Early Changes Among FLEx, LASIK and FS-LASIK
Condition: Myopia; Astigmatism
MeSH terms: Astigmatism
Study type: Interventional

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

Detailed description: 
      Laser in situ keratomileusis (LASIK) with a microkeratome has been accepted wildly in the
      past 20 years. Gradually, 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 analyze the short-term changes in ocular surface
      measures and tear inflammatory mediators after FLEx, LASIK and FS-LASIK procedures.
    

Intervention name(s): lenticule extraction; laser in situ keratomileusis; FS assisted laser in situ keratomileusis
Intervention type(s): Procedure; Procedure; Procedure
Intervention description(s): Four femtosecond incisions will be 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 is released, the flap will be opened using a thin, blunt spatula and the free refractive lenticule will be subsequently grasped with a forceps and extracted, after which the flap will be repositioned carefully.; During LASIK surgery, the eye will be gently proptosed and a hinged corneal flap will be cut using a microkeratome. The flap will be lifted and the stromal bed will receive a 6 mm diameter and stroma ablation. Finally reposition the flap carefully.; Track distance and spot distance will be 3.0 μm during flap creation and 1.5 μm during flap side-cutting. The flap diameter will be 8.0 mm, and flap thickness will be set to 105 μm. Side-cut angle and hinge angle will be 90°and 50° respectively. The flaps will be created by laser scanning in spirals from the periphery to the center of the pupil. An excimer laser system will be used in the subsequent ablation of thstromal bed with a 6.0 mm optical zone. Once the excimer. ablation is completed, the flap will be repositioned in a similar fashion as in routine LASIK.
Other intervention name(s): 0.3% tobramycin/dexamethasone (TobraDex, Alcon); 0.5% levofloxacin (Cravit, Santen); sodium hyaluronate (HYCOSAN,URSAPHARM Arzneimittel GmbH); 0.3% tobramycin/dexamethasone (TobraDex, Alcon); 0.5% levofloxacin (Cravit, Santen); sodium hyaluronate (HYCOSAN,URSAPHARM Arzneimittel GmbH); 0.3% tobramycin/dexamethasone (TobraDex, Alcon); 0.5% levofloxacin (Cravit, Santen); sodium hyaluronate (HYCOSAN,URSAPHARM Arzneimittel GmbH)
Intervention MeSH terms: Levofloxacin; Ofloxacin; Tobramycin; Tobramycin, Dexamethasone Drug Combination; Dexamethasone; Dexamethasone acetate; BB 1101; Hyaluronic Acid; Dipivefrin
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: lenticule extraction; laser in situ keratomileusis; femtosecond laser-assisted laser in situ keratomileusis; tear; inflammatory mediators