lamellar keratoplasty A new surgical technique for deep stromal, anterior

Aims—To describe a new surgical technique for deep stromal anterior lamellar keratoplasty. Methods—In eye bank eyes and sighted human eyes, aqueous was exchanged by air, to visualise the posterior corneal surface−that is, the “air to endothelium” interface. Through a 5.0 mm scleral incision, a deep stromal pocket was created across the cornea, using the air to endothelium interface as a reference plane for dissection depth. The pocket was filled with viscoelastic, and an anterior corneal lamella was excised. A full thickness donor button was sutured into the recipient bed after stripping its Descemet’s membrane. Results—In 25 consecutive human eye bank eyes, a 12% microperforation rate was found. Corneal dissection depth averaged 95.4% (SD 2.7%). Six patient eyes had uneventful surgeries; in a seventh eye, perforation of the lamellar bed occurred. All transplants cleared. Central pachymetry ranged from 0.62 to 0.73 mm. Conclusion—With this technique a deep stromal anterior lamellar keratoplasty can be performed with the donor to recipient interface just anterior to the posterior corneal surface. The technique has the advantage that the dissection can be completed in the event of inadvertent microperforation, or that the procedure can be aborted to perform a planned penetrating keratoplasty. (Br J Ophthalmol 1999;83:327–333) Anterior lamellar keratoplasty is a surgical procedure in which the anterior layers of the cornea (epithelium, its basement membrane, Bowman’s layer, and stroma) to a variable depth, are replaced by donor tissue. Commonly, the anterior stroma is incised with a trephine that can be set to a depth not exceeding the corneal thickness. From the bottom of the incision, several corneal layers may be dissected until the desired depth of the recipient stromal bed is obtained. Compared with a penetrating keratoplasty, a lamellar procedure has the advantage of avoiding most complications associated with “open sky” surgery, easier postoperative management, and less risk of allograft rejection and other long term complications. Despite these benefits, surgeons commonly perform a penetrating keratoplasty for anterior corneal disorders because the latter technique is easier to perform, and lamellar transplants often show decreased best corrected visual acuity owing to irregular astigmatism and/or scarring at the donor to recipient interface. 12 Less scarring may occur with deeper—that is, smoother keratectomies, and techniques such as air injection in, and hydrodelamination or photoablation of the posterior stroma have been advocated to obtain a deep recipient stromal bed. 13–18 With all these techniques the stromal dissection depth relative to the corneal thickness cannot be optically visualised. The posterior corneal surface is invisible through an operating microscope, owing to the small diVerence in the refractive index between corneal tissue and aqueous. Lamellar dissection techniques therefore bear the risk of inadvertent perforation when deeper dissections are intended. If perforation occurs completion of the stromal dissection can be diYcult, so that the donor button may have to be sutured into an imperfectly prepared recipient bed. When conversion of the procedure into a penetrating keratoplasty is required, donor tissue with good quality endothelium may not be available. The purpose of our study was to design a lamellar keratoplasty surgical technique in which a stromal dissection can be made to a visually controlled depth during surgery, and which allows for completion of the dissection in the event of a microperforation, or abortion of the entire procedure until a planned penetrating keratoplasty can be performed. Materials and methods HUMAN EYE BANK EYE MODEL Sixty two human eye bank eyes were obtained through Bio Implant Services, Leiden, and the Cornea Bank of the Netherlands Ophthalmic Research Institute, Amsterdam. Thirty eyes Table 1 Experimental and clinical corneas evaluated