Factors that lead to early postoperative suture loosening after optical lamellar keratoplasty for keratoconus

Abstract

Objective To investigate the factors that lead to early postoperative suture loosening after optical lamellar keratoplasty (LKP) for keratoconus. Methods Retrospective case series study. Keratoconous patients who received LKP in Shandong Eye Hospital between January 2006 and May 2010 were reviewed. The case histories of 52 patients (56 eyes) who underwent surgery before November 2009 were reviewed retrospectively. Patients were divided into two groups: a suture-loosening group (37 eyes) and a non-suture-loosening group (19 eyes). Corneal topography, pachymetry, keratometry, axial length, corneal diameter and corneal preservative methods used were analyzed. Nine patients who underwent surgery during November 2009 to May 2010 were examined by slit lamp, anterior segment optical coherence tomography, and laser confocal microscopy, with the purpose of studying the local features of early postoperative sutures. Results Of the 56 eyes reviewed retrospectively, early postoperative suture loosening occurred in 37 eyes (66%), with graft fissure occurring in 27 of those eyes (73%), and 96% of these fissures occurred in the first three months after surgery. Suture loosening mainly occurred in the inferior cornea (62%), 47% of the graft fissures occurred in the same quadrant as the apex and the thinnest point of the lesion. When the suture-loosening group and the non-suture-loosening group were compared, there were no significant differences in the distribution in the apex (x2=1.62, P＞0.05) and the thinnest point (x2=3.49, P＞0.05), or corneal thickness in the central (u=0.11, P＞0.05) and thinnest points (u=0.21, P＞0.05).And there were no significant differences in maximum curvature (u=0.66, P＞0.05), axial length (u=1.06, P＞0.05), corneal diameter (u=1.68, P＞0.05), or corneal preservative methods used (x2=3.06,P＞0.05). Anterior segment optical coherence tomography showed that the ratio of the suture spanning depth in the corneal tissue and the thickness of the cornea was significantly different between the two groups (0.4258±0.0420 versus 0.4869±0.0609, u=2.32, P＜0.05). Slit lamp and confocal microscopy showed that many of the eyes in the suture-loosening group suffered from new vessel formation and the sutures were primarily loosening on the limbus side of the cornea. Necrotic tissue, cicatricle and inflammatory cells were also found in the suture-loosening area. Conclusion Suture loosening and graft fissures often occur during the early period after LKP for keratoconus, and the loosening tends to be located in the inferior cornea. Insufficient spanning depth of the suture in corneal tissue,inflammatory reaction, new vessel formation, and keratopathy may be causes of suture loosening. Key words: Keratoplasty,lamellar; Keratoconus; Suture loosening