ReLEx Small incision lenticule extraction (SMILE), second generation of ReLEx Femtosecond lenticule extraction (FLEx), is a form of laser based

refractive eye surgery Refractive eye surgery is optional eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea ( keratomile ...

developed by

Carl Zeiss Meditec Carl Zeiss Meditec AG is a multinational medical technology company and subsidiary of Carl Zeiss AG. It manufactures tools for eye examinations and medical lasers as well as solutions for neurosurgery, dentistry, gynecology and oncology. Among i ...

used to correct myopia, and cure

astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at n ...

. Although similar to

LASIK LASIK or Lasik (''laser-assisted in situ keratomileusis''), commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and an actual cure for astigmatism, sinc ...

laser surgery, the intrastromal procedure is novel in that it uses a single femtosecond laser referenced to the corneal surface to cleave a thin lenticule from the corneal stroma for manual extraction and SMILE. 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 lenticule to be extracted is accurately cut to the correction prescription required by the patient using a photodisruption laser-tissue interaction. The method of extraction was via a LASIK-type flap in ReLEx FLEx, but in SMILE a flapless technique makes a small tunnel incision in the corneal periphery, that does not (mostly) destroy Bowman's membrane. Currently in the US the procedure is only approved for nearsightedness, but is used for

hypermetropia Far-sightedness, also known as long-sightedness, hypermetropia, or hyperopia, is a condition of the eye where distant objects are seen clearly but near objects appear blurred. This blurred effect is due to incoming light being focused behind, i ...

too in other countries. After the

femtosecond laser Mode locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). A laser operated in this way is sometimes r ...

has separated the lenticule, a blunt spatula is inserted through the incision between the lenticule and the stroma and carefully rotated to ensure that the lenticule 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 with 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 Fibronectin is a high- molecular weight (~500-~600 kDa) glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins. Fibronectin also binds to other extracellular matrix proteins such as collage ...

which is associated with wound healing is less in this method compared with femtosecond-LASIK. Because SMILE treatment is relatively new compared with other laser correction treatments, result studies are limited, but postoperative five year (SMILE) outcomes indicate that the results have been stable after 5 years of follow-up. In some cases post operative tear secretion and

dry eye syndrome Dry eye syndrome (DES), also known as keratoconjunctivitis sicca (KCS), is the condition of having dry eyes. Other associated symptoms include irritation, redness, discharge, and easily fatigued eyes. Blurred vision may also occur. Symptoms range ...

have been observed along with similar post operative complications seen in LASIK surgery. As lenticule extraction techniques evolve, there is a possibility that extracted lenticules can be cryogenically preserved either for future donation, or re-implantation. Proof of concept has been carried out on primates where lenticules were extracted from monkeys and allogenically transplanted into other monkeys with positive results.

References

External links

Zeiss Official Page

Comparison of early visual outcomes after low-energy SMILE, high-energy SMILE and LASIK for myopia and myopic astigmatism in the United States

Frequently Asked Questions About Small Incision Lenticule Extraction (SMILE) , Official Zeiss Publication
Surgical procedures and techniques Ophthalmology {{surgery-stub