Purpose: Femtosecond lasers have revived the possibility of stromal keratophakia or tissue additive keratoplasty, a technique originally introduced by Prof. Jose Ignacio Barraquer in the 1960s. The surgical technique offers a unique solution to treat keratoconus. In the current study, we reviewed and performed a meta-analysis of the clinical outcomes of the femtosecond laser-assisted stromal keratophakia in the treatment of keratoconus.
Methods: This is a systematic review and meta-analysis of the estimated outcome difference between pre- and post-lenticule implantations.
Results: A total of related 10 studies were found in the literature. No studies reported adverse events, such as persistent haze or graft rejection, at last patients' visits. We further narrowed down the article selection in accordance to our inclusion criteria to report the composite outcomes (9 studies) and meta-analysis (4 studies). In the composite analysis, we demonstrated that lenticule implantation in keratoconus and post-LASIK ectasia patients appeared to expand the stromal volume of the thin corneas, flattened the cones, and significantly improved uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and spherical equivalent (SE). The meta-analysis showed that the random estimated UCVA, BCVA, SE and mean keratometry (Km) differences following the lenticule implantation was -0.214 (95% CI: -0.367 to 0.060; p = 0.006), -0.169 (-0.246 to 0.091; p < 0.001), -2.294 D (-3.750 to -0.839 D; p = 0.002), and 2.909 D (0.805 to 5.012 D; p = 0.007), respectively.
Conclusions: Femtosecond laser-assisted stromal keratophakia is a feasible technique to correct the refractive aberrations, expand corneal volume and regularize corneal curvature in patients with keratoconus. However, there is a need to standardize the technique (e.g., whether to crosslink or not or to use convex or concave lenticules) and to formulate a mathematical model that accounts for the long-term epithelial thickness changes and stromal remodeling to determine the shape or profile of the lenticules, in order to improve the efficacy of the keratophakia further.
Keywords: Femtosecond laser; Keratoconus; Keratophakia; Refractive lenticule; SMILE; Visual acuity.