Lower Femtosecond Laser Energy Levels Lead to Better Visual Recovery After Small-incision Lenticule Extraction for Myopia

NCT03111160 | Completed

• 1 other identifier: 4-2016-0840
• Study Type: interventional
• Target: 150
• Locations: 1 country
• Sites: 1

Brief Summary

Small-incision lenticule extraction (SMILE), the most recently developed refractive surgical technique, is being performed in a growing number of cases. This intrastromal keratomileusis using only a femtosecond laser is a new procedure that extracts the refractive lenticule through a small corneal incision ranging from 2 to 5 mm, with the absence of a flap and the preservation of the anterior-most stromal lamellae and Bowman's layer (except for the region of the small incision). Many studies have demonstrated that SMILE achieved comparable or superior efficacy, safety, and predictability to femtosecond laser -assisted in situ keratomileusis (FS-LASIK) and femtosecond lenticule extraction (FLEx). However, the recovery of visual acuity in the early postoperative period after SMILE is slower, compared to other refractive surgery techniques. Therefore, adjusting energy might improve postoperative visual acuity and recovery time after SMILE. Nevertheless, the optimal parameters drawn from a well-organized randomized study have yet to be elucidated. The purpose of this study was to investigate the optimal femtosecond laser energy, with the aim of improving clinical outcomes during the early postoperative period after SMILE for the correction of myopia. To this end, we used a 500 kHz VisuMax with spot-spacing control at energy levels lower than 115 nJ, based on the previous studies. Therefore, we prospectively compared visual outcomes of two groups randomly divided by different laser energies: one underwent SMILE using lower energy levels of 100, 105, and 110 nJ (L-SMILE), while the other group underwent SMILE at energy levels conventionally used of 115 to 150 nJ (C-SMILE).

Conditions

Myopia

Keywords

Small-incision lenticule extraction; femtosecond laser; lower laser energy level; early visual recovery

Outcome Measures

Primary Outcomes (2)

• Uncorrected Distance Vision Acuity

  Uncorrected Distance Vision Acuity bya Snellen visual acuity chart

  within the first 90 days after surgery

• Corneal aberration

  Corneal aberration automatically recoreded by a wavefront analysis machine

  within the first 90 days after surgery

Secondary Outcomes (1)

• surface roughness of lenticules

  immediately after SMILE surgery

Study Arms (2)

lower energy

EXPERIMENTAL

SMILE procedure using lower energy (100, 105, and 110 nJ)

Procedure: SMILE procedure using lower energy (100, 105, and 110 nJ)

conventional energy (115 to 150 nJ)

ACTIVE COMPARATOR

SMILE procedure using conventional energy (115 to 150 nJ)

Procedure: SMILE procedure using conventional energy (115 to 150 nJ)

Interventions

SMILE procedure using lower energy (100, 105, and 110 nJ) PROCEDURE

Based on the review of literature, we regarded SMILE using energy levels of 115 nJ or higher as 'conventional' energy-SMILE (C-SMILE). Since 500kHz VisuMax femtosecond laser used in this study had a threshold photodisruption energy level of 100 nJ, lowest energy level of L-SMILE was set at 100 nJ. Because the spot distance must be changed by approximately 1 μm when laser energy changed by 50 nJ, we could set the maximum laser energy to 150 (100 + 50) nJ as highest one of C-SMILE while keeping the spot distance constant. Finally, we established two groups divided by different laser energies: L-SMILE group using lower energy levels of 100, 105, and 110 nJ, and C-SMILE group using 'conventional', not higher, energy levels of 115 to 150 nJ.

lower energy

SMILE procedure using conventional energy (115 to 150 nJ) PROCEDURE

The SMILE procedures were conducted in the Eyereum Eye Clinic (Seoul, South Korea). The target postoperative refraction was emmetropia. The surgery, using standardized techniques, was performed by an experienced surgeon (D.S.Y.K.) using the VisuMax system. The surgical parameters used during SMILE were as follows: repetition rate of 500 kHz, pulse energy 100 to 150 nJ (100, 105, and 110 nJ, L-SMILE; 115 to 150 nJ, C-SMILE), spot distance 4.5 μm (regardless of FSL energy), cap thickness 120 μm, and side-cut width 2 mm in the 12-o'clock position with an angle of 90°. After the anterior (upper) and posterior (lower) delineated plane of the intrastromal lenticule were well defined, the anterior and posterior interface were dissected with a micro-spatula with a blunt circular tip and extracted with micro-forceps. The integrity of the lenticule was also checked subsequently.

conventional energy (115 to 150 nJ)

Eligibility Criteria

• Age: 20 Years - 40 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• age of 20 years or older.
• corneal thickness of more than 500 μm
• manifest refractive sphere of -3.00 to -6.00 diopters (D)
• manifest refractive cylinder less than 6.00 D
• stable refractive error with less than a 0.50 D change in sphere and cylinder in the previous year
• corrected distance visual acuity (CDVA) of 20/20 or better in both eyes

You may not qualify if:

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

Sponsors & Collaborators

• Yonsei University: lead

Study Sites (1)

Department of Ophthalmology, Yonsei Univeristy College of Medicine

Seoul, Seoul, 03722, South Korea

Location

Related Publications (3)

• Reinstein DZ, Archer TJ, Gobbe M. Small incision lenticule extraction (SMILE) history, fundamentals of a new refractive surgery technique and clinical outcomes. Eye Vis (Lond). 2014 Oct 16;1:3. doi: 10.1186/s40662-014-0003-1. eCollection 2014.

  PMID: 26605350 BACKGROUND

• Wang JS, Xie HT, Jia Y, Zhang MC. Small-incision lenticule extraction versus femtosecond lenticule extraction for myopic: a systematic review and Meta-analysis. Int J Ophthalmol. 2017 Jan 18;10(1):115-121. doi: 10.18240/ijo.2017.01.19. eCollection 2017.

  PMID: 28149787 BACKGROUND

• Donate D, Thaeron R. Lower Energy Levels Improve Visual Recovery in Small Incision Lenticule Extraction (SMILE). J Refract Surg. 2016 Aug 1;32(9):636-42. doi: 10.3928/1081597X-20160602-01.

  PMID: 27598734 BACKGROUND

MeSH Terms

Conditions

Myopia

Condition Hierarchy (Ancestors)

Refractive Errors; Eye Diseases

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: Based on the review of literature, we regarded SMILE using energy levels of 115 nJ or higher as 'conventional' energy-SMILE (C-SMILE). Since 500kHz VisuMax femtosecond laser used in this study had a threshold photodisruption energy level of 100 nJ, lowest energy level of L-SMILE was set at 100 nJ. Because the spot distance must be changed by approximately 1 μm when laser energy changed by 50 nJ, we could set the maximum laser energy to 150 (100 + 50) nJ as highest one of C-SMILE while keeping the spot distance constant. Finally, we established two groups divided by different laser energies: L-SMILE group using lower energy levels of 100, 105, and 110 nJ, and C-SMILE group using 'conventional', not higher, energy levels of 115 to 150 nJ.

Study Record Dates

• First Submitted: March 26, 2017
• First Posted: April 12, 2017
• Study Start: November 16, 2016
• Primary Completion: January 15, 2017
• Study Completion: January 15, 2017
• Last Updated: April 12, 2017

Record last verified: 2017-04

Data Sharing

• IPD Sharing: Will not share

Locations

KR (1)