Abstract:
A lens delivery system having a plunger rod with a sliding block reinforcing member. The sliding block rides on and along with the plunger rod and helps to reinforce the plunger rod against bending or buckling during use.

Description:
This invention relates to intraocular lenses (IOLs) and more particularly to devices used to inject IOLs into an eye. 
     BACKGROUND OF THE INVENTION 
     The human eye in its simplest terms functions to provide vision by transmitting and refracting light through a clear outer portion called the cornea, and further focusing the image by way of the lens onto the retina at the back of the eye. The quality of the focused image depends on many factors including the size, shape and length of the eye, and the shape and transparency of the cornea and lens. 
     When trauma, age or disease cause the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. The treatment for this condition is surgical removal of the lens and implantation of an artificial lens or IOL. 
     While early IOLs were made from hard plastic, such as polymethylmethacrylate (PMMA), soft, foldable IOLs made from silicone, soft acrylics and hydrogels have become increasingly popular because of the ability to fold or roll these soft lenses and insert them through a smaller incision. Several methods of rolling or folding the lenses are used. One popular method is an injector cartridge that folds the lenses and provides a relatively small diameter lumen through which the lens may be pushed into the eye, usually by a soft tip plunger. One of the most commonly used injector cartridge design is illustrated in U.S. Pat. No. 4,681,102 (Bartell), and includes a split, longitudinally hinged cartridge. Another recently introduced disposable lens delivery system is disclosed in U.S. Pat. No. 7,156,854 B2 (Brown, et al.). Other cartridge designs are illustrated in U.S. Pat. Nos. 5,494,484 and 5,499,987 (Feingold) and U.S. Pat. Nos. 5,616,148 and 5,620,450 (Eagles, et al.). In an attempt to avoid the claims of U.S. Pat. No. 4,681,102, several solid cartridges have been investigated, see for example U.S. Pat. No. 5,275,604 (Rheinish, et al.) and U.S. Pat. No. 5,653,715 (Reich, et al.). 
     The ability to express a lens out of a cartridge without damage is dependent on lens design and material. Silicone lenses, being made from a relatively rugged and durable material, can be compressed more aggressively. High water content hydrogel material, being more fragile, must be folded more gently. Soft acrylics, being viscoelastic in nature, are highly sensitive to temperature, and can be brittle if too cold, and can be unworkable if too warm. Soft acrylics, when compressed at an appropriate temperature, can be described as “flowing” rather than folding. For this reason, soft acrylics are best compressed slowly and in a very controlled manner. 
     Prior art lens delivery handpiece suitable for use with soft acrylic IOLs generally have plungers with very long plunger rods. The long stroke on these handpieces causes the lens to be folded more slowly as the lens is pushed down the relatively long length of the folding cartridge. As preferred incision sizes have gotten smaller, the diameter of the cartridge nozzle has also gotten smaller, forcing the lens to be compressed much more tightly than in the past. The force require to push the lens down the cartridge nozzle has increased correspondingly. This increase force on the plunger rod can cause the plunger rod to buckle or bend. 
     Accordingly, a need continues to exist for a device to help prevent bending or buckling of a lens delivery handpiece plunge rod during use. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention improves upon prior art by providing a lens delivery system having a plunger rod with a sliding block reinforcing member. The sliding block rides on and along with the plunger rod and helps to reinforce the plunger rod against bending or buckling during use. 
     It is accordingly an objective of the present invention to provide a lens delivery system that is suitable for folding lenses made from a soft acrylic material. 
     It is a further objective of the present invention to provide a lens delivery system having a sliding block. 
     It is a further objective of the present invention to provide a lens delivery system having a device for helping to resist bending and buckling of the plunger rod. 
     Other objectives, features and advantages of the present invention will become apparent with reference to the drawings, and the following description of the drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an enlarged partial perspective view of the distal end of the lens delivery handpiece or system of the present invention. 
         FIG. 2  is an enlarged partial perspective view of the sliding block installed on lens delivery handpiece or system of the present invention. 
         FIG. 3  is an enlarged partial perspective view of the sliding block of the present invention. 
         FIG. 4  is an enlarged side elevational view of the sliding block of the present invention installed on a plunger rod. 
         FIG. 5  is an enlarged top plan view of the sliding block of the present invention installed on a plunger rod. 
         FIG. 6  is a top plane view of the lens delivery system of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As best seen in  FIGS. 1 and 6 , lens delivery system  10  of the present invention generally includes cartridge  12  and handpiece  14 . As best seen in  FIG. 1  cartridge  12  generally has tubular body  16  and injection nozzle  18 . Cartridge  12  is molded as a single piece from any suitable thermoplastic, such as polypropylene, and the thermoplastic may contain a lubricity enhancing agent such as those disclosed in U.S. Pat. No. 5,716,364, the entire contents of which are incorporated herein by reference. Alternatively, cartridge  12  may be integrally formed with handpiece  14 . Nozzle  18  preferably is round, oval or elliptical in cross-section and has a cross-sectional area of between around 1.0 mm 2  to around 2.6 mm 2 . Cartridge  12  contains chamber  20  for receiving lens  22  to be folded. Lens  22  is pushed out of chamber  20  and down nozzle  18  by plunger rod  24  in a manner well-known in the art. 
     As best seen in  FIGS. 3, 4 and 5 , sliding block  26  that may be used with the lens delivery system of the present invention generally consists of elongated body  28  having channel or groove  30  and actuation button  32 . Groove  30  is sized and shaped to fit over and slide upon plunger rod  24 . Plunger rod  24  is attached to, and extends distally from, plunger  25  and contains detents  34  that engage pins  36  contained within groove  30  so that movement of sliding block  26  within slot  27  of cartridge  12  also causes movement of plunger rod  24  and plunger  25 , as will be described below. 
     In use, plunger  25  is pulled proximally (away from nozzle  18 ) so that plunger rod  24  and sliding block  26  are retracted within handpiece  14  exposing chamber  20  allowing lens  22  to be placed in chamber  20  as seen in  FIGS. 1, 2 and 6 . Sliding block  26  is advanced forward by pushing actuation button  32  distally to one of multiple, pre-measured desirable distances (graduation marks  1 ,  2  and  3  in  FIG. 2 ). Movement of sliding block  26  also causes movement of plunger rod  24  because of the interlocking arrangement of detents  34  and pins  36 . As sliding block  26  is pushed distally, a series of staging detent stops  35  may be provided so as to indicate to the user a particular stage of the lens delivery process. Sliding block  26  may in continued to be pushed distally until button  32  reaches distal end  37  of slot  27 , thereby preventing any further movement of sliding block  26 , as indicated in  FIG. 1 . Further movement of plunger rod  24  is accomplished by pressing on end cap  39  of plunger  25 , which causes plunger rod  24  to overcome the holding force of detents  34  and pins  36  to push lens  22  distally out of chamber  20 , through cartridge  12  and out nozzle  18 . During this further movement of plunger rod  24 , body  28  of sliding block  26  acts as a stiffener, helping to reduce bending and buckling of plunger rod  24 . 
     While certain embodiments of the present invention have been described above, these descriptions are given for purposes of illustration and explanation. Variations, changes, modifications and departures from the systems and methods disclosed above may be adopted without departure from the scope or spirit of the present invention.