Astigmatism, Myopia
Conditions
Keywords
lenticule extraction, laser in situ keratomileusis, femtosecond laser-assisted laser in situ keratomileusis, tear, inflammatory mediators
Brief summary
To evaluate the short-term changes in ocular surface measures and tear inflammatory mediators after lenticule extraction (FLEx), laser in situ keratomileusis (LASIK) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) procedures.
Detailed description
Laser in situ keratomileusis (LASIK) with a microkeratome has been accepted wildly in the past 20 years. Gradually, laser in situ keratomileusis with a femtosecond laser-created flap (FS-LASIK)has been a popular ophthalmic procedure for the correction of refractive error. This first all-in-one FS-laser system was designed to perform the refractive lenticule extraction (ReLEx) procedures, femtosecond lenticule extraction (FLEx).They have the same feature: corneal flap. 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. This prospective clinical study is going to analyze the short-term changes in ocular surface measures and tear inflammatory mediators after FLEx, LASIK and FS-LASIK procedures.
Interventions
PROCEDURElenticule extraction
Four femtosecond incisions will be 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 is released, the flap will be opened using a thin, blunt spatula and the free refractive lenticule will be subsequently grasped with a forceps and extracted, after which the flap will be repositioned carefully.
PROCEDURElaser in situ keratomileusis
During LASIK surgery, the eye will be gently proptosed and a hinged corneal flap will be cut using a microkeratome. The flap will be lifted and the stromal bed will receive a 6 mm diameter and stroma ablation. Finally reposition the flap carefully.
PROCEDUREFS assisted laser in situ keratomileusis
Track distance and spot distance will be 3.0 μm during flap creation and 1.5 μm during flap side-cutting. The flap diameter will be 8.0 mm, and flap thickness will be set to 105 μm. Side-cut angle and hinge angle will be 90°and 50° respectively. The flaps will be created by laser scanning in spirals from the periphery to the center of the pupil. An excimer laser system will be used in the subsequent ablation of thstromal bed with a 6.0 mm optical zone. Once the excimer. ablation is completed, the flap will be repositioned in a similar fashion as in routine LASIK.
Sponsors
Sun Yat-sen University
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 31 Years
Healthy volunteers
Yes
Inclusion criteria
* minimum age of 18 years(range from 18 year to 31 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 42.0 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
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| concentration of transforming growth factor-β1 | up to 1month after surgery |
| concentration of matrix metalloproteinase-9 | up to 1month after surgery |
| scale of Schirmer I test | up to 1month after surgery |
| scale of corneal fluorescein staining | up to 1month after surgery |
| scale of noninvasive tear breakup time | up to 1month after surgery |
| questionnaire of ocular surface disease index | 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 Interleukin-1α | up to 1month after surgery |
| concentration of tumor necrosis factor-α | up to 1month after surgery |
| concentration of nerve growth factor | up to 1month after surgery |
| interferon-γ | up to 1month after surgery |
Secondary
| Measure | Time frame |
|---|---|
| Correlation between Interleukin-1α and ocular surface disease index | up to 1month after surgery |
| Correlation between tumor necrosis factor-α and ocular surface disease index | up to 1month after surgery |
| Correlation between nerve growth factor and ocular surface disease index | up to 1month after surgery |
| Correlation between interferon-γ and ocular surface disease index | up to 1month after surgery |
| Correlation between transforming growth factor-β1 and ocular surface disease index | up to 1month after surgery |
| Correlation between matrix metalloproteinase-9 and ocular surface disease index | up to 1month after surgery |
| Correlation between Interleukin-1α and corneal fluorescein staining | up to 1month after surgery |
| Correlation between tumor necrosis factor-α and corneal fluorescein staining | up to 1month after surgery |
| Correlation between nerve growth factor and corneal fluorescein staining | up to 1month after surgery |
| Correlation between interferon-γ and corneal fluorescein staining | up to 1month after surgery |
| Correlation between transforming growth factor-β1 and corneal fluorescein staining | up to 1month after surgery |
| Correlation between matrix metalloproteinase-9 and corneal fluorescein staining | up to 1month after surgery |
Countries
China
Outcome results
None listed