Femtosecond Lenticule EXtraction
Femtosecond Lenticule EXtraction (FLEX) is a form of laser based refractive eye surgery developed by Carl Zeiss Meditec used to correct myopia, and astigmatism. Although similar to LASIK laser surgery, the intrastromal procedure is novel in that it uses a single femtosecond laser referenced to the corneal surface to cleave a very thin reticule from the corneal stroma for manual extraction. It has been described as a painless procedure. For candidates to qualify for this treatment, they have their corneal stroma thickness checked to make sure that post operative thickness won’t be too thin.
The reticule to be extracted is accurately cut to the correction prescription required by the patient using a photodisruption laser-tissue interaction. The method of extraction can be via a Lasik type flap, but more recently a flapless technique makes a small tunnel incision in the corneal periphery. (SMILE) The general term now adopted for these techniques is refractive lenticule extraction.(FLEx)
After the femtosecond laser has separated the reticule, a blunt spatula is inserted through the incision between the reticule and the stroma and carefully rotated to ensure that the reticule is completely detached prior to removal by forceps. The procedure has been described as safe and predictable in treating myopia and astigmatism. Some theoretical advantages are that the technique is minimally invasive compared to other flap based treatments and no collateral damage occurs to surrounding tissue due to the high speed of the femtosecond laser. There are limited studies on corneal wound healing and inflammatory response after this treatment has been carried out. There is a suggestion that the expression of fibronectin which is associated with wound healing is less in this method compard to femtosecond-LASIK. Because FLEx treatment is relatively new compared to other laser correction treatments, result studies are limited, but postoperative five year (SMILE) results indicate that there were no significant changes to the data obtained after six months.  In some cases post operative tear secretion and dry eye syndrome have been observed along with similar post operative complications seen in LASIK surgery.
As FLEx techniques evolve, there is a possibility that extracted reticules can be cryogenicaly preserved either for future donation, or re-implantation.Proof of concept has been carried out on primates where reticules were extracted from monkeys and allogenically transplated into other monkeys with positive results.
- Ivarsen, Anders; Hjortdal, Jesper (2014). "New Developments in the Lenticule Extraction Procedure". European Ophthalmic Review. 08 (01): 31. doi:10.17925/EOR.2014.08.01.31. ISSN 1756-1795.
- Walter Sekundo (2015-08-03). Small Incision Lenticule Extraction (SMILE): Principles, Techniques, Complication Management, and Future Concepts. Springer. p. 15. ISBN 978-3-319-18530-9.
- Ang, Marcus; Chaurasia, Shyam S.; Angunawela, Romesh I.; Poh, Rebekah; Riau, Andri; Tan, Donald; Mehta, Jodhbir S. (2012). "Femtosecond Lenticule Extraction (FLEx): Clinical Results, Interface Evaluation, and Intraocular Pressure Variation". Investigative Opthalmology & Visual Science. 53 (3): 1414. doi:10.1167/iovs.11-8808. ISSN 1552-5783.
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- Blum, Marcus; Täubig, Kathrin; Gruhn, Christin; Sekundo, Walter; Kunert, Kathleen S (2016). "Five-year results of Small Incision Lenticule Extraction (ReLEx SMILE)". British Journal of Ophthalmology. 100 (9): 1192–1195. doi:10.1136/bjophthalmol-2015-306822. ISSN 0007-1161.
- Moshirfar M, McCaughey MV, Reinstein DZ, Shah R, Santiago-Caban L, Fenzl CR (2015). "Small-incision lenticule extraction". J Cataract Refract Surg. 41 (3): 652–65. doi:10.1016/j.jcrs.2015.02.006. PMID 25804585.
- Liu R, Zhao J, Xu Y, Li M, Niu L, Liu H, Sun L, Chu R, Zhou X (2015). "Femtosecond Laser-Assisted Corneal Small Incision Allogenic Intrastromal Lenticule Implantation in Monkeys: A Pilot Study". Invest. Ophthalmol. Vis. Sci. 56 (6): 3715–20. doi:10.1167/iovs.14-15296. PMID 26047173.
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