This invention relates to correction of injured or defective eyes, and more particularly to a synthetic corneal implant in the nature of a biological window which can be permanently substituted for the damaged area in corneal tissue. By virtue of its clarity and biological compatibility, the material of this invention can also serve as a permanently implantable lens.
Occassionally the corneal tissue which overlies the fore part of the human eyeball becomes injured or a growth forms therein which will create opaque areas in the cornea. If such opaque or lumpy areas occur over the pupil, then the person thus afflicted will be blind or at least have his vision partially obscured.
Presently, when a cornea has become diseased to a point where replacement is warranted, the only truly effective method for such replacement is to perform a cornea transplant. Of course, the performance of a cornea transplant requires that a cornea be available and that the recipient be able to immunologically tolerate the transplant.
While the technique of making corneal transplants from eyes stored in so-called "eye banks" is highly developed, the percentage of successful operations is decidedly in the minority. Such operations are less than thirty (30) percent successful and the most reliable figures available indicate that in only sixteen (16) percent of the cases was there any improvement in visual acuity.
Present day practice in repairing damaged corneas involves replacing a carefully cut-out circular or square portion of the cornea with that of a donor which has been cut exactly to the same dimensions and configuration. The newly grafted cornea is then permitted to heal and form a transparent window through which the patient can see clearly. The operation is extremely critical and a high percentage of failures occurs because the corneal implant does not properly graft or will deteriorate, again becoming opaque. The major reasons for failure are clouding of the graft and ingrowth of blood vessels and these failures have suggested the desirability of an artificial graft into which the blood vessels could not grow, and around which granulation tissue would not cloud the normal field of vision. Such clouding conditions greatly decrease the number of cornea transplants that can be performed.
Various attempts have been made to provide such grafts in the form of synthetic windows. In these windows, various transparent materials have been used but even when these were sufficiently inert to be tolerated, the grafts, although sutured in place, soon extruded. It is, of course, highly desirable to have a synthetic material that can be used as an artificial cornea for a cornea transplant.
In order for a synthetic material to be successful for use in Keratoprosthesis, the material must meet a number of criteria. For example, the material must be compatible with the tissue in the human eye. The material must be optically clear. It must also be tough and easy to fabricate. Up to the present time, such a material which meets all of the foregoing criteria has not been found.