Abstract:
An intraocular lens to be implanted into the capsular bag after ablation of the crystalline lens includes a central optical portion and a haptic portion including haptic members arranged on the periphery of the optical part and for positioning the intraocular lens in the capsular bag. On the one hand, the posterior surface of the optical portion includes a sharp ridge at the peripheral edge and, on the other hand, the posterior surface of the haptic members includes a proximal area in the vicinity of the peripheral edge of the optical portion, each proximal area including at least one tooth extending substantially along the entire width of each haptic member, the tooth or teeth having a sharp edge that becomes serrated in the posterior capsule in order to limit the migration of the epithelial cells of the haptic members towards the optical portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to intraocular lenses or implants designed to be implanted in the capsular sac after the ablation of the crystalline lens suffering from cataract. 
     2. Description of the Related Art 
     The ablation of the crystalline lens is most frequently carried out by capsulotomy of the leaf or anterior capsule followed by a phacoemulsification of the crystalline lens and the cleaning of the site and notably the capsular sac in order to eliminate the epithelial cells. However, Elschnig pearls that form from the germinative cells subsist on the equator of the capsular sac after the surgical operation. These cells migrate along the posterior capsule and cause the opacification of the posterior capsule. Because of the opacification of the posterior capsule, also called second cataract, in the three years following the ablation of the crystalline lens and the implantation of an intraocular lens, approximately thirty per cent of patients need a new operation, namely a capsulotomy of the posterior capsule by Nd:YAG laser, with the disadvantage of the creation of communication between the anterior and posterior segments of the eye. Moreover, the opacification of the posterior capsule (PCO) forms the most common complication in cataract surgery. 
     In general, the intraocular lens comprises an optic portion which provides the optic and notably refractive correction and a haptic portion comprising at least one haptic element and in practice at least two haptic elements which rest in the equatorial zone of the capsular sac, and even the ciliary sulcus, and ensure the positioning of the optic axis of the optic portion substantially coinciding with the optic axis of the eye and of the pupil. When the haptic elements are angled anteriorly, the optic portion is in contact with the posterior capsule. 
     In a study by Nagata et al. “Optic sharp edge or convexity: comparison of effect on posterior capsular opacification”, Jpn J Opthalmol., Vol. 40; 397-402, 1996, they found that a rounded edge of the posterior face of the optic allows the invasion of the epithelial cells behind the optic while a sharp edge, also called “square” edge, is effective in reducing the opacification of the posterior capsule. In the article “Posterior capsule opacification” by Nishi, J Cataract Refract Surg—Vol. 25, January 1999, the author confirmed that the sharp or square edge of an optic produces a “discontinuity or a sharp bend” in the posterior capsule which is associated with a reduced incidence of opacification of the posterior capsule. 
     Square-edged intraocular lenses, also called anti-PCO intraocular lenses, currently exist in two types. On the one hand, there are three-part intraocular lenses comprising an optic portion, for example made of flexible material such as an acrylic polymer, and two haptic elements made of polypropylene or another rigid material anchored in the periphery of the optic portion, and, on the other hand, there are intraocular lenses made in one piece and of flexible material or a combination of rigid and flexible material. 
     In an article entitled “Evaluation of lens epithelial cell migration in vivo at the haptic-optic junction of a one-piece hydrophobic acrylic intraocular lens”, Nixon and Apple report the much higher frequency of opacification of the posterior capsule requiring a capsulotomy with the intraocular lenses in one part made of acrylic compared with those with intraocular lenses in three parts comprising an optic made of acrylic and fitted haptic elements made of polypropylene. One of the problems with one-piece intraocular lenses reported by these authors is the absence of an effective square or sharp edge at the junction of the posterior face of the optic with the posterior face of the haptic elements. The authors recommend a sharp or square edge of 360° on the posterior face of the optic. 
     It has also been found that the migration of the epithelial cells is preferably carried out by means of the haptic elements. Specifically, during the capsular symphysis, that is to say in the weeks and months following the implantation of the intraocular lens, the leaves of the sac come together at the haptics and the periphery of the optic, trapping the epithelial cells in zones located essentially at the haptic elements of the implant. These cells then migrate toward the centre of the optic following an axial offset between the optic and the haptic elements. 
     Also known is document WO 01/03610 which describes an intraocular lens made in one piece of rigid material such as PMMA, or of a hydrophobic or hydrophilic flexible material and notably silicone, the acrylic polymers, and even polyHEMA, the haptic portion of which makes an angle of between 5° and 12° directed toward the anterior face, a zone of connection between the optic portion and the haptic elements, a radial extension of the connection zone of which the posterior face is placed on the spherical cap of the posterior face of the optic portion and a step made by an axial offset between the posterior face of the optic portion and the connection zone of the optic element. 
     But, with such a geometry, the posterior face of the haptic elements cannot be in the continuity of the posterior face of the optic but is necessarily axially offset toward the front. 
     Also known is document WO 03/039409 which describes an intraocular lens in one piece or several pieces made of a flexible or rigid material in which the periphery of the optic portion comprises two or three steps from the periphery of the posterior face of the optic portion, in which each of these steps forms a sharp or square edge designed to prevent the migration of the epithelial cells behind the optic portion. 
     Such a geometry does not provide a solution to the problem of migration at the junction between the haptic elements and the optic portion when the lens is made in a single piece. Similarly, the formation of the plurality of steps in the cylindrical periphery of the optic portion cannot provide a good contact with the posterior capsule in order to form an effective barrier against the progression of the epithelial cells between the posterior face of the optic portion and the posterior capsule. 
     Finally, document WO 2005/055875 is known in which is described an intraocular lens for implantation into the capsular sac, comprising an optic portion and a haptic portion, the posterior face of the optic portion having a sharp ridge on the peripheral edge and the posterior face of the haptic elements comprising at least one tooth. However, the sharp ridge on the peripheral edge is interrupted at the junction of the haptic and optic elements. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to improve or eliminate the aforementioned drawbacks of anti-PCO lenses. 
     According to the invention, an intraocular lens is provided for implantation in the capsular sac after ablation of the crystalline lens, comprising a central optic portion and a haptic portion comprising haptic elements arranged on the periphery of the optic portion in order to position the intraocular lens in the capsular sac, the intraocular lens being characterized in that, on the one hand, the posterior face of the optic portion has a sharp ridge on the peripheral edge, and, on the other hand, the posterior face of the haptic elements comprises a proximal zone close to the peripheral edge of the optic portion, each proximal zone comprising at least one tooth extending over substantially the whole width of each haptic element, the tooth or teeth having a sharp edge designed to indent itself into the posterior capsule in order to limit the migration of the epithelial cells of the haptic elements toward the optic portion. 
     Thus, the intraocular lens of the present invention comprises, at the junction of the haptic and optic elements, at least two anti-PCO barriers, the first being defined by the sharp ridge of the peripheral edge at the junction of the haptic and optic elements, and the second defined by the tooth or teeth on the posterior surface of the haptic elements. 
     Such an intraocular lens may also comprise one or more of the following features: 
     Thus, the proximal zone may comprise a network of teeth of at least two parallel teeth. 
     Thus, the sharp ridge of the tooth or teeth of each haptic element is in continuity with the curvature of the posterior surface of the haptic element concerned. 
     Thus, the radial section of the teeth of each haptic element may have substantially the same configuration and the same dimensions. 
     Thus, the sharp edge of each tooth of each haptic element may be substantially parallel to the sharp ridge of the peripheral edge of the optic portion and may be placed on a surface slightly offset relative to the posterior face of the optic portion by the height of the sharp ridge at the peripheral edge of the optic. 
     Thus, the sharp ridge of the tooth or teeth may be defined at the intersection of an outer slope at an acute angle relative to the posterior surface of the haptic element and an inner slope substantially perpendicular to the posterior surface of the haptic element. 
     Thus, the height of each tooth may be between 0.05 mm and 0.1 mm approximately. 
     Thus, the sharp ridges of the teeth may be at the intersection of two inclined slopes forming an angle of between 40° and 70°. 
     Thus, the grooves between the successive teeth of a network of teeth may have a radial section in the shape of a U or of a V, and the sharp ridges may be defined at the intersection of the posterior surface of the haptic element concerned and the free edge of the grooves. 
     Thus, the tooth or teeth may define a sharp ridge slightly protruding relative to the posterior surface of the haptic element concerned, or in continuity therewith. 
     Thus, the tooth or teeth of a network of teeth on the posterior surface of the haptic element concerned may have different radial widths. 
     Thus, the tooth or teeth on the posterior surface of the haptic element concerned may comprise a slope inclined both posteriorly and toward the outer periphery of the optic portion. 
     Thus, the tooth or teeth of each haptic element may extend over a radial width of 0.5 to 0.8 mm. 
     Thus, the tooth or teeth of each haptic element concerned may extend in a widened proximal zone of the haptic element of generally triangular shape between the peripheral edge of the optic portion and the opposite lateral edges of the haptic element concerned. 
     Thus, the posterior surface of the haptic elements may be slightly offset relative to the spherical posterior surface of the optic portion by the height of the sharp ridge at the peripheral edge. 
     Thus, the intraocular lens may be mainly or entirely made of a hydrophobic or hydrophilic flexible acrylic polymer. 
     Other features and advantages of the invention will also become apparent in the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       In the appended drawings, given as nonlimiting examples: 
         FIG. 1  is a view of the posterior face of an intraocular lens of a first embodiment of the invention; 
         FIG. 2  is a view in elevation of the intraocular lens of the first embodiment; 
         FIG. 3  is an axial section of an eye after ablation of the crystalline lens and the implantation of the intraocular lens of the first embodiment; 
         FIG. 4  is an enlarged detail view of the encircled zone of  FIG. 3  to illustrate the contact of the posterior surface of the optic and of one of the haptic elements with the posterior capsule of the capsular sac; 
         FIG. 5  is a view of the posterior face of an intraocular lens of a second embodiment of the invention; 
         FIG. 6  is a view in elevation of the intraocular lens of the second embodiment; 
         FIG. 7  is a view of the posterior face of an intraocular lens of a third embodiment of the invention; 
         FIG. 8  is a view in elevation of the intraocular lens of the third embodiment; 
         FIG. 9  is an enlarged detail view to illustrate the network of teeth of one of the haptic elements according to another embodiment; 
         FIG. 10  is an enlarged detail view to illustrate the network of teeth of one of the haptic elements according to another embodiment; 
         FIG. 11  is an enlarged detail view to illustrate the network of teeth of one of the haptic elements according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The first embodiment of an intraocular lens will be described with reference to  FIGS. 1 to 4 . The intraocular lens  10  comprises an optic or optic portion  20  and a haptic portion  30 . This intraocular lens  10  is preferably made in one piece by machining in flexible transparent and biocompatible material such as acrylic polymer, polyHEMA, silicone preferably in hydrophobic flexible material, notably a hydrophobic acrylic polymer. However, such a lens may comprise one or more zones of rigid material, for example by the use of the “Flexizone” technology described in document EP 1 003 446. 
     The optic portion  20  forms the central portion of the intraocular lens  10  and has a circular contour. The curvature of the anterior and posterior faces  20  determine the notably refractive correction in substitution of the excised crystalline lens. The anterior face  21  and/or the posterior face  22  may be spherical and/or aspherical. The radius of curvature of the spherical posterior face is preferably constant irrespective of the curvature of the anterior face of the optic portion. In this case, it is the curvature of the anterior face that may be spherical or aspherical, the radius or radii of curvature conforming to the correction chosen by the surgeon in order to satisfy the desiderata of the patient. The peripheral edge  23  of the optic portion has a cylindrical shape, or is slightly frustoconical tapering off anteriorly, as illustrated. The intersection of this peripheral edge  23  and the posterior face  22  of the optic portion  20  forms a sharp ridge  24  also called a square edge or sharp edge. The angle between the peripheral edge  23  and the posterior face  22  is preferably between 80° and 100°. The intersection of the peripheral edge  23  and the anterior face  21  of the optic portion  20  may be sharp or rounded. 
     The haptic portion  30  comprises at least two haptic elements. As illustrated, the haptic portion  30  comprises two haptic elements  31 . These haptic elements  31 , as illustrated, form open arches  31 ,  32 , in the various embodiments of the present application, or if necessary closed arches, or even “flat” haptic elements, which may have holes in them. Each arch is preferably the mirror image of the other about a diameter of the optic portion  20 . These arches, as illustrated, are generally C-shaped or J-shaped, with a proximal zone  32  close to the optic portion  20  and which in practice forms the zone of connection with the haptic portion. The circumferential extent of the proximal zone at the junction with the optic portion is widened and relatively large, for example at an angle of 40° to 80° and preferably from 45° to 60° from the periphery of the optic portion  20  as illustrated. The proximal zone or portion  32  of each haptic element  31  has a generally triangular shape, from the junction with the optic portion  20  extending generally radially outward from the zone of connection with the optic portion. The distal portion  34  of each haptic element  31  has a relatively uniform width and terminates in a rounded free end  37  which may if necessary be widened relative to the width of the rest of the distal portion. The width of the distal portion  34  of the haptic element  31  is preferably of the order of 0.30 to 0.60 mm and the measured thickness, parallel to the axis of the optic, of the order of 0.30 to 0.60 mm. 
     According to the present invention, the posterior face of the proximal portion  32  of each haptic element  31  comprises at least one tooth and preferably a plurality or network of teeth  35  that are substantially parallel and radially spaced from one another. These teeth  35  form as many individual barriers to the migration of the epithelial cells toward the periphery of the posterior face  22  of the optic portion  20  and between them grooves  36  are formed that are capable of trapping epithelial cells which have been able to pass through the barrier formed by the tooth  35  which is just on the outside of the groove. 
     Preferably, the teeth  35  extend circumferentially between the lateral—more or less radial—opposite and respectively concave and convex edges of the proximal portion  32  of the haptic element  31  concerned. As illustrated, these teeth  35  extend over arcs of a circle parallel to the peripheral circular edge  23  of the optic portion and therefore concentric with the latter. The radial distance between the respective teeth and therefore the width of the grooves between them is from 0.1 mm to 0.3 mm approximately. In this first embodiment, the radial distance that separates the ridge of the first tooth from the ridge of the peripheral edge  23  of the posterior face  22  of the optic portion  20  is equal to the distance between the successive teeth  35 . 
     In the first embodiment, there are two teeth  35  and three grooves  36 , respectively between the peripheral edge  23  of the posterior face  22  of the optic portion  20  and the first tooth  35 , between the first and second tooth  35 , and beyond this second tooth  35 . The proximal portion  32  of the haptic element  31  may comprise, over all or part of its radial extent, at least one tooth, and preferably a network or a plurality of teeth, and in practice a maximum of five teeth. 
     In this embodiment, the network of teeth has a “sawtooth” shape. Each tooth  35  comprises an inner slope  35 A inclined anteriorly at an angle of approximately 40° to 70° and an outer slope  35 B substantially parallel to the axis of the optic portion  20  and perpendicular to the posterior surface of the distal portion of the haptic element. The outer slope  35 B of the second tooth is extended by a slope parallel to the inner slope  35 A of the first tooth and which joins the posterior face of the proximal portion  32  of the haptic element  31 . 
     In this first embodiment, the anterior face  38  of the proximal portion  32  of the haptic element  31  is very slightly tapered toward the peripheral edge  24  of the optic portion so that the thickness of the haptic element  31  in the proximal portion  32  is almost constant. 
     As illustrated in  FIG. 1 , the direction of the curvature of the haptic elements  31  is counterclockwise. Evidently the direction of the curvature of the haptic elements may be the opposite direction. As illustrated, the terminal end  37  of each haptic element  31  is on the extension of one and the same diameter of the optic portion  20 . But the circumferential extent of the distal portion  34  may be greater or lesser. 
     Such an intraocular lens may be implanted by means of a surgical tweezer or preferably by means of a cassette injector as described in document EP 1 453 440. In the case of the injection of an intraocular lens made of hydrophobic acrylic, the intraocular lens will be sterilized in its cassette by exposure to ethylene oxide gas, by gamma radiation, or by hydrogen peroxide plasma sterilization. 
     The radius of the spherical curvature of the posterior face  22  of the optic portion  20  and the haptic portion  31  ensures, after the post-operative retraction of the capsular bag or sac, an intimate contact between the posterior face  22  of the intraocular lens  10  and a posterior capsule of the capsular bag or sac, and more particularly at the peripheral edge  34  of the optic portion  20  and at the network of teeth  35 . The anterior angulation of the haptic elements  31  (see  FIG. 2 ) produces an axial pressure force at the sharp ridge  24  of the peripheral edge  23  and of the network of teeth  35  sufficient to produce a slight indentation of the sharp ridge of the teeth and/or the sharp ridge of the peripheral edge in the tissue of the posterior capsule (see  FIG. 4 ) and hence in principle three levels of effective barriers against the migration of the epithelial cells. 
     The intraocular lens  110  of the second embodiment comprises most of the features of the first embodiment. The same elements or the elements having the same functions are designated by the same reference numbers increased by 100. Only the modified features of the second embodiment will be described. 
     The second embodiment illustrated in  FIGS. 5 and 6  has essentially two differences relative to the first embodiment. The first difference is the shape of the arches that are formed by the haptic elements  131  of the haptic portion  130  but that is still C-shaped or J-shaped. The proximal zone or portion  132  between the haptic elements  131  has a smaller circumferential extent, from 50° to 60° approximately. Moreover, the concave edge of the proximal portion  132  is virtually rectilinear, thus accentuating the triangular shape of the proximal portion when the lens is seen from the front. Then the distal portion  134  of the haptic elements  131  is less curved. Similarly, the free end  137  of each haptic element  131  comprises a rounded shape the width of which is greater than the width of the rest of the distal portion  134  of the haptic element  131 . Such a haptic configuration has the advantage of allowing the rectilinear lengthening of the haptic element in order to facilitate the injection of the “leading” arch. Finally, a notch  138  is formed on the concave edge of the distal portion  134 . 
     The intraocular lens  210  of the second embodiment comprises most of the features of the first embodiment. The same elements or the elements having the same functions are designated by the same reference numbers increased by 200. Only the modified features of the third embodiment will be described. 
     The shape and general curvature of the C-shaped or J-shaped arches formed by the haptic elements  231  of the haptic portions  230  of the third embodiment, illustrated in  FIGS. 8 and 9 , are similar to those of the second embodiment. But instead of a half-way notch on the concave edge of the distal portion of the haptic elements  231 , in the third embodiment, a deeper notch  238  is present on the convex edge of the haptic elements  231  just beyond the proximal portion  232  of the haptic elements  231 . 
     The production, insertion and implantation and the barrier effect of the square peripheral edge of the optic portion and the network of teeth of the proximal portion of the haptic elements after the retraction of the capsular sac of such an intraocular lens according to the second or third embodiment are substantially the same as those of the first embodiment. 
       FIGS. 9 to 11  represent variants of the network of teeth capable of being incorporated into the intraocular lenses in such an anti-PCO intraocular lens and notably that of the first, second and third embodiments. 
     Unlike the first three embodiments in which the thickness of the proximal portion of the haptic elements is substantially uniform, that of the variants of  FIGS. 9 to 11  comprises a reduction in thickness toward the peripheral edge of the optic portion, by virtue of the inclination of the anterior surface  338 ,  438 ,  538  of the haptic element in the proximal zone so that the axial thickness is at the minimum close to the peripheral edge. 
     In the variant of  FIG. 9 , the radial width of the inner slope  336  of the first tooth  335  is at least twice the length of the inner slope  336 A of the second tooth. 
     In the variant of  FIG. 10 , the sharp ridges are at the intersection of the posterior surface of the proximal portion of the haptic element and the free end of the U-shaped grooves  436 . In such a variant, there is one tooth or sharp ridge  435  on either side of a thin segment which separates the free edges of the successive grooves  436 . 
     The variant of  FIG. 11  comprises a network of teeth similar to that of the embodiments of  FIGS. 1 to 8 , but in which the anterior surface  538  of the haptic element in the proximal zone is inclined toward the peripheral edge of the optic, as in the variants of  FIGS. 9 and 10 . 
     Naturally, many modifications may be made to the exemplary embodiment described above without departing from the context of the invention.