Small incision lenticule extraction

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Small incision lenticule extraction
Specialty Ophthalmology

ReLExSmall incision lenticule extraction (SMILE), second generation of ReLEx Femtosecond lenticule extraction (FLEx), is a form of laser based refractive eye surgery developed by Carl Zeiss Meditec used to correct myopia, and cure astigmatism. Although similar to LASIK laser surgery, the intrastromal procedure uses a single femtosecond laser referenced to the corneal surface to cleave a thin lenticule from the corneal stroma for manual extraction. [1]

The lenticule to be extracted is accurately cut to the correction prescription required by the patient using a photodisruption laser-tissue interaction. [2] The posterior intrastromal plane is created first and the anterior plane second. To allow better separation, the two lenticule faces are cut by the laser head moving in a spiral fashion - conventionally outside in for the posterior face and respectively inside out for the anterior one. The minimum lenticule edge thickness is usually set at 15 µm, to avoid the risk of lenticule rupturing during detachment and subsequent extraction. [3] 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 layer. [4] One conspicuous difference between SMILE and LASIK is the size and shape of the corneal incision. In LASIK, the surgeon performs a 270-degree, 20 mm long incision, while in SMILE the so-called "side cap cut", which is the incision through which the surgeon extracts the lenticule, is usually about 4 mm long. [5] Currently in the US the procedure is only approved for nearsightedness, but is used for hypermetropia too in other countries. [6]

After the femtosecond laser 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. [7] 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 which is associated with wound healing is less in this method compared with femtosecond-LASIK. [2] 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. [8] In some cases post operative tear secretion and dry eye syndrome have been observed along with similar post operative complications seen in LASIK surgery. [1] [6]

As lenticule extraction techniques evolve, there is a possibility that extracted lenticules can be cryogenically preserved either for future donation, [9] or re-implantation. [1] Proof of concept has been carried out on primates where lenticules were extracted from monkeys and allogenically transplanted into other monkeys with positive results. [10]

Related Research Articles

<span class="mw-page-title-main">Farsightedness</span> Eye condition in which light is focused behind instead of on the retina

Far-sightedness, also known as long-sightedness, hypermetropia, and hyperopia, is a condition of the eye where distant objects are seen clearly but near objects appear blurred. This blur is due to incoming light being focused behind, instead of on, the retina due to insufficient accommodation by the lens. Minor hypermetropia in young patients is usually corrected by their accommodation, without any defects in vision. But, due to this accommodative effort for distant vision, people may complain of eye strain during prolonged reading. If the hypermetropia is high, there will be defective vision for both distance and near. People may also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus. Newborns are almost invariably hypermetropic, but it gradually decreases as the newborn gets older.

<span class="mw-page-title-main">LASIK</span> Corrective ophthalmological surgery

LASIK or Lasik, 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, since it is in the cornea. LASIK surgery is performed by an ophthalmologist who uses a laser or microkeratome to reshape the eye's cornea in order to improve visual acuity.

<span class="mw-page-title-main">Photorefractive keratectomy</span> Refractive eye surgery procrdure

Photorefractive keratectomy (PRK) and laser-assisted sub-epithelial keratectomy (LASEK) are laser eye surgery procedures intended to correct a person's vision, reducing dependency on glasses or contact lenses. LASEK and PRK permanently change the shape of the anterior central cornea using an excimer laser to ablate a small amount of tissue from the corneal stroma at the front of the eye, just under the corneal epithelium. The outer layer of the cornea is removed prior to the ablation.

<span class="mw-page-title-main">Eye surgery</span> Surgery performed on the eye or its adnexa

Eye surgery, also known as ophthalmic surgery or ocular surgery, is surgery performed on the eye or its adnexa. Eye surgery is part of ophthalmology and is performed by an ophthalmologist or eye surgeon. The eye is a fragile organ, and requires due care before, during, and after a surgical procedure to minimize or prevent further damage. An eye surgeon is responsible for selecting the appropriate surgical procedure for the patient, and for taking the necessary safety precautions. Mentions of eye surgery can be found in several ancient texts dating back as early as 1800 BC, with cataract treatment starting in the fifth century BC. It continues to be a widely practiced class of surgery, with various techniques having been developed for treating eye problems.

<span class="mw-page-title-main">Radial keratotomy</span> Refractive surgical procedure to correct myopia (nearsightedness

Radial keratotomy (RK) is a refractive surgical procedure to correct myopia (nearsightedness). It was developed in 1974 by Svyatoslav Fyodorov, a Russian ophthalmologist. It has been largely supplanted by newer, more accurate operations, such as photorefractive keratectomy, LASIK, Epi-LASIK and the phakic intraocular lens.

<span class="mw-page-title-main">Refractive surgery</span> Surgery to treat common vision disorders

Refractive surgery is an 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 (keratomileusis), lens implantation or lens replacement. The most common methods today use excimer lasers to reshape the curvature of the cornea. Refractive eye surgeries are used to treat common vision disorders such as myopia, hyperopia, presbyopia and astigmatism.

<span class="mw-page-title-main">Intraocular lens</span> Lens implanted in the eye to treat cataracts or myopia

An Intraocular lens (IOL) is a lens implanted in the eye usually as part of a treatment for cataracts or for correcting other vision problems such as short sightedness and long sightedness; a form of refractive surgery. If the natural lens is left in the eye, the IOL is known as phakic, otherwise it is a pseudophakic lens. Both kinds of IOLs are designed to provide the same light-focusing function as the natural crystalline lens. This can be an alternative to LASIK, but LASIK is not an alternative to an IOL for treatment of cataracts.

<span class="mw-page-title-main">Phakic intraocular lens</span> Lens implanted in eye in addition to the natural lens

A phakic intraocular lens (PIOL) is an intraocular lens that is implanted surgically into the eye to correct refractive errors without removing the natural lens. Intraocular lenses that are implanted into eyes after the eye's natural lens has been removed during cataract surgery are known as pseudophakic.

<span class="mw-page-title-main">Astigmatism</span> Type of eye defect

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 night. Astigmatism often occurs at birth and can change or develop later in life. If it occurs in early life and is left untreated, it may result in amblyopia.

Epikeratophakia is a refractive surgical procedure in which a lamella of a donor cornea is transplanted onto the anterior surface of the patient's cornea. A lamellar disc from a donor cornea is placed over the de-epithelialized host cornea and sutured into a prepared groove on the host cornea. Indications include treatment of keratoconus, refractive errors like myopia and high hypermetropia including aphakia, which cannot be corrected with conservative methods.

Limbal relaxing incisions (LRI) are a refractive surgical procedure to correct minor astigmatism in the eye. Incisions part way through the cornea are made at one side or at opposite edges of the cornea, following the curve of the iris, causing a slight flattening of the cornea in that area. Because the incisions are outside of the field of view, they do not cause glare and other visual effects that result from other corneal surgeries like radial keratotomy.

Laser blended vision is a laser eye treatment which is used to treat presbyopia or other age-related eye conditions. It can be used to help people that simply need reading glasses, and also those who have started to need bifocal or varifocal spectacle correction due to ageing changes in the eye. It can be used for people who are also short-sighted (myopia) or long-sighted (hyperopia) and who also may have astigmatism.

The Alpins Method is a system to plan and analyze the results of refractive surgical procedures, such as laser in-situ keratomileus (LASIK). The Alpins Method is also used to plan cataract/toric intraocular lens (IOL) surgical procedures.

Peter S. Hersh is an American ophthalmologist, researcher, and specialist in LASIK eye surgery, keratoconus, and diseases of the cornea. He co-authored the article in the journal Ophthalmology that presented the results of the study that led to the first approval by the U.S. Food and Drug Administration (FDA) of the excimer laser for the correction of nearsightedness in the United States. Hersh was also medical monitor of the study that led to approval of corneal collagen crosslinking for the treatment of keratoconus. He was the originator, in 2015, of CTAK for keratoconus, patent holder, and co-developer.

The eye, like any other optical system, suffers from a number of specific optical aberrations. The optical quality of the eye is limited by optical aberrations, diffraction and scatter. Correction of spherocylindrical refractive errors has been possible for nearly two centuries following Airy's development of methods to measure and correct ocular astigmatism. It has only recently become possible to measure the aberrations of the eye and with the advent of refractive surgery it might be possible to correct certain types of irregular astigmatism.

Post-LASIK ectasia is a condition similar to keratoconus where the cornea starts to bulge forwards at a variable time after LASIK, PRK, or SMILE corneal laser eye surgery. However, the physiological processes of post-LASIK ectasia seem to be different from keratoconus. The visible changes in the basal epithelial cell and anterior and posterior keratocytes linked with keratoconus were not observed in post-LASIK ectasia.

<span class="mw-page-title-main">Noel Alpins</span> Australian ophthalmologist

Noel Alpins is an Australian ophthalmologist who developed the Alpins method of astigmatism analysis used in refractive, corneal, and cataract surgery, used in the research of LASIK.

PiXL is a modern non-invasive non-surgical vision correction procedure.

Contoura Vision is a topography guided laser technology used to correct refractive error and thereby decreasing or eliminating dependency on glasses or contact lenses. The technology reduces side effects linked with laser procedures like LASIK and SMILE. It was FDA approved in the US in 2016. The method provides measurement of 22,000 points as compared to 200 points provided by wave front-guided LASIK method. The imperfections in the cornea are recorded and then corrected using a laser.

Clear lens extraction (CLE), also known as refractive lensectomy, custom lens replacement (CLR) or refractive lens exchange (RLE) is a surgical procedure in which clear lens of the human eye is removed. Unlike cataract surgery, where cloudy lens is removed to treat cataract, clear lens extraction is done to surgically correct refractive errors such as high myopia. It can also be done in hyperopic or presbyopic patients who wish to have a multifocal IOL implanted to avoid wearing glasses. It is also used as a treatment for diseases such as angle closure glaucoma.

References

  1. 1 2 3 Ivarsen, Anders; Hjortdal, Jesper (2014). "New Developments in the Lenticule Extraction Procedure". European Ophthalmic Review. 08 (1): 31. doi: 10.17925/EOR.2014.08.01.31 . ISSN   1756-1795.
  2. 1 2 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.
  3. ↑ Tityal, Jeewan S. (5 September 2018). "Small incision lenticule extraction (SMILE) techniques: patient selection and perspectives". Clinical Ophthalmology. 12: 1685–1699. doi: 10.2147/OPTH.S157172 . PMC   6134409 . PMID   30233132.
  4. ↑ 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 Ophthalmology & Visual Science. 53 (3): 1414–1421. doi: 10.1167/iovs.11-8808 . ISSN   1552-5783. PMID   22323464.
  5. ↑ Stephenson, Michelle (15 April 2021). "The Current State of SMILE vs. LASIK". Review of Ophthalmology. Retrieved 2 July 2024.
  6. 1 2 "SMILE (small incision lenticle extraction)". Lasercare Eye Center.
  7. ↑ Shah R, Shah S, Sengupta S (2011). "Results of small incision lenticule extraction: All-in-one femtosecond laser refractive surgery". J Cataract Refract Surg. 37 (1): 127–37. doi:10.1016/j.jcrs.2010.07.033. PMID   21183108. S2CID   43781436.
  8. ↑ 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. PMID   26746577. S2CID   23860546.
  9. ↑ 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.
  10. ↑ 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.

low-energy SMILE, high-energy SMILE and LASIK for myopia and myopic astigmatism in the United States]

Incision Lenticule Extraction (SMILE) | Official Zeiss Publication]

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