Early Changes Between Lenticule Extraction and Small-Incision Lenticule Extraction

Not Applicable

Completed

• Conditions: Myopia; Astigmatism
• Interventions: Procedure: lenticule extraction; Procedure: small-incision lenticule extraction

• Registration Number: NCT02540785
• Lead Sponsor: Sun Yat-sen University

Brief 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For both FLEx and SMILE, stromal ablation has been replaced by refractive lenticule removal.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.

Study Timeline

• Study Start: 2014-04
• Primary Completion: 2014-12
• Study Completion: 2014-12
• Study First Submitted: 2015-08-31
• Study First Submitted QC: 2015-09-01
• Study First Posted: 2015-09-04
• Status Verified: 2016-11
• Last Update Submitted: 2016-11-24
• Last Update Posted: 2016-11-28

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 41

Inclusion Criteria

• minimum age of 18 years(range from 18 year to 25 years); corneal thickness 500 μm with calculated residual stromal bed after treatment greater than 300 μm; preoperative spherical equivalent refraction between
• 2.00 diopter (D) and -6.50 D; preoperative cylindrical equivalent refraction between -0.25 D and -1.50 D; preoperative corneal curvature from 41.0 D to 46.0 D with a regular topographic pattern, verified with an Atlas topographer; monocular best corrected visual acuity of 20/20 or better and stable refractive error (less than 0.5 D change) for 24 months before surgery

Exclusion Criteria

• systemic disease that contraindicated the surgery (such as diabetes, glaucoma and systemic collagen vascular disease); corneal abnormality or disease; a history of tear supplement usage or contact lens wear during the past year

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
lenticule extraction	lenticule extraction	The patients in this group chose to receive the lenticule extraction surgery.
small-incision lenticule extraction	small-incision lenticule extraction	The patients in this group chose to receive the small-incision lenticule extraction surgery.

Primary Outcome Measures

Name	Time	Method
concentration of matrix metalloproteinase-9	up to 1month after surgery
questionnaire of ocular surface disease index	up to 1month after surgery
concentration of nerve growth factor	up to 1month after surgery
concentration of interferon-γ	up to 1month after surgery
scale of Schirmer I test	up to 1month after surgery
scale of central corneal sensitivity	up to 1month after surgery
scale of tear meniscus height	up to 1month after surgery
concentration of transforming growth factor-β1	up to 1month after surgery
scale of noninvasive tear breakup time	up to 1month after surgery
scale of corneal fluorescein staining	up to 1month after surgery
concentration of Interleukin-1α	up to 1month after surgery
concentration of tumor necrosis factor-α	up to 1month after surgery

Secondary Outcome Measures

Name	Time	Method
Correlation Between Inflammatory Mediators and Ocular Surface Changes	up to 1month after surgery