced from the same biocompatible, non-resorbable, hydrophilic and non-pyrogenic material as that of the first embodiment and enables the same implantation to be carried out, with the same functions and advantages as those of the first embodiment. 
   The drain  100  comprises a transverse bar  110  and a longitudinal body  120 . The transverse bar  110  is situated at a so-called front end and comprises a pair of arms  111  extending in opposite directions. The longitudinal body  120  extends longitudinally to a portion of the transverse bar. The general axis of the transverse bar  110  and that of the longitudinal body  120  are thus substantially perpendicular to each other. The longitudinal body preferably extends from the center of the latter and thus the drain  100  is generally T-shaped. 
   The outline of the drain is defined by edges of the transverse bar  100  and of the longitudinal body  120  and comprises a convex front edge  114  of the transverse bar  110  between the arms continued to the rounded ends  113  of the bar by straight lateral front edges  118  of the arms. The rounded ends  113  are continued by the lateral edges  115  parallel to the front lateral edges  118 , on the other side of each of the arms and then by the lateral edges  124  of the longitudinal body  120  which terminate with a slightly rounded end at the rear end of the longitudinal body  123 . 
   The anterior face, not illustrated, is substantially planar and thus without relief portions. The same applies to the posterior surface  130  of the longitudinal body  120  and of the median zone  131  of the transverse bar  110 . 
   The posterior face of the drain comprises, on each side of the median zone  131 , a projection  112 , of generally tapered form and preferably semi-frustoconical of which the apex is situated at the rounded end  113  of the respective arms. 
   The median zone  131  located between the projections  112  forms together with them a channel adapted to direct the flow on the posterior surface between the projections  112  and along the longitudinal body  120 . 
   An opening  122 , preferably circular, is formed in the body  120  at approximately three-quarters of the distance between the center of the anterior edge and the posterior end of the body and on the longitudinal axis thereof. 
   In practice, the width of the transverse bar  110  is slightly wider than that of the removed deep scleral flap, such that the end portions  117  of the arms  111  can be introduced under the intact sclera inside Schlemm&#39;s canal (CS), as illustrated in  FIG. 5 . The engagement by the end portion  117  of the respective arms ensures good positioning and orientation of the transverse bar  110  with respect to Schlemm&#39;s canal (CS) and the trabeculo-descemetic membrane. The transverse bar  110  extends along and partially covers the trabeculo-descemetic membrane, the ablation of the roof of Schlemm&#39;s canal having been carried out beforehand As positioned with respect to Schlemm&#39;s canal, at least the convex front edge  114  of the transverse bar is in contact with the trabeculo-descemetic membrane (see  FIG. 5 ) and the convex front edge  114  tensions it, such that its mesh, through stretching, increases the flow of aqueous humor through the trabeculo-descemetic membrane. 
   Once the terminal portions  117  of the respective arms are in place, the body  120  may be sutured to the scleral bed (LS) by means of the opening  122 . The superficial scleral flap (VS) may then be folded back and sutured followed by the conjunctival membrane. 
   The drain according to this second embodiment ensures the evacuation of aqueous humor in the intrascleral space and improves its flow through the tensioned portion of the trabeculo-descemetic membrane. 
   In case of need, the flow of aqueous humor may be increased by making micro-punctures by YAG laser. For this purpose, a second hole  125  is provided between the arms  112  and substantially in alignment with them. This hole constitutes a reference point and a target through which the doctor can direct the YAG laser in order to localize the micro-punctures in the region of the trabeculo-descemetic membrane. 
   Preferably, the width of the transverse bar  110  between its opposite ends  113  is 3.5 to 4 mm, or even greater, and preferably approximately 4mm. The width of the median zone  113  between the inner ends of the projections  112  is greater in this embodiment and in practice is of the order of 1.7 mm. The height of the transverse bar defined between the parallel lateral edges  115 ,  118  is of the order of 0.20 to 0.30 mm and preferably approximately 0.25 mm. The total height of the drain is preferably between 3 and 3.75 mm and is preferably approximately 3.50 mm. 
   The drain is preferably thin with a thickness of the order of 0.15 mm except for the thickness of the projection which is of the order of 0.30 mm, and is sufficiently flexible to follow the curvature of the scleral bed (LS). 
   In a third embodiment illustrated in  FIG. 6 , the glaucoma drain  2  comprises a transverse bar  50  and a longitudinal body  60 . The transverse bar  50  is situated at a so-called front end and comprises a pair of arms  51  extending in opposite directions. The longitudinal body  60  extends longitudinally to a portion of the transverse bar. The general axis of the transverse bar  50  and that of the longitudinal body  60  are thus substantially perpendicular to each other. The longitudinal body preferably extends from the center of the latter and thus the drain  2  is also generally T-shaped. 
   The outline of the drain is defined by the edges of the transverse bar  50  and of the longitudinal body  60  and comprises a front edge  54  comprising a central convex portion of the transverse bar  50  then continuing rectilinearly as far as the rounded ends  53  of the bar. The outline then follows the lateral edges  55  on the other side of each of the arms and then follows the lateral edges  64  of the longitudinal body  60  which converge towards a small rounded end  63  at the rear end of the longitudinal body  60 . 
   According to a third embodiment, the drain comprises an anterior face, not illustrated in  FIG. 6 , which is substantially planar and thus without relief portions. The same applies to the posterior surface of the longitudinal body  60  and of the median zone  71  of the transverse bar  50 . 
   According to a preferred embodiment, the posterior face  30  of the drain  2  comprises, on each side of the median zone  71 , a projection  52 , of generally semi-frustoconical form of which the apex is situated at the rounded end  53  of the respective arms. 
   The median zone  71  located between the projections  52  is thus in the same plane as the posterior surface  70  of the longitudinal body  60 . 
   An opening  62 , preferably circular, is formed at approximately two-thirds of the distance between the edge  52  and the rounded end  63  and is located on the longitudinal axis of the body. 
   Similarly, due to the high water content of the 38% polyHEMA or of the hydrophilic acrylic, the aqueous humor may also pass via the drain itself to the uveoscleral circulatory system. Finally, as in the first two embodiments, by virtue of the fact that the drain is non-resorbable and hydrophilic, a permanent space is produced around the body of the drain, despite the inevitable scarring between the scleral bed and the superficial scleral flap. 
   In the hydrated state, the width of the transverse bar  50  between its opposite ends  53  is preferably 3.5 to 4.5 mm and more particularly of the order of 3.5 mm. The length of each of the arms of the transverse bar is of the order of 1 mm. The height of the transverse bar defined between the opposite edges is of the order of 0.2 to 0.4 mm and preferably approximately 0.25 mm. Similarly, the total height of the drain is preferably between 3 and 4 mm, and more particularly 3.5 mm. The width of the drain adjacent the slit made in Schlemm&#39;s canal is preferably between 1.3 and 1.8 mm and more particularly of the order of 1.5 mm, that is to say of the order of 0.1 mm less than the width of the slit. 
   The thickness of the drain is of the order of 0.1 mm except at the projections where it is of the order of 0.30 mm. 
   The glaucoma drain of this third embodiment may thus be implanted in the same manner as in accordance with the first embodiment. 
   Whatever the form of the glaucoma drain produced for example from 38% polyHEMA or from hydrophilic acrylic, it may be manufactured according to usual processes in the field of intraocular implants. Preferably, the drain is lathe cut. 
   Once produced and sterilized, the drain is packaged in a pouch or vial containing an isotonic solution such as 0.9% NaCl. The drain may be mounted into a support (not shown) so that it can be manipulated more easily. 
   Naturally, the present invention is not limited to the form of the embodiment described and represented, but covers any variant forms. Although the T-shaped form of each of the illustrated embodiments is preferred for the two applications described, other configurations may be adopted. Similarly, other non-resorbable and hydrophilic materials may be used to produce flexible intraocular implants.