RESUMEN
AIM: To investigate the safety and efficacy of undersurface ablation of the flap ( UAF ) for laser in situ keratomileusis ( LASIK ) retreatment in eyes with regression. METHODS: Twelve patients ( 22 eyes ) with regression after LASIK were performed undersurface ablation of the flap. The mean of preoperative refractive error was -2. 27±0-88D, the astigmatism was -0. 44±0. 30D, the central corneal thickness was 424. 9±8. 2μm. The follow-up time was 1a, including visual acuity, refractive error, the elevation of posterior cornea, WavScan. The data was analyzed with Student's t test andχ2test. RESULTS:During the operation, the measured stromal thickness was 275. 4±9. 3μm, the flap thickness 144. 7±7-5μm, the depth of ablation 28. 1±9. 3μm. The mean postoperative uncorrected visual acuity (UCVA) was 4. 99±0. 04, best corrected visual acuity ( BCVA) 5. 03±0. 04, at 1a follow up. There was no patient with postoperative BCVA decreasing, compared to preoperation. Mean spherical refraction decreased to-0. 22±0. 19 D at 1a follow up (t=10. 232, P CONCLUSION:UAF, as one of a choice, is an effective and safe procedure for the treatment of regression after LASIK, based on the reasonable surgery design.
RESUMEN
PURPOSE: To develop a newly modified technique, which is simultaneous laser in situ keratomileusis on both corneal flap undersurface (LASIK-Flap) and the corneal stromal surface, in eyes with insufficient corneal bed of high myopia and thin cornea. METHODS: We performed simultaneous laser in situ keratomileusis on both corneal flap undersurface (LASIK-Flap) and the corneal stromal surface in 38 eyes of 22 patients with high myopia (ranged from SE -4.00D to -14.25D)and corneal thickness (ranged from 435 to 570 micro meter) . In these eyes, all procedures of 130 ~ 160 micro meter thickness of the flap preparation with hinge were successfully made with a use of the Moria M2 microkeratome. The ablation on both the corneal surface and the flap undersurface using VISX star S4 with active track was performed with a plan of postoperative residual corneal stromal bed >250micro meter. We evaluated the changes of visual acuity, refractive error, pachymetry, corneal topography and mesotest for at least 6 months after surgery. Preservation of normal wet state on the flap in very important in procedures. RESULTS: Mean SE was -9.32 +/- 2.75D and mean corneal thickness was 513.37 +/- 36.96 micro meter ranged from 435 micro meter to 570 micro meter before LASIK. Ablation depth of flap undersurface was 48.87 +/- 26.67 micro meter ranged from 6 micro meter to 100 micro meter, and post LASIK spherical equivalent was +0.02 +/- 0.62D (ranged +2.50 ~ -1.50D). No vision concerned complication was found. Follow-up was ranged from 1week to 6 months. CONCLUSIONS: LASIK-flap procedure has an advantage in eyes with insufficient corneal thickness in high myopia.