Working...
ClinicalTrials.gov
ClinicalTrials.gov Menu

Comparison of Clinical Outcomes of Small-incision Lenticule Extraction (SMILE) Between Different Cap Thickness.

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Know the risks and potential benefits of clinical studies and talk to your health care provider before participating. Read our disclaimer for details.
ClinicalTrials.gov Identifier: NCT03584555
Recruitment Status : Recruiting
First Posted : July 12, 2018
Last Update Posted : July 12, 2018
Sponsor:
Information provided by (Responsible Party):
Yonsei University

Brief Summary:

In the past two decades, the femtosecond laser (FSL) technology has been introduced in the corneal refractive surgery filed, and brought a remarkable innovation. It can make tissue dissection through photodisruption and plasma cavitation. Initially, the FSL was used predominantly to make a corneal flap when performing laser in situ keratomileusis (LASIK), which is followed by stromal ablation using excimer laser. A new surgical technique called femtosecond lenticule extraction (FLEx) has been developed that uses only FSL to dissect two interfaces to create refractive lenticule and then remove it, which is very similar with LASIK. Small incision lenticule extraction (SMILE) which is the advanced form of all-in-one FSL refractive technique does not make a corneal flap rather make small incision where the separated refractive lenticule is removed through, and the upper part of the corneal tissue is called cap. Since the clinical outcomes of SMILE were firstly published in 2011, SMILE has been widely used for correction of myopia or myopic astigmatism worldwide. SMILE provides excellent visual outcomes and has advantages including a lesser decrease in corneal sensitivity and absence of flap related complications compared to LASIK.

Because corneal ectasia after refractive surgery is the one of most terrifying complication, corneal biomechanics has been drawn interests to many researchers and clinicians. Theoretically, SMILE may preserve corneal biomechanics better than LASIK, because the anterior stroma which is stiffer than the posterior stroma remains intact in SMILE. However, there are some controversies, because previous studies investigating corneal biomechanics have been reported inconsistent outcomes, although SMILE has been reported equal to or better than LASIK. Weakening of corneal biomechanics and iatrogenic corneal ectasia have also been reported after SMILE. In addition, because the tensile strength of cornea gradually decreases as it goes backwards, creating deeper refractive lenticule may result in stronger cornea by preserving more of anterior lamellae of the cornea. But on the contrary, leaving sufficient residual stromal bed has been known to be important in preventing iatrogenic corneal ectasia, hence creating thin cap may be effective and desirable. Although many researches have been investigated the difference in biomechanical response between SMILE and LASIK, there are few studies evaluating the dependence of cap thickness on postoperative biomechanical strength after SMILE. El-Massry et al. reported that the thicker cap thickness showed higher postoperative corneal hysteresis (CH) and corneal resistance factor (CRF) with Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Depew, NY) which may not be optimal for a clear description of the viscosity and elasticity of the cornea,3 ; however, other studies have been presented that there is no significant difference of corneal biomechanics with cap thickness. There is no comparative human study using Corvis ST (Oculus, Wetzlar, Germany) despite presence of the study using Corvis ST in rabbit eyes. Furthermore, no prospective study with large number of subjects has been performed to date.


Condition or disease Intervention/treatment Phase
Myopia Procedure: SMILE using 120μm cap thickness Procedure: SMILE using 140μm cap thickness Not Applicable

Layout table for study information
Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 200 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Intervention Model Description: Enrollment period : 24 months after IRB approval Methods: The subjects are randomly divided into two groups. One group underwent SMILE surgery using 120 μm cap thickness, and the other group underwent SMILE surgery using 140 μm cap thickness. Before surgery, all patients underwent a detailed ophthalmological examination that included evaluation of logarithm of the minimum angle of resolution (logMAR) uncorrected-distance visual acuity (UDVA) and CDVA, manifest refraction, slit-lamp examination (Haag-Streit, Köniz, Switzerland), keratometry, and Scheimpflug-based corneal topography (Pentacam HR, Oculus). Dynamic corneal response (DCR) parameters were examined using Corvis ST. Corneal wavefront aberrations were measured using Keratron Scout (Optikon 2000, Rome, Italy). All examinations were repeated at 1, 3, and 6 months after surgery.
Masking: None (Open Label)
Primary Purpose: Treatment
Official Title: Comparison of Clinical Outcomes of Small-incision Lenticule Extraction (SMILE) Between Different Cap Thickness.
Actual Study Start Date : March 18, 2017
Estimated Primary Completion Date : March 17, 2019
Estimated Study Completion Date : March 17, 2019

Resource links provided by the National Library of Medicine


Arm Intervention/treatment
Active Comparator: 120 μm group
The subjects underwent SMILE using 120 μm cap.
Procedure: SMILE using 120μm cap thickness
The surgery was performed with standardized techniques with triple centration technique using the 500-KHz VisuMax system (Carl Zeiss Meditec AG, Jena, Germany). The superior cap depth was set as 120 or 140 µm, and the length of the side cut was set to 2 mm. Once the anterior (upper) and posterior (lower) planes of the lenticule were defined, the anterior and posterior interfaces were dissected using a micropetala with a blunt circular tip and extracted with midforceps. The integrity of the lenticule was assessed subsequently.

Active Comparator: 140 μm group
The subjects underwent SMILE using 140 μm cap.
Procedure: SMILE using 140μm cap thickness
The surgery was performed with standardized techniques with triple centration technique using the 500-KHz VisuMax system (Carl Zeiss Meditec AG, Jena, Germany). The superior cap depth was set as 120 or 140 µm, and the length of the side cut was set to 2 mm. Once the anterior (upper) and posterior (lower) planes of the lenticule were defined, the anterior and posterior interfaces were dissected using a micropetala with a blunt circular tip and extracted with midforceps. The integrity of the lenticule was assessed subsequently.




Primary Outcome Measures :
  1. Uncorrected Distance Vision Acuity [ Time Frame: from preoperative to postoperative 6 months ]
    Uncorrected Distance Vision Acuity in logMAR scale will be compared between the two groups at each time point.

  2. Corrected Distance vision Acuity [ Time Frame: from preoperative to postoperative 6 months ]
    Corrected Distance Vision Acuity in logMAR scale will be compared between the two groups at each time point.


Secondary Outcome Measures :
  1. 1.Total higher order aberration at each time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]

    Total higher order aberrations, spherical aberrations, and coma aberrations are examined using Keratron Scout (Optikon 2000, Rome, Italy). The unit of those is "μm".

    1,2. Total higher order aberrations at each time point and change from baseline at each time point will be compared between the two groups.


  2. 2.Total higher order aberration changes from baseline at each postoperative time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]

    Total higher order aberrations, spherical aberrations, and coma aberrations are examined using Keratron Scout (Optikon 2000, Rome, Italy). The unit of those is "μm".

    1,2. Total higher order aberrations at each time point and change from baseline at each time point will be compared between the two groups.


  3. 3.Spherical aberration at each time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]
    3,4. Spherical aberrations at each time point and change from baseline at each time point will be compared between the two groups.

  4. 4.Spherical aberration changes from baseline at each postoperative time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]
    3,4. Spherical aberrations at each time point and change from baseline at each time point will be compared between the two groups.

  5. 5.Coma aberration at each time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]

    5,6. Coma aberrations at each time point and change from baseline at each time point will be compared between the two groups.

    Corneal biomechanics including deformation amplitude ratio (DA ratio), and stiffness parameter at first applanation (SP-A1) is examined using Corvis ST (Oculus, Wetzlar, Germany). The unit of SP-A1 is "mm Hg/mm", and DA ratio is unitless.


  6. 6.Coma aberration changes from baseline at each postoperative time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]

    5,6. Coma aberrations at each time point and change from baseline at each time point will be compared between the two groups.

    Corneal biomechanics including deformation amplitude ratio (DA ratio), and stiffness parameter at first applanation (SP-A1) is examined using Corvis ST (Oculus, Wetzlar, Germany). The unit of SP-A1 is "mm Hg/mm", and DA ratio is unitless.


  7. 7.Deformation amplitude ratio (DA ratio) at each time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]
    7,8 DA ratio at each time point and change from baseline at each time point will be compared between the two groups.

  8. 8.DA ratio changes from baseline at each postoperative time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]
    7,8 DA ratio at each time point and change from baseline at each time point will be compared between the two groups.

  9. 9.Stiffness parameter at first applanation (SP-A1) at each time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]
    9,10 SP-A1 at each time point and change from baseline at each time point will be compared between the two groups.

  10. 10.SP-A1 changes from baseline at each postoperative time point between the two groups. [ Time Frame: from preoperative to postoperative 6 months ]
    9,10 SP-A1 at each time point and change from baseline at each time point will be compared between the two groups.



Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.


Layout table for eligibility information
Ages Eligible for Study:   20 Years to 45 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
Criteria

Inclusion Criteria:

  1. age of 20 years or older.
  2. Myopia
  3. Who is willing to get SMILE surgery

Exclusion Criteria:

  1. severe ocular surface disease
  2. any corneal disease, cataract, glaucoma, macular disease, or previous history of intraocular or corneal surgery
  3. Patients with suspicion of keratoconus on corneal topography

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT03584555


Contacts
Layout table for location contacts
Contact: Tae-im Kim, MD +82-2-2228-3570 TIKIM@yuhs.ac

Locations
Layout table for location information
Korea, Republic of
Department of Ophthalmology, Yonsei Univeristy College of Medicine Recruiting
Seoul, Korea, Republic of, 03722
Contact: Tae-im Kim, MD    +82-2-2228-3570    TIKIM@yuhs.ac   
Sponsors and Collaborators
Yonsei University

Publications:
Layout table for additonal information
Responsible Party: Yonsei University
ClinicalTrials.gov Identifier: NCT03584555     History of Changes
Other Study ID Numbers: 4-2017-0063
First Posted: July 12, 2018    Key Record Dates
Last Update Posted: July 12, 2018
Last Verified: June 2018
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: No

Layout table for additional information
Studies a U.S. FDA-regulated Drug Product: No
Studies a U.S. FDA-regulated Device Product: No

Keywords provided by Yonsei University:
Small incision lenticule extraction
Cap thickness

Additional relevant MeSH terms:
Layout table for MeSH terms
Surgical Wound
Wounds and Injuries