As shown in FIG. 1 (the drawing showing the various parts of the eye), the lens 11 is perhaps the most critical element within the eye in providing vision for the human or animal. It is suspended behind the cornea 12, the anterior chamber 13 and the iris 14 by the zonular fibers which connect it with the ciliary body of muscles 15 around its periphery.
The lens is composed of a central region, the nucleus 16, surrounded by a softer outer region, the cortex 17. It is encapsulated in the lens capsule 18o which is a thin transparent membrane. The front part of the membrane is called the anterior capsule 20, and the rear part, the posterior capsule 21.
The function of the lens is to focus light rays upon the sensitive retina 19. To focus light from a distant object, the ciliary muscles 15 relax, thus tightening the zonular fibers and reducing the thickness of the lens to its minimal dimension. To focus light from a near object, the ciliary muscles 15 release the tension on the zonular fibers to increase the thickness of the lens, the lens assuming a near spherical shape. This change increases the lens refractive power to again obtain focusing of the light rays on the retina 19.
The lens consists of about 35% protein and 65% water. When the proteinaceous material hardens or becomes suffused with minerals, the lens becomes cloudy or opaque. A cloudy lens or an opaque, non-functional lens is a cataract. Most cataracts are not visible to the casual observer until they become dense enough to cause blindness.
Cataract surgery involves the removal of the "diseased" lens from the eye. Two principal procedures for lens extractions are practiced currently. Intracapsular surgery involves removal of the lens together with its surrounding capsule. Where the posterior capsule may be attached slightly to the vitreous membrane, extracapsular extraction of the lens is much preferred. Rupturing the vitreous membrane, a definite hazard in intracapsular surgery, has serious consequences, including vitreous loss, vitreous hemorrhage, retina detachment etc.
This invention relates to extracapsular extraction, the procedure considered the safest. However, even in extracapsular surgery where a probe or similar instrument is used to remove the lens, either as a complete lens or by first dissolving the cortex and then shattering or breaking down the nucleus into smaller bits or pieces and extracting the bits, the danger of the surgical instrument penetrating through the posterior capsule exists, even with the most careful surgeon. Vitreous loss or hemorrhage, retina detachment, etc. may result.
One of the currently used procedures for extracapsular extraction of cataracts is disclosed in U.S. Pat. No. 3,996,935. For this procedure, the anterior capsule is first ruptured and removed, followed by removal of the cortex and nucleus of the lens, leaving the posterior capsule intact.
The primary object of the present invention is to reduce the chances to substantially zero of penetrating the posterior capsule in performing cataract surgery while retaining the anterior capsule substantially intact.
A further object is to provide an instrument or device for achieving a successful procedure for removing unwanted objects from within the body without injuring neighboring body tissue.
A still further object is to provide a device that will not only almost insure success in cataract surgery, but provide an option to the surgeon for simplifying the procedure, using a smaller incision to retain the anterior capsule substantially intact and to use less complicated secondary instrumentation than had previously been necessary.