Abstract
AIM: To investigate the response of the anterior and posterior corneal surface in femtosecond laser-assisted convex stromal lenticule addition keratoplasty (SLAK) combined with cross-linking (CXL) for treating keratoconus at the first 3mo of follow-up. METHODS: In this prospective observational study, 20 eyes of 20 keratoconus patients who underwent SLAK combined with CXL were included. The morphological indices in keratometry and elevation data were recorded from the Sirius at baseline and 1 and 3mo postoperatively. The mean values of maximum keratometry (K(max)), flat keratometry (K(1)), and steep keratometry (K(2)) at the central, 3-mm, 5-mm, and 7-mm areas were measured from the curvature map. The changes 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, K(1), and K(2) at 3-mm, 5-mm, and 7-mm of the anterior corneal surface increased significantly 1mo postoperatively (all P<0.05) and remained unchanged until 3mo (P>0.05). For the back corneal curvature, K(1) and K(2) along the 3-mm back meridian significantly decreased after month 1 (P=0.002, 0.077, respectively). Posterior K(2)-readings along the 5-mm and 7-mm did not change after surgery (P>0.05). Anterior BFS decreased 1mo (P<0.001) postoperatively but remained unchanged until 3mo after SLAK (P>0.05). There was no change 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 1mo postoperatively (all P<0.05) and remained stable until 3mo (P>0.05). CONCLUSION: The myopic SLAK combined with CXL is an economical alternative for stabilizing the corneal surface in severe keraoconus. "Pseudoprogression" occurs in the early phase postoperatively, but it is not an indicator of keratoconus progression.