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Evolution of visual acuity, flap thickness, and optical density after laser in situ keratomileusis performed with a femtosecond laser
摘要： To describe the postoperative evolution of visual acuity, flap morphology, and stromal optical density femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). The study comprised 44 consecutive eyes that had FS-LASIK performed with the WaveLight FS200 and the Allegretto excimer laser to correct myopia. Visual outcomes, flap thickness, and stromal optical density were assessed 1 day, 1 week, 1 month, and 3 months postoperatively. A statistically significant improvement in the mean uncorrected distance visual acuity at 1 day (0.94 ± 0.2) and 1 week (0.93 ± 0.2) to 1 month (1.04 ± 0.2) and 3 months (1.11 ± 0.1) postoperatively (P < .05). At 3 months postoperatively, the femtosecond laser had good outcomes in efficacy (0.98 ± 0.1), safety (0.98 ± 0.1), and predictability (100% of eyes were within ± 0.5 D of emmetropia). The femtosecond-created flaps were slightly thicker than intended, the mean SD intraflap was 7.1 μm, the range between the thickest and thinnest points in each flap was 25.4 μm, and the mean flap thickness homogeneity was 7.6 μm at 3 months postoperatively. A progressive decrease in the optical density of the flap stroma and the residual stromal bed was detected during follow-up. The femtosecond laser study appears to be a safe, effective, and predictable platform to obtain LASIK flaps. The flaps were planar and homogeneous but slightly thicker than intended. The optical density of the flap stroma was slightly higher at early follow-up and decreased over time.
关键词： visual acuity,femtosecond laser,LASIK,flap thickness,optical density
更新于2025-09-16 10:30:52
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Direct and Indirect Flap Measurements in Femtosecond Laser–Assisted In Situ Keratomileusis
摘要： To compare direct and indirect LASIK flap thickness measurements using ultrasound and Scheimpflug technology. Eighty-two eyes treated with laser-assisted in situ keratomileusis refractive surgery using a femtosecond laser (IntraLase FS150) were prospectively included in the study. Flap thickness was set to 115 mm. Corneal flap thickness was measured using the direct method—ie, ultrasound pachymetry immediately after flap construction in the presence of cavitation bubbles—and indirect methods, with subtraction of intraoperative post-lift corneal thickness measured using ultrasound pachymetry (intrastroma) from preoperative central corneal thickness using ultrasound (Indirect-US) or Scheimpflug thinnest pachymetry (Indirect-Scheimpflug). Mean flap thickness was overestimated using the indirect methods, Indirect-US and Indirect-Scheimpflug (122.6 6 24.5 mm and 128.1 6 26.1 mm, respectively; P , 0.0060 and P , 0.0001, respectively). There were no significant correlations between the direct and indirect methods. Indirect-Scheimpflug was significantly higher (P = 0.0122) than Indirect-US. The closest average flap thickness compared with the set parameter of 115 mm was that of the direct method (115.6 6 8.6 mm; 95% confidence interval: 21.3 to 2.5; P = 0.5163). The direct method provided the lowest SD of all groups (SD: 8.64). The direct method of flap thickness measurement was the most comparable to the set parameter compared with the indirect subtraction methods. Additional studies are needed to determine which method allows for the most accurate measurement of flap thickness.
关键词： flap thickness,femtosecond laser,laser in situ keratomileusis,Scheimpflug,ultrasound
更新于2025-09-12 10:27:22