VisuMax Femtosecond Laser Small Incision Lenticule Extraction for the Correction of High Myopia
Lead SponsorLondon Vision Clinic
The purpose of this study is to validate the safety and effectiveness of treating myopia (short-sightedness) higher than -10D using small incision lenticule extraction (SMILE) with the VisuMax femtosecond laser.
Laser refractive surgery (LASIK and PRK) has been established for 25 years to treat myopia (short-sightedness). Over this time, the technology has been significantly improved to enable safe treatment of myopia up to -15D. Improvements including changing the shape of the lens of corneal tissue removed to better match the natural shape, and increasing the diameter of the applied correction to cover larger pupil sizes, have greatly reduced side-effects such as night vision glare and halos. Similarly, safety has been improved by using a laser (femtosecond laser) to create the corneal flap rather than a blade (known as a microkeratome), meaning that the cornea is reliably left with more than the safe amount of tissue.
In 2006, a new method of laser refractive surgery was introduced, small incision lenticule extraction (SMILE), which provides a minimally invasive keyhole method as it avoids the need to create a flap. In SMILE, a single laser (femtosecond laser) is used to make two curved cuts inside the cornea (without breaching the outside) that separate the lens of tissue that needs removing to focus the vision. This lens of tissue is removed in once piece (rather than evaporated as in LASIK) through a small 2mm wide tunnel to the surface.
SMILE has been used to treat short-sightedness up to -10D for more than 200,000 procedures worldwide and has been shown to achieve similar results to LASIK. However, because no flap is needed, this upper part of the cornea can also contribute strength, meaning that the cornea is stronger after SMILE than after LASIK. It is also expected that the accuracy for higher corrections using SMILE would be better than LASIK because the potential inaccuracies associated with excimer lasers (used in LASIK) are eliminated. This study will investigate the results of SMILE for myopia above -10D.
The VisuMax femtosecond laser is used to create two interfaces that define a refractive lenticule of stromal tissue and a 2mm wide tunnel to connect the upper layer to the corneal surface. The lenticule is manually dissected and removed through the small 2mm incision without the need to create a flap as in LASIK.
Tobramycin and dexamethasone (Tobradex) eye drops will be used four times a day for 1 week after the procedure
Ofloxacin (Exocin) eye drops will be used four times a day for 1 week after the procedure
Proxymetacaine 0.5% eye drops will be used as an anaesthetic during the procedure
Oxybuprocaine 0.4% eye drops will be used as an anaesthetic during the procedure
Patients with high myopia will undergo a SMILE procedure to correct their refraction. Proxymetacaine 0.5% and Oxybuprocaine 0.4% will be used as anaesthetic during the procedure. Tobramycin and dexamethasone, and ofloxacin will be used four times a day for one week after the procedure.
Inclusion Criteria: Only patients who are medically suitable for corneal refractive surgery can be included in the study. Subjects should be 21 years of age or older Eyes with high myopia spherical equivalent between -9.00 D up to -14.00 D, with cylinder up to 7.00 D The corrected distance visual acuity will be 20/40 or better in each eye pre-operatively Calculated sub-lenticule thickness (SLT) ≥220 µm Calculated total uncut stromal thickness (TUST) ≥300 µm Contact lens wearers must stop wearing their contact lenses at least four weeks per decade of wear before baseline measurements in case of hard contact lenses and one week before baseline measurements in case of soft contact lenses. Patient will be able to understand the patient information and willing to sign an informed consent Patient will be willing to comply with all follow-up visits and the respective examinations as specified in the flow-chart Exclusion Criteria: Previous intraocular or corneal surgery of any kind on the eye being treated Patient not being able to lie flat in a horizontal position Patient not being able to tolerate local or topical anesthesia Autoimmune diseases Sicca syndrome, dry eye Herpes viral (herpes simplex) infections Herpes zoster Diabetes Pregnant or nursing women (or who are planning pregnancy during the study) Patients with a weight of > 135 kg Any residual, recurrent or acute ocular disease or abnormality of the eye, e.g. Cataract Suspected glaucoma or an intraocular pressure > 21 mm of Hg Corneal disease Corneal thinning disorder, e.g. keratoconus, Pellucid marginal corneal degeneration Dystrophy of the basal membrane Corneal oedema Exudative macular degeneration Infection Any residual, recurrent, or active abnormality of the cornea to be treated, e.g. Existing corneal implant Corneal lesion Unstable refraction Connective tissue disease Dry eye