Abstract:
An intraocular implant for use in a surgical procedure such as a cataract operation, or in a refractive-lens exchange surgery procedure, has a main portion and a peripheral portion peripheral to the main portion. The main portion is plate-like in shape and may be a lens or a plug for closing an aperture in the capsule of the eye. The implant has two or more lugs extending from the peripheral portion in a direction substantially perpendicular to a plane of the main portion. The lugs extend either from haptics, which protrude from the main portion, or from a short extension of the edge of the main portion. A method for fixing the implant into the eye involves making two or more voids in the capsule wall, offering up the implant to the capsule, so that the lugs lie adjacent to the voids, and inserting the lugs into the voids.

Description:
FIELD OF THE INVENTION 
     The invention relates to an intraocular implant, and in particular to an intraocular implant for use in cataract operations or refractive crystalline lens extraction operations. The invention also relates to a method for fixing such an intraocular implant into an eye. 
     BACKGROUND OF THE INVENTION 
     The cataract condition is a well known eye ailment, which these days is easily treatable through surgery. The condition involves an opacification, yellowing or clouding of the natural crystalline lens (see  FIG. 1 ), which is situated just behind the iris and serves to focus the incoming image onto the retina at the back of the eye. 
     The surgical procedure involves the removal of the opaque lens and its substitution by an artificial lens having the required focusing effect. 
     One way of achieving this is described in U.S. Pat. No. 3,925,825.  FIGS. 2 and 3  correspond to  FIGS. 1 and 2  of this patent, and show the placing of a lens  10  anterior to the iris  12 . The lens is held in place against the iris by a haptic section  14 . The haptic section  14  consists of a series of bent wire loops  16 , which are attached to a circular wire frame  18 . The lens  10  has a flat circumferential face  20  and the lens is held within the frame  18  by inserting the lens inside the frame  18  and closing the legs  22  of the frame so that the frame  18  closes tightly against the lens face  20 . Once the legs  22  have been brought together, their ends are kept together via a terminal part  24 . 
     One way of extracting the opaque natural lens—a process known as extra-capsular extraction—will now be described. Reference is first made to US 2003/0130732,  FIG. 1  of which corresponds to  FIG. 4  of the present application. The lens  30  is accommodated within a so-called capsule (also sometimes referred to as a “capsular bag”, or simply “bag”), which is shown as item  32  in  FIG. 4 . To remove the opaque lens, an opening (a so-called “capsulotomy”) is made in the anterior part  34  of the capsule  32  manually by a surgeon or by a pulsed laser and the lens  30  is removed through the opening. 
     To facilitate the removal of the opaque or cloudy lens, the lens is first emulsified by the phacoemulsification method or by a pulsed laser. Phacoemsulification involves making a small incision in the cornea and introducing a very thin needle through the incision, which is then brought into contact with the lens through the capsulotomy. The needle is caused to vibrate at an ultrasonic frequency by the use of a magnetostrictive driver. The ultrasonic vibrations of the needle soften the lens and emulsify it. The emulsified parts can then be aspirated out of the capsule through the incision. Finally, the incision is widened sufficiently to introduce the substitute artificial lens into the capsule. A pulsed laser can be used to create an opening in the capsule, by photoablating capsular tissue along a predetermined boundary, which can be circular or elliptical if desired. 
     Like the lens of  FIG. 2 , the lens in the extra-capsular method is conventionally held within the capsule by the use of haptics. One example of this is shown in U.S. Pat. No. 5,376,115.  FIGS. 5 and 6  are an extract from this patent, in which the artificial lens  36  with its haptics  38  is introduced through the iris and into the capsule  40  via the capsulotomy ( FIG. 5 ) and finally brought to bear against the inside posterior surface of the capsule ( FIG. 6 ). The haptics  38  are used to center the lens and secure it in place inside the capsule. 
     SUMMARY OF THE INVENTION 
     One problem associated with the known capsular insert technique is that it is difficult to centre the lens accurately in the X-Y plane of the eye. (The X-Y-Z co-ordinates are shown in  FIGS. 7 and 8 .) This is the case, even though the haptics are supposed to centre the lens as close to the optical axis of the eye as possible. The reason for this is that the pupil of the eye, which is the opening of the iris, is not necessarily centered with respect to the capsule. Hence the lens can be centered with respect to the capsule, but not with respect to the pupil. 
     It is also difficult to ensure that the lens has the desired placement in the rotational direction in the X-Y plane. A third problem is that, due to the presence of the haptics, the known technique requires a fairly large incision in the eye in order to be able to introduce the implant into the eye, whereas it is always desirable to be able to minimize the degree of intervention, including the size of the incision. 
     A further drawback is the difficulty of accurately defining the location of the lens in the Z-direction. This can lead to difficulties in defining the required optical power of the lens. 
     It is an aim of the intraocular implant according to the present invention to mitigate drawbacks associated with the known implant techniques. 
     The present invention provides an intraocular implant for placement in the eye, the implant comprising a main portion, which is a lamina, and a peripheral portion peripheral to the main portion, the implant having at least two lugs extending from the peripheral portion in a direction substantially perpendicular to a plane of the lamina, the lugs being for engagement with corresponding voids provided in a capsule of the eye. 
     The peripheral portion may comprise at least two haptics extending from the main portion, the haptics comprising respective lugs extending from the haptics in said direction substantially perpendicular to the plane of the lamina. 
     The peripheral portion may comprise a short extension of the main portion over the entire periphery of the main portion, the extension of the main portion comprising the at least two lugs. This configuration is potentially more compact than the haptic-based configuration. According to one example embodiment, the lugs are substantially equidistantly spaced around the peripheral portion. This allows for greater stability of attachment of the implant to the capsule. 
     The at least two lugs may each comprise a neck portion, which extends from the peripheral portion in the direction substantially perpendicular to the plane of the lamina, and a head portion extending from the neck portion. The head portion may be mushroom-shaped or otherwise larger than the neck portion, which allows for easier and more secure attachment of the implant to the capsule. 
     The neck portion may have a length, in the direction substantially perpendicular to the plane of the lamina, approximately equal to the thickness of a wall of the capsule. This length may be in a range 30 to 50 micrometers for example. In addition, the neck portion may have a diameter in a range 100 to 500 micrometers for example. 
     The implant may take the form of a lens, in which case the main portion of the implant will comprise the optic of the lens. Alternatively, the implant may be a plug for occluding an opening in the capsule of the eye. The plug may have no optical power and may or may not be opaque. 
     The present invention also provides a method for fixing the intraocular implant into an eye, the method comprising: forming voids within the capsule of the eye, the number of voids corresponding to the number of lugs of the implant; orienting the implant proximate to the capsule, so that the lugs face toward respective voids, and inserting the lugs into the voids, thereby securing the implant to the capsule. 
     In this method, the at least two lugs may each comprise a neck portion, which extends from the peripheral portion in the direction substantially perpendicular to the plane of the lamina, and a head portion extending from the neck portion, and wherein the lugs are inserted, head portion first, into the voids, the head portion being such as to discourage the implant from coming away from the capsule. 
     Before the orienting step, there may be the step of surgically removing the natural crystalline lens material of the eye, and, when the capsule is evacuated of the natural crystalline lens material, fixing the implant onto the capsule from either inside or outside the capsule. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example only, with reference to the drawings, in which: 
         FIG. 1  is a sectional view of the human eye; 
         FIG. 2  is a part-side and part-sectional view of a human eye with an artificial lens substituted for the original lens in accordance with a known method; 
         FIG. 3  shows a haptic arrangement used in the known method of  FIG. 2 ; 
         FIG. 4  is a sectional view of a human eye showing the natural lens in its capsule; 
         FIGS. 5 and 6  are sectional views showing two stages in a known lens replacement method employing extra-capsular extraction; 
         FIGS. 7 and 8  are front and top views, respectively, of an intraocular implant in accordance with an example embodiment of the invention; 
         FIGS. 9( a )-9( e )  are enlarged views of different versions of the lug shown in  FIGS. 7 and 8 ; 
         FIGS. 10 and 11  are front and top views, respectively, of an intraocular implant in accordance with another example embodiment of the invention; 
         FIGS. 12-19  are various examples of lenses in place in a lens capsule; and 
         FIG. 20  shows two examples of a plug-type implant. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 7 and 8  show an intraocular lens comprising the lens proper (the “optic”)  50  and a pair of haptics  52 . The optic is a lamina, i.e. roughly plate-shaped, so that its diameter (assuming a circular profile) is much greater than its thickness, especially at the edges. Extending from each haptic at a point part-way along its length is a lug  54 . The lugs are configured in this example as shown in, e.g.,  FIG. 9( a )  and have a neck  56  and a head  58  and are of one piece with the respective haptics. The lugs extend in a direction substantially perpendicular to the plane  53  of the lamina. In one example of its use, the lens is inserted into the capsule of the eye through a capsulotomy previous made in the eye and is secured to the capsule by inserting each lug through a void made in the capsule by suitable means. In this respect convenient use can be made of the modern femtosecond pulsed laser technique, which enables voids of very accurate size and location to be made in the capsule by laser-pulse photoablation along a predetermined boundary. This means that the lens can be produced as a standard item with the lugs  54  disposed at a standard distance apart from each other and from the optical centre of the optic, leaving it up to the surgeon to form voids of the correct location and size in the capsule to suit this standard distance. 
     The head  58  of the lugs is preferably, but not necessarily, mushroom-shaped (see  FIG. 9( a ) ), which facilitates the insertion of the lug into the void made in the capsule. By contrast the surface  60  of the head behind the mushroom surface is desirably linear, to discourage the lug from coming out of the void of its own accord. Thus, the void will normally be a through-hole of a diameter approximately equal to that of the neck of the lug. In addition, the neck of the lug will normally be of a length approximately the same as, but preferably somewhat greater than the anticipated thickness of the capsule wall (which is approximately 20 micrometers). A typical range of values for the length of the neck is 30 to 50 micrometers and for the diameter of the neck is 100 to 500 micrometers. 
     The profile of the lugs may be other than mushroom-shaped, provided it allows relatively easy insertion of the lugs into the voids in the capsule wall. Thus, the lug may have a “T”-shaped cross-section, as shown in  FIG. 9( b ) . A preferred variant of this “T” profile is  FIG. 9( c ) , in which the outer edge is chamfered, making it easier to insert. Also, while the inclusion of a head is to be preferred, for the reason given in the preceding paragraph, it is not absolutely essential. Thus, the invention also envisages the use of a lug as shown in  FIG. 9( d )  or  FIG. 9( e ) . In  FIG. 9( d )  the lug consists of just the neck, which has a square top. A variant of this, similar to that shown in  FIG. 9( c ) , is a rounded-top version illustrated in  FIG. 9( e ) . Where the lug is headless, it may be expedient to ensure a fairly tight fit between the lug and the capsule void, in order to discourage migration of the implant away from the capsule. 
     As regards the profile of the lugs in plan view (view orthogonal to the sectional view of  FIG. 9 ), this is preferably circular, though other profiles may also be suitable. 
     A second embodiment of the implant in accordance with the invention is illustrated in  FIGS. 10 and 11 . 
     Here the implant has no haptics, but consists of the optic  70  plus a peripheral section  72 , which is a simple extension of the edge of the optic  70 . The radial width of the extension will be at least sufficient to accommodate the lugs and to ensure that the voids made in the capsule are reasonably remote from the lip of the capsulotomy. Four lugs  74  protrude from, and are of one piece with, the peripheral section, being substantially equidistantly spaced around the peripheral section. The lugs  74  are configured as in the first embodiment (see  FIG. 9 ). 
     This implant is smaller than that of the first embodiment, since no haptics are present. This means that the incision to be made in the eye, in order to introduce the implant into the eye, can be made smaller, with a smaller wound and leading to a faster recovery of the patient and less induced astigmatism. 
     When the implant is located adjacent to the inside of a capsulotomy made in the anterior part of the capsule (an “anterior capsulotomy”)—this location is called the “bag fixated” location—the lugs will face toward the front of the eye. This situation applies to the first embodiment, since it assumes the use of haptics, and also to the second embodiment. In addition the lugs can be placed on the posterior side of the device and be fixated in the bag using posterior facing lugs and voids in the posterior capsule. There may or may not be a posterior capsulotomy separate from the voids to receive the lugs. In addition, where the implant of the second embodiment is located adjacent to the outside of the anterior capsulotomy (the “sulcus fixated” location), the lugs will be facing toward the back of the eye. The reverse will apply where the implant is located adjacent the inside or outside of a posterior capsulotomy. 
     Examples of the above-described first and second embodiments are shown in  FIGS. 12-19 . 
       FIG. 12  shows a side view of a lens without haptics located within a capsular bag. The lugs  80  are anterior-facing, i.e. facing toward the front of the eye, and are engaged with holes  82  created in the anterior wall of the bag  84 . An anterior capsulotomy  86  can also be seen.  FIG. 13  shows a front view of this arrangement, though with a somewhat wider capsulotomy  86  than that shown in  FIG. 12 . 
     A similar configuration, but involving a lens with haptics, is shown in  FIGS. 14 and 15 . The lens itself is shown in  FIG. 14 , while the lens in the bag is shown in  FIG. 15 . This time the lugs  90  are situated further away from the centre of the lens  92  and therefore engage with holes  94  located further away from the anterior capsulotomy  96 . 
       FIG. 16  depicts a side view of a lens  100  with haptics  102  and posterior-facing lugs  104 , which engage with holes  106  made in the posterior wall  108  of the bag. Also shown is an anterior capsulotomy  110 . 
       FIGS. 17 and 18  are top and front views, respectively, of a lens  120  located in the capsular bag  122 , in which the lens has haptics  124  and posterior-facing lugs  126  inserted into posterior capsular voids. This time a capsulotomy  128 ,  130  has been made in both the anterior and posterior walls of the capsule. Incidentally,  FIG. 18  shows, for clarity, a copy of  FIG. 17 , but with reduced dimensions to align with the diameter of the capsular bag shown in  FIG. 18 . 
     Finally, an example of a hapticless lens  140  having posterior-facing lugs  142  engaging posterior voids is shown in  FIG. 19 . The capsular bag has an anterior capsulotomy  144 . 
     The use of the lugs in these two embodiments has the following advantages:
         the implant can be reliably and repeatedly placed at a desired position in the X-Y plane vis-à-vis the capsule;   the implant can be very securely attached to the capsule;   the implant can be fixed at a desired rotational orientation, which is required where the lens has an asymmetrical optic (e.g. where there is variable optical power in the lens or where there is a toric optic);   since the implant can be held firmly against the capsule by the lugs (via the mushroom head), the implant can be made to have a well defined placement in the Z-direction (see  FIG. 8 ), which enables a reliable definition of the optical power of the implant to be obtained.       

     Instead of using only one lens as an implant, it may be necessary to employ a multi-lens design. Examples of such a design are illustrated and discussed in US 2003/0130732 mentioned earlier, the contents of which are incorporated by reference. The multiple lens form a unit and are secured to the capsule via either anterior-facing or posterior-facing lugs. Alternatively, both anterior and posterior facing lugs may be provided on respective front and back lenses, these lugs engaging with voids made in the anterior and posterior walls of the lens capsule. 
     In another example embodiment of the invention, the implant is not a lens, but a plug, blank or bung. Such an implant is not required to have any refractive power, but serves merely to close a fenestration or other aperture in the capsule. An example of this is shown in  FIG. 20 . Indeed,  FIG. 20  shows two examples of different diameter, depending on the size of the fenestration to be closed. It can be seen that this implant is flat and therefore has no optical power. Furthermore, the lugs in this situation are not required to accurately establish the rotational position of the implant (which would be the case with an asymmetrical lens), but merely to secure the plug to the capsule. 
     The plug may or may not be opaque, depending on the location of the aperture being closed. 
     A specific example of a plug in use with a capsule is not shown in the drawings. However, a typical scenario is as shown in  FIG. 12 , in which the lens was replaced by a plug such as shown in  FIG. 20 . The lugs engage with holes in one wall of the bag and block off an opening or fenestration, which might be larger than or smaller than the capsulotomy shown as item  86  in  FIG. 12 . 
     Fenestrations that might be closed off using the plug are, for example, fenestrations introduced into the capsule in order to facilitate the entry of an instrument for evacuating the lens material. In this respect, femtosecond lasers are often used to cut the lens into very small cubes or slices, so that they can be evacuated through a small-bore instrument or cannula. The cannula can be introduced into the capsule through such a fenestration. In addition, the plug can be used to provide tectonic support, in order to keep compartments in the eye physically separate. It is also useful as a means of preventing silicone oil from moving forward into the anterior segment of the eye. The plug may also be used to close or block a capsulotomy to inhibit vitreous prolapse. 
     Although a total of two lugs are shown in some embodiments and four in others, there may be as many lugs as there are haptics in the embodiment having haptics (there may also be fewer lugs than haptics), and fewer than, or more than, four lugs in the second. A criterion for selecting the number of lugs is to ensure a secure fixing of the implant to the capsule. 
     Also, it should be appreciated that the haptics shown in the example embodiment are representative only, and may take many other shapes. 
     The lugs, though shown as being unitary with the haptics or the lens extension, may instead be separate items, which are attached by suitable means to the haptics or extension in order to allow the lens optic to move or flex for accommodating lens designs. For flexible extensions a common material is silicone. The lugs may be constructed from silicone or acrylic material, as is common with current intraocular lens implants as well as other materials. 
     Similarly, while the implant, apart from the haptics, has been shown in the drawings as being essentially circular in shape, it may take any shape corresponding to the capsule opening against which it is to be located. Thus, where the implant is a lens, it may be oval or elliptical in shape, for example, instead of circular. 
     Although the use of the implant of the present invention has been described in connection with cataract surgery, alternative uses are envisaged. Thus, the implant can be also be employed in surgical procedures for treating myopia, hyperopia, astigmatism or presbyopia (refractive lens exchange surgery) or used in procedures where the natural lens is left in place and an implant lens is also inserted. 
     The foregoing description has been given by way of example only and it will be appreciated by a person skilled in the art that modifications can be made without departing from the scope of the present invention.