Early Changes Between Lenticule Extraction and Small-Incision Lenticule Extraction
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 small-incision lenticule
      extraction (SMILE) procedures.
    

Detailed description: 
      The use of femtosecond (FS) laser has become one of the most significant technological
      advancements in refractive surgery. A breakthrough FS laser-assisted myopic and myopic
      astigmatic correction procedure can now be performed using a prototype femtosecond system.
      This first all-in-one FS-laser system was designed to perform the refractive lenticule
      extraction (ReLEx) procedures, femtosecond lenticule extraction (FLEx) and small-incision
      lenticule extraction (SMILE). In FLEx, a corneal flap is created by the FS laser (similar to
      LASIK) and lifted, allowing lenticule removal. For SMILE, a truly without flap procedure,
      only a small-2-4mm- incision is made, through which the lenticule is removed.

      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.

      For both FLEx and SMILE, stromal ablation has been replaced by refractive lenticule removal.
      In terms of corneal flap formation, FLEx still requires an epithelial-stromal flap, while
      SMILE employs only a small incision to extract the lenticule. Hence, the investigators
      hypothesize that SMILE will have less effect on patients' ocular surface markers and
      inflammatory mediators, compared to FLEx. In support of this hypothesis, previous studies
      have reported that more damage to the sub-basal nerve plexus of the cornea and more changes
      in ocular surface evaluations were found after FLEx than after SMILE. In this study, the
      investigators have focused on postoperative changes to tear inflammatory mediators and the
      relationship of FLEx and SMILE to dry eye.
    

Intervention name(s): lenticule extraction; small-incision lenticule extraction
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; 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), make a small incision
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)
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: Refractive Surgical Procedures; small-incision lenticule extraction; lenticule extraction; inflammatory mediators