Changes Between Lenticule Extraction and Femtosecond Laser-assisted Laser in Situ Keratomileusis
Condition: Myopia; Astigmatism
MeSH terms: Astigmatism
Study type: Interventional

Summary: 
      The aim is to evaluate the short-term changes in ocular surface measures and tear
      inflammatory mediators after lenticule extraction (FLEx) and femtosecond laser-assisted laser
      in situ keratomileusis (FS-LASIK) procedures.
    

Detailed description: 
      Over the past few years, laser in situ keratomileusis with a femtosecond laser-created flap
      (FS-LASIK)has been a popular ophthalmic procedure for the correction of refractive error.
      This first all-in-one FS-laser system was designed to perform the refractive lenticule
      extraction (ReLEx) procedures, femtosecond lenticule extraction (FLEx).They have the same
      feature: corneal flap.

      Ocular surface disruption during corneal refractive surgery is commonly considered to be
      closely related to the development of dry eye. Multiple etiologies contribute to this ocular
      surface disruption, including the flap creation and stromal ablation involved in previous
      refractive surgery techniques. Corneal nerve damage has been considered the main cause of dry
      eye, due to disrupted afferent sensory nerves, reduced blink reflex, and increased tear
      evaporation leading to tear film instability. In addition, postoperative inflammatory
      mediator fluctuations are also a key factor related to ocular surface damage. Extensive
      research has described the effects of cytokines, chemokines and growth factors in modulating
      corneal wound healing, cell migration, and apoptosis on the ocular surface after refractive
      surgery.

      This prospective clinical study is going to assess the short-term changes in ocular surface
      measures and tear inflammatory mediators after lenticule extraction (FLEx) and femtosecond
      laser-assisted laser in situ keratomileusis (FS-LASIK) procedures.
    

Intervention name(s): lenticule extraction; femtosecond laser-assisted laser in situ keratomileusis
Intervention type(s): Procedure; Procedure
Intervention description(s): Four femtosecond incisions were created in succession: the posterior surface of the refractive lenticule (spiral in), the lenticule border, the anterior surface of the refractive lenticule (spiral out), and the corneal flap in the superior region. After the suction was released, the flap was opened using a thin, blunt spatula and the free refractive lenticule was subsequently grasped with a forceps and extracted, after which the flap was repositioned carefully.; track distance and spot distance were 3.0 μm during flap creation and 1.5 μm during flap side-cutting. The flap diameter was 8.0 mm, and flap thickness was set to 105 μm. Side-cut angle and hinge angle were 90°and 50° respectively. The flaps were created by laser scanning in spirals from the periphery to the center of the pupil. An excimer laser system was used in the subsequent ablation of the stromal bed with a 6.0 mm optical zone. Once the excimer ablation was completed, the flap was repositioned in a similar fashion as in routine LASIK.
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: lenticule extraction; femtosecond laser-assisted laser in situ keratomileusis; tear; inflammatory mediators