Femtosecond lenticule extraction (FLEx): clinical results, interface evaluation, and intraocular pressure variation.

PURPOSE To characterize the clinical profile of femtosecond lenticule extraction (FLEx) correlated with ultrastructural analysis of the corneal interface and in vivo real-time intraocular pressure (IOP). METHODS Prospective clinical case series with experimental studies; consecutive patients underwent FLEx at a single tertiary center over 10 months with postsurgical follow-up of 3 months. The patients were divided into three groups according to spherical equivalence (SE) (A, < -5.0 diopters [D]; B, ≥ -5.00 D and < -9.00 D; and C, ≥ -9.0 D). Twelve human cadaveric eyes analyzed using scanning electron microscopy after receiving FLEx; 40 rabbit eyes received FLEx with in vivo IOP measurements. The main outcome measures were refractive outcomes from study subjects; with corneal interface and IOP in experimental studies. RESULTS Thirty-three subjects (22 females, 66.7%) underwent FLEx in both eyes (66 eyes). Mean age was 32 years (range, 21 to 46 years). Preoperative mean SE was -5.77 ± 2.04 D with astigmatism of -1.03 ± 0.72 D. There was a slight hyperopic shift (mean SE 0.14 ± 0.53 D); 94% achieved uncorrected visual acuity ≥20/25 3 months postoperatively. Refractive stability was achieved within 1 month (P < 0.001). Ultrastructurally, the smoothness of the corneal interface was independent of ablation depth (mean irregularity scores A, B, C: 8.8 ± 0.6, 10.3 ± 0.4, 8.7 ± 0.6, respectively; P = 0.88). The increase in IOP during FLEx was similar to that in femtosecond (FS)-LASIK, albeit a twofold duration of raised IOP in FLEx (P < 0.001). CONCLUSIONS These results suggest that FLEx is predictable and effective in treating myopia and myopic astigmatism. Experimental studies support the early clinical results and safety of this procedure.