A laboratory model for microkeratome-assisted posterior lamellar keratoplasty utilizing a running graft suture and a sutureless hinged flap

Purpose. To evaluate changes in anterior corneal curvature and graft stability with different sized donor buttons in a laboratory model of posterior lamellar keratoplasty. Methods. Thirty-six human eye bank corneas (18 donors and 18 recipients) were mounted on an artificial anterior chamber. A manual microkeratome was used to create a hinged anterior lamellar keratectomy. A 7.0-mm diameter posterior lamellar disk (posterior stroma. Descemet's membrane. and endothelium) was then trephinated from the recipient cornea. Three different sizes (7.0, 7.25. and 7.5 mm) of donor buttons were compared. They were sutured into the recipient bed with a running 10-0 nylon suture and covered by the host corneal flap. The nap was replaced without sutures. The resulting endokeratoplasty was analyzed by computerized videokeratography and tonometry. Results. Regular postoperative astigmatism was present in all cases. There was an average increase in astigmatism of 1.47 +/- 1.49 diopters (D) postoperatively. The mean change in the average keratometry readings was -5.12 +/- 6.12 D. The grafts and nap,, maintained watertight seals with average leak pressures of 06.9 +/- 46.4 mm Hg. Although donor buttons oversized by 0.5 mm had the least change in average keratometry reading, those oversized by 0.25 mm had the best stability at high pressure. All groups had little change in astigmatism. Conclusion. The optimal sized button of those tested should be either oversized by 0.25 or 0.5 mm. This new surgical technique may result in lower risk of high and irregular astigmatism in the management of corneal endothelial disorders.