Randomized, Non-inferiority Trial Comparing SMILE and LASIK

Summary

Background: Small Incision Lenticule Extraction or SMILE is a novel form of 'flapless' corneal refractive surgery that was adapted from Refractive Lenticule Extraction (ReLEx). SMILE uses only one femtosecond laser to complete the refractive surgery, potentially reducing surgical time, side effects and cost. If successful, SMILE could potentially replace the current, widely practiced Laser In-situ Keratomileusis or LASIK. The aim of this study is to evaluate whether SMILE is non-inferior to LASIK in terms of refractive outcomes at 3-months post-operatively.

Methods/ Design: Single tertiary center, parallel group, single-blinded, paired-eye design, non-inferiority, randomized controlled trial. Participants who are eligible for LASIK will be enrolled for study after informed consent. Each participant will be randomized to receive SMILE and LASIK in each eye. Our primary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (\>21 years old) with myopia (\> -3.00D) at a tertiary eye center in terms of refractive predictability at 3 months post-operatively. Our secondary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (\>21 years old) with myopia (\> -3.00D) at a tertiary eye center in terms of other refractive outcomes (efficacy, safety, higher-order aberrations) at 3 months post-operatively. Our primary outcome is refractive predictability, which is one of several standard refractive outcomes, defined as the proportion of eyes achieving a postoperative spherical equivalent (SE) within ±0.50 diopter (D) of the intended target. Randomization will be performed using random allocation sequence generated by a computer with no blocks or restrictions, and implemented by concealing the number-coded surgery within sealed envelopes until just before the procedure. In this single-blinded trial, subjects and their caregivers will be blinded to the assigned treatment in each eye.

Discussion: This novel trial will provide information on whether SMILE has comparable, if not superior, refractive outcomes compared to the established LASIK for myopia, thus providing evidence for translation into clinical practice.

Conditions

• Myopia
• Astigmatism
• Hypermetropia

Interventions

PROCEDURE

Femtosecond LASIK

LASIK consists of two steps: the first step involves the formation of a corneal flap and the second one is when the excimer ablation is performed in the corneal stromal bed. Femtosecond lasers (FL) have been widely used in LASIK surgery to fashion the corneal flap. The laser will cut a lamellar followed by a vertical corneal incision. We are able to produce a vertical cut since the Femtosecond laser can deliver laser pulses of 1 micron diameter at a preselected depth in the cornea, which then expands to 2 to 3 microns with the formation of a cavitation bubble. These pulses create micro-photodisruption of the corneal tissue by the formation of an expanding bubble of carbon dioxide and water, which in turn cleaves the tissue and creates a plane of separation. The flap is then removed to expose the stroma and the refractive treatment is done by the excimer laser over the denuded stroma.

PROCEDURE

Small incision lenticule extraction (SMILE)

Patient's eye will be centered and docked with the curved interface cone before application of suction fixation. First, the posterior surface of the refractive lenticule (spiral in), then the lenticule border is created. The anterior surface of the refractive lenticule (spiral out) is then formed which extended beyond the posterior lenticule diameter by 0.5mm to form the anterior flap and is followed by a rim cut. After the suction is released, a Siebel spatula is inserted under the flap near the hinge before the flap is seperated and reflected. The edge of the refractive lenticule is separated from the stromal bed with a sinsky hook and the posterior border of the lenticule gently separated with the Siebel spatula and removed through small incision.

Sponsors & Collaborators

• Singapore National Eye Centre

  lead OTHER_GOV

Principal Investigators

• Donald T Tan, FRCS(Ed), · Singapore National Eye Centre

• Jodhbir S Mehta, FRCS (ed) · SNEC

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Model

PARALLEL

Eligibility

Min Age

21 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2012-02-29

Primary Completion

2016-11-30

Completion

2017-09-30

Countries

• Singapore

Study Locations