Response of the corneal surface changes after stromal lenticule addition keratoplasty combined with cross-linking for keratoconus

Abstract

BACKGROUND Corneal crosslinking (CXL) is used to stabilize corneas with a central thickness greater than 400 µm. In patients with more advanced keratoconus, traditional corneal transplantation may be required. In this study, we described the response of the anterior and posterior corneal surface in femtosecond laser-assisted convex stromal lenticule addition keratoplasty (SLAK) combined with CXL for treating keratoconus.METHODS Twenty eyes of 20 keratoconus patients who underwent SLAK combined with CXL were included. The morphological indices in terms of keratometry and elevation data were recorded from the Sirius at baseline and at 1 and 3 months postoperatively. The mean values of maximum keratometry (Kmax), flat keratometry (K1), and steep keratometry (K2) at central, 3-mm, 5-mm, and 7-mm area was measured from the curvature map. The change in anterior and posterior corneal elevation under the best-fit sphere (BFS) radius at seven points horizontally of the center, 3-mm, 5-mm, and 7-mm area from the center at both Nasal(N) and Temporal(T) side were measured from elevation map.RESULTS For the front corneal curvature, Kmax, K1, and K2 at 3-mm, 5-mm, and 7-mm of the anterior corneal surface increased significantly 1 month postoperatively (all P < 0.05) and remained unchanged until 3 months(P > 0.05). For the back corneal curvature, K1 and K2 along the 3-mm back meridian significantly decreased after month 1 (P = 0.002, 0.077, respectively). Posterior K-readings along the 5-mm and 7-mm did not change after surgery(P > 0.05). Anterior BFS decreased 1 month(P < 0.001) postoperatively but remained unchanged until 3 months after SLAK(P > 0.05). No change was found in posterior BFS before and after the surgery(P > 0.05). Anterior elevation at N5, N3, central, and T5 points and posterior elevation at central and T7 points shifted backward 1 month postoperatively (all P < 0.05) and remained stable until 3 months(P < 0.05).CONCLUSIONS The myopic SLAK combined with CXL is an economical alternative for stabilizing the corneal surface in severe keratoconus. "Pseudoprogression" occurs in the early phase postoperatively, but it was not an indicator of keratoconus progression. Anterior and posterior elevation underwent slight backward displacement after the surgery.