التقنيات الحديثة في ترقيع القرنية

                "Recent Advancesin Corneal Grafting

                Penetrating keratoplasty is a full thickness, relatively easy surgical procedure to perform and with improvements both in surgical technique, material and donor storage, the outcome is generally good.

                There have been many advances in penetrating keratoplasty, not so much in the technique, but in the suture materials used, and types of different suturing techniques.

                Penetrating keratoplasty, it must be remembered, is also an intraocular procedure, with all its inherent operative risks including damage to the iris, chamber angle, and lens. Endophthalmitis, although rare, is a devastating but possible complication. The main drawback of penetrating keratoplasty is the postoperative loss of grafts as a result of endothelial rejection. Graft rejection, despite the advances in its management, remains the major cause of corneal graft failure.

        Advances in corneal storage media, and facilities has lengthened the storage time and decreased the incidence of infections. In addition, introduction of tissue typing in terms of donor-recipient corneas has decreased the incidence of graft rejection.

                Lamellar keratoplasty was introduced as a logical step in the surgical treatment of corneal opacification where the endothelium remains functional. Unlike in penetrating keratoplasty, where endothelial cell viability is critical to graft success, in lamellar keratoplasty donor endothelium is not a consideration. By preserving the recipient's own healthy endothelium the risk of endothelial rejection is virtually eliminated.

        Lamellar keratoplasty seems to be nearly replacing penetrating keratoplasty due to various modalities in graft depth control and easier harvesting of various layers of a donor cornea.

                Other obvious attractions of lamellar keratoplasty include the fact that it remains an extraocular procedure and thus avoids possible intraocular damage. It also limits postoperative astigmatism and rehabilitation time.

                Davis, in 1910 reported the use of fetal membranes as a skin substitute. AMT became important because of its ability to diminish the occurrence of adhesions and scarring, its ability to enhance wound healing and epithelialisation, and its antimicrobial potential. In particular, the amniotic membrane expresses incomplete HLA-A, B, C, and DR antigens, which may account for the fact that immunological rejection after transplantation has not been observed.  

                Trends in keratoplasty have been changing over the past decade. Ocular surface reconstruction, consisting of limbal transplantation combined with amniotic membrane transplantation,has enabled us to improve the management of cicatrising diseases.

                Amniotic membrane has been successfully used in a number of procedures for restoration of the ocular surface. As its mechanism of action becomes more fully understood, its application will become more refined, with more appropriate usage of this valuable technique. The full potential of this technique is not known, thus randomised prospective studies are needed."