Patent Publication Number: US-2007106379-A1

Title: Intraocular lens

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to an intraocular lens for implantation in the anterior chamber of an eye, in particular a human eye.  
      2. Background Art  
      Intraocular lenses for implantation in the anterior chamber of an eye have been known for a long time and are implanted in the human eye either after removing the natural lens as a replacement for said lens or in addition to the natural lens to correct defective vision. Intraocular lenses which are additionally implanted without removing the natural lens are also termed phaco intraocular lenses. In the development and application of intraocular lenses of this type, there is a constant need to improve the compatibility and the imaging characteristics of the implanted intraocular lenses.  
     SUMMARY OF THE INVENTION  
      The object of the invention is to provide an intraocular lens for implantation in the anterior chamber of an eye, which lens avoids post-operative complications and imaging defects in the eye.  
      This object is achieved by an intraocular lens for implantation in an eye, with an optic which consists of an optic material and has an optical axis, an anterior optic surface extending continuously and transversely to the optical axis, a posterior optic surface extending continuously and opposite the anterior optic surface, a peripheral surface extending between the optic surfaces and along the optical axis, a sharp-edged anterior optic edge defining the peripheral surface and the anterior optic surface, and a sharp-edged posterior optic edge defining the peripheral surface and the posterior optic surface, and with at least two haptics which are attached to the optic, consist of a haptic material and have in each case two haptic arms for attaching the intraocular lens to the iris. The core of the invention consists in the fact that the anterior and posterior optic edges are configured sharply as a transition between the optic surfaces and the peripheral surface and the peripheral surface extends substantially along the optical axis. This measure basically prevents imaging defects caused by the optic edges and the peripheral surface. As a result of the sharp-edged transition to the peripheral surface, the optic surfaces may be used over the entire surface, i.e. also in the peripheral region thereof. The optic may be attached to the iris of the eye in a simple and very compatible manner by the haptic arms.  
      Additional features and details of the invention are provided in the description of an embodiment with reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  an anterior view of an intraocular lens,  
       FIG. 2 a  side view of the intraocular lens of  FIG. 1 ,  
       FIG. 3 a  cross-section through the intraocular lens along the section line III-III in  FIG. 1 ,  
       FIG. 4  an enlarged detail of the intraocular lens of  FIG. 3 , and  
       FIG. 5 a  cross-section through the intraocular lens along the section line V-V in  FIG. 1  with a simplified illustration of the haptic arms. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      An intraocular lens  1  is composed of several parts and has a central optic  2  and haptics  3  attached thereto. The optic  2  has in the centre an optical axis  4  and a lens plane  5  extending through the optic  2  perpendicularly on the optical axis  4 .  
      The optic  2  comprises an anterior optic surface  6  facing, when implanted, the cornea of the eye and a posterior optic surface  7  facing the iris of the eye and opposing the anterior optic surface  6  relative to the lens plane  5 . The optic surfaces  6 ,  7  extend substantially transversely to the optical axis  4  and are constant, i.e. the optic surfaces  6 ,  7  do not have any Fresnel zones because of their constant path. The surfaces  6 ,  7  preferably run in a continuously curved manner. An annular peripheral surface  8  runs concentrically and parallel to the optical axis  4  and extends between the optic surfaces  6 ,  7 . The peripheral edge  8  is delimited by a circular anterior optic edge  9  in the direction of the anterior optic surface  6  and by a circular posterior optic edge  10  in the direction of the posterior optic surface  7 .  
      The anterior optic edge  9  is of a sharp configuration and extends along a partial arc of a circle with a radius R 1  of less than 100 μm, particularly less than 50 μm and in particular less than 10 μm. The posterior optic edge  10  is also of a sharp configuration and extends along a partial arc of a circle with a radius R 2  of less than 100 μm, particularly less than 50 μm and in particular less than 10 μm.  
      The anterior optic surface  6  is curved in convex manner relative to the lens plane  5  and has a radius of curvature R A  ranging from 3 mm to 90 mm, particularly from 4 mm to 80 mm and in particular from 5 mm to 70 mm. Alternatively, the anterior optic surface  6  may also be curved in concave manner relative to the lens plane  5  and may have a radius of curvature R A  within the aforementioned ranges. The posterior optic surface  7  is curved in concave manner relative to the lens plane  5  and has a radius of curvature R P  ranging from 4 mm to 20 mm, particularly from 6 mm to 16 mm and in particular from 8 mm to 12 mm.  
      The optic surfaces  6 ,  7  are configured in such a way that it is possible to describe in mathematical terms a wavefront deformation substantially with Zernike polynomials up to an order of 8, particularly up to an order of 6, and in particular up to an order of 4. Zernike polynomials are a qualitative and quantitative measure of the imaging defects of the optic  2 .  
      The optic  2  is produced in one piece from an optic material. Silicone, for example, which has a refractive index of approximately 1.43 is used as the optic material. Alternatively, a hydrophilic acrylate having a refractive index of 1.46 or a high-refractive optic material having a refractive index of greater than 1.5 may be used as the optic material.  
      The two haptics  3  attached to the optic  2  extend radially outwards and are positioned opposite one another relative to the optical axis  4 . Alternatively, it is also possible to provide a different number of haptics provided that they are distributed uniformly over the circumference of the optic. The haptics  3  are identical and are attached to the optic  2 , so that in the following only one haptic  3  will be described in detail.  
      The haptic  3 , formed in one piece, has two haptic arms  12  defining a nipping gap  11  and a haptic strap  13  connecting the haptic arms  12 . The haptic strap  13  comprises an attachment portion  15  accommodated in an optic recess  14  and completely surrounded by the optic material, and exposed connecting portions  16  positioned on attachment portion  15 . Said attachment portion  15  extends in the middle concentrically to the optical axis  4  and is angled off at the ends in such a way that it extends adjacently to the connecting portions  16  and extends radially outwards corresponding to said connecting portions  16 . The haptic strap  13  penetrates the peripheral surface  8 , considered circumferentially, at an angle α of approximately 90°. The haptic strap  13  extends substantially tangentially to and flush with the posterior optic surface  7  and extends up to an anterior haptic edge  17  and a posterior haptic edge  18 . Seen along the optical axis  5 , the connecting portions  16  enclose with the peripheral surface  8  an angle β adapted to the radius of curvature R P  of the posterior optic surface  7 . The anterior haptic edge  17  and the posterior haptic edge  18  extend substantially parallel to the peripheral surface  8 , the anterior haptic edge  17  being at a greater distance from the optical axis  4  than the posterior haptic edge  18  due to the inclined position of the haptic strap  13  relative to the lens plane  5 .  
      In the centre, the attachment portion  15  has a cross-section in the shape of a parallelogram, an upper and a lower side wall extending parallel to the peripheral surface  8 , as shown in  FIGS. 3 and 4 . In the region of the peripheral surface  8 , the cross-section of the attachment portion  15  increases in such a way that along the peripheral edge  8  a width B B  of the attachment portion  15  corresponds to a width B V  of the connecting portions  16 . Seen along the optical axis  4 , the connecting portions  16  have a depth T V  which is greater than a depth T B  of the attachment portion  15 , so that the connecting portions  16  form a projection  19  which extends in the direction of the posterior optic edge  10  and rests against the peripheral surface  8 , as shown in  FIG. 5 .  
      A coating  20  which is impermeable to light of the visible spectrum is positioned between the attachment portion  15  of the haptic strap  13  and the optic material. Said coating  20  has a thickness D of at least 0.5 μm, particularly at least 1 μm and in particular at least 5 μm. As an alternative to the coating, the surface of the attachment portion  15  may be roughened  
      Emanating from the anterior haptic edges  17  and the posterior haptic edges  18 , the haptic arms  12  extend parallel to the lens plane  5 . The haptic arms  12  extend, emanating from the haptic edges  17 ,  18 , initially radially outwards and then bend in such a way that they extend substantially parallel to the peripheral surface  8  and towards one another. At their free ends, the haptic arms  12  have end faces  21  which extend perpendicularly to the lens plane  5  and laterally define the nipping gap  11 .  
      To attach the intraocular lens  1  to the iris, the haptics  3  have on the end faces  21  an average surface roughness of at least 5 μm, particularly at least 10 μm and in particular at least 20 μm. The average surface roughness of the other haptic surfaces is less than 4 μm, particularly less than 3 μm and in particular less than 2.5 μm.  
      The peripheral surface  8  of the optic  2 , the connecting portions  16  of the haptic strap  13  and the haptic arms  12  substantially define a haptic recess  22 . This haptic recess  22  is connected to the nipping gap  11 .  
      The haptics  3  are formed in one piece from a haptic material, PMMA in particular being used as haptic material. The haptic material has a first modulus of elasticity E H  and the optic material a second modulus of elasticity E O , the ratio of the modules of elasticity E H /E O  preferably being greater than 1.5, particularly greater than 2, and in particular greater than 3. The haptic material also has a first refractive index B H  and the optic material has a second refractive index B O , the difference between the refractive indices B H -B O  amounting to at least 0.03, particularly 0.06 and in particular 0.09.  
      The intraocular lens  1  is implanted in the anterior chamber of an eye. It is used either as a replacement for the natural lens which was removed, for example due to a cataract, or is used in addition to the natural lens in order to correct defective vision. The intraocular lens I is inserted into the anterior chamber of the eye through an incision in the cornea and is attached to the iris by the haptic arms  12 . For this purpose, the iris is clamped between the haptic arms  12  in the nipping gap  11  in the haptics  3 . The width of the nipping gap  11  and the average surface roughness of the end faces  21  are in such a way that the intraocular lens  1  is reliably attached to the iris by the haptics  3 . The haptic arms  12  rest on the iris with their posterior lateral surfaces facing the iris so that the optic  2  is raised from the iris due to the haptic straps  13  extending obliquely to the lens plane  5 , and is exposed. Since only the haptic arms  12  are in contact with the iris, the intraocular lens  1  has a good compatibility. The sharp-edged configuration of the optic edges  9 ,  10  and the peripheral surface  8  extending parallel to the optical axis  4  reduce imaging defects, so that the intraocular lens  1  has very good imaging characteristics. When forces are exerted on the haptics  3 , the geometry of the haptics  3  and their attachment to the optic  2  allow a uniform introduction of such force into the optic  2 , thereby reducing imaging defects due to a deformation of the optic  2 . In addition, the coating  20  between the haptic material and the optic material reduces imaging defects caused by disturbing light effects, by virtue of the haptic straps  13  extending in the optic material.