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Laser correction of vision SMILE or "Why we do SMILE"


Cornea after laser cutting

Today in the Internet space there are more and more discussions on the topic: What is the best method of laser correction? ". For a long time, I did not want to interfere with the irrelevant discussion, but after seeing the regular comments of the "crusaders against SMILE" from the clinic, who did not have the technical ability to do operations like SMILE, still could not stand it. Communicating with colleagues from Germany during one of the scientific conferences heard an interesting phrase: "the introduction of something new meets competition in three phases of development:

  1. Not given any attention, because" all the same nonsense "
  2. An active attack or denial of a competitive product is what we come across in online posts
  3. The complete calm, during which the development of its own products of this type is being carried out – so in due time the companies Alcon and Schwindt reacted, which now themselves develop technology SMILE.

Apparently this kind of errors are found not only in commercial companies, but also among individual Russian surgeons.

To begin with, the operation of Femto-LASIK is really good and for years the justified technique that I have been possessing for many years. Therefore, the question is not the confrontation of these operations, but the choice of the best method for an individual patient, depending on his age, refraction and other factors.
Being an active user of SMILE technology, I want to answer the comments of colleagues of ophthalmologists, based on the data in the peer-reviewed world scientific literature, whenever possible meta-analyzes, in which all the studies on this topic are compared.
Here are the arguments that are unreliable from the point of view The view of evidence-based medicine:

Myth 1. The risk of dry eye syndrome after SMILE surgery is not less than after Femto-LASIK, as in the SMILE process, a long-term vacuum effect occurs on the goblet cells of the conjunctiva responsible for the production of tear fluid, and nerve fibers of the cornea also damage.
] Answer: Unfortunately, you are wrong. Goblet cells of the conjunctiva are destroyed by femtosecond lasers with a conjunctive seizure zone (for example, Intralase (AMO), Wafelight (Alcon), etc.). VisuMax has a purely corneal grip (see Figure 1) and therefore can not influence conjunctival cells! Reduction of the problem with dry eye syndrome is associated with a small lateral incision. By the way, I work with 2.5mm, and not a 3mm cut – in comparison with the 20mm cut at Femto-LASIK. There are scientific works on this subject. A meta-analysis on this topic confirms the theory of denervation: in the initial period of the problem with SMILE is less. After 6 months, there is no difference between both operations, since Femto-LASIK is regenerated during this time.

Myth 2. The accuracy of correction in SMILE operation is significantly lower than with Femto-LASIK, it does not correct hyperopia, mixed astigmatism and large degrees of myopic astigmatism. The SMILE operation does not allow for personalized ablation, taking into account the individual features of the cornea.
Answer: The accuracy of correction after SMILE is not even worse than the aspherical profiles of the excimer laser. And on this topic there are already many publications that are in meta-analyzes. Despite the fact that some studies show some advantages of SMILE, and some Femto-LASIK, there is no difference in the overall comparison. I think that colleagues with this statement relied on some reviews of doctors, recently engaged in SMILE technology. They do not yet have their own nomograms for SMILE, while Femto-LASIK have been engaged for a long time. In addition, surgical skills with SMILE are much more important than with Femto-LASIK. By the way, this was also one of the factors why we decided to join the network of SMILEEYES clinics. Doctors in SMILEEYES have many thousands of experience and a huge database that we use. Moreover, the training was conducted by the pioneer of technology, Professor Walter Secundo, who himself several times a year operates in Moscow. Thus, we did not even have a single case of the need for correction. According to the literature, the need for pre-correction after SMILE is 2.2%, and after LASIK of 5 to 8%, and this is due not to the inaccuracy of Femto-LASIK (it is quite accurate), but to regression, which is greater for Femto-LASIK than for SMILE.
Colleagues are right that at the moment correction of hyperopia and mixed astigmatism for commercial purposes is not possible. In May of this year, prof. The seconds and co-authors, as well as Reinstein and co-authors, 8 presented extremely successful results of the study of correction of hypermetropia and astigmatism at the conference in Los Angeles (ASCRS = American Society of Cataract and Refractive Surgeons). Admission for commercial use is expected in 3 years after the end of the multi-centered international study under the supervision of Secundo. As for myopic astigmatism – should object to colleagues. As surgeons who do not have experience with SMILE, they are apparently not familiar with the latest publications on corneal marking for high astigmatism (Ganesh S, Brar S, presentation on APACRS 2017, also, pic.1). The clinics of SMILEEYES immediately adopted this innovation and the results are really exceptionally good.

Myth 3. In the SMILE operation, the optical zone decentration may occur more often than in the Femto-LASIK operation, and sometimes, especially when correcting for myopia of a weak degree, difficulties arise with the removal of the lenticular (lens from the optic zone of the cornea), which also has a negative effect on visual acuity after operation.
Answer: A fairy tale that when SMILE is more decentralized or worse, the alignment is just nonsense. Read the literature! Already in 2014, Lazaridis and Secundo, and then in 2015 Reinstein and co-authors showed that the skillfully conducted autocentre (the patient looks at the flashing lamp and at this time the cornea is seized) is not inferior to excimers with an active tracker like MEL 80 and even MEL 90
We in the Moscow branch of SMILEEYES (like our colleagues in European centers) perform a correction from -1.0 diopters (we had patients with -0.75) – the laser makes it possible to make such a myopia – with a phenomenal result. It all depends on the surgeon's ability to use his hands, head and laser settings.

Myth 4. After SMILE surgery, folds and opacities in the central optical zone of the cornea may appear, permanently reducing the severity and quality of vision (up to six months or more).
Answer: Colleagues are right. Of course, after miopic SMILE microfolds may appear after the surface of the "lid" after removal of the lenticule is greater than the surface of the reduced stroma of the cornea. But after LASIKe can appear not only microfolds, but even macro creases! (And they do not improve with time, so the patient should be put on the table again). Therefore, the last step in both operations is the smoothing of the surface.

Myth 5. Certain difficulties arise if necessary in the correction of the refractive effect after the operation SMILE. In such cases it is necessary to switch to Femto-LASIK or PRK technology.
Answer: At this point, colleagues contradict themselves. Praising the Femto-LASIK, they write "Certain difficulties arise if necessary in the correction of the refractive effect after the operation SMILE. In such cases it is necessary to switch to Femto-LASIK or FDC technology. " That is, as: Femto-LASIK – it's great, but if SMILE should be translated into Femto-LASIK, is that bad?
By the way, there is the possibility of pre-correction using the SMILE method – this is the regular CIRCLE module, but this is only suitable for large corrections, and for the world, in spite of almost 800,000 (!) SMILE operations performed on the fingers, count

Myth 6. And all the disadvantages of the Femto-LASIK operation, such as the impact on twilight vision and the reduction of the corneal framework properties, are inherent in the SMILE operation to almost the same extent.
Answer: As for the restrictions in the postoperative period, it completely agrees with the opinion of colleagues. There is not much difference between the two types of operation – after SMILE, one day is enough, and after Femto-LASIK it takes only two weeks. However, for active people the difference of two weeks can be significant! But the fact that the decrease in frame stability after SMILE is less, especially with large corrections, is undeniable and colleagues here are completely wrong.

Let me finish this post with a request: let's move on to the third stage of discussions (see above). SMILE is an advanced technology that has enriched the repertoire of laser-refractive surgical interventions, making them even safer and more comfortable. The question should not be that it's good, but it's bad, but that you need an individual approach. And each technique has its pros and cons. Therefore, Femto-LASIK, SMILE and even PRK (especially for refractions in the region of 1 diopter) are able to exist side by side.

Illustration 1 shows the eye right after the laser cut. Clearly visible are the impressions of the suction cone on the periphery of the cornea. Pay attention also to the marking of the axis, which allows precise correction of astigmatism of a high degree. (The illustration was given permission by Prof. V. Secundo)

Literature
1. Shen Z, Zhu Y, Song X, Yan J, Yao K. Dry Eye after Small Incision Lenticule Extraction (SMILE) versus Femtosecond Laser-Assisted in Situ Keratomileusis (FS-LASIK) for Myopia: A Meta-Analysis. PLoS One. 2016 Dec 16; 11 (12): e0168081.
2. Denoyer A, Landman E, Trinh L, Faure JF, Auclin F, Baudouin C Dry eye disease after refractive surgery: comparative outcomes of small incision lenticule extraction versus LASIK. Ophthalmology. 2015 Apr; 122 (4): 669-76.
3. Shen Z, Shi K, Yu Y, Yu X, Lin Y, Yao K. Small Incision Lenticule Extraction (SMILE) versus Femtosecond Laser-Assisted In Situ Keratomileusis (FS-LASIK) for Myopia: A Systematic Review and Meta-Analysis . PLoS One. 2016 Jul 1; 11 (7): e0158176.
4. Liu M1, Chen Y, Wang D, Zhou Y, Zhang X, He J, Zhang T, Sun Y, Liu Q. Clinical Outcomes After SMILE and Femtosecond Laser-Assisted LASIK for Myopia and Myopic Astigmatism: A Prospective Randomized Comparative Study . Cornea. 2016 Feb; 35 (2): 210-6
5. Kanellopoulos AJ Topography-Guided LASIK Versus Small Incision Lenticule Extraction (SMILE) for Myopia and Myopic Astigmatism: A Randomized, Prospective, Contralateral Eye Study. J Refract Surg. 2017 May 1; 33 (5): 306-312.
6. Lazaridis A, Droutsas K, Sekundo W. Topographic analysis of the treatment zone after SMILE for myopia and comparison to FS-LASIK: subjective versus objective alignment.J Refract Surg. 2014 Oct; 30 (10): 680-6
7. Reinstein DZ, Gobbe M, Gobbe L, Archer TJ, Carp GI.Optical Zone Centration Accuracy Using Corneal Fixation-based SMILE Compared to Eye Tracker-based Femtosecond Laser-assisted LASIK for Myopia. J Refract Surg. 2015 Sep; 31 (9): 586-92
8. Reinstein DZ, Gobbe M, Gobbe L, Archer TJ, Carp GI. Optical Zone Centration Accuracy Using Corneal Fixation-based SMILE Compared to Eye Tracker-based Femtosecond Laser-assisted LASIK for Myopia. J Refract Surg. 2015 Sep; 31 (9): 586-92
9. Donate D, Thaƫron R. Preliminary Evidence of Successful Enhancement After a Primary SMILE Procedure With the Sub-Cap-Lenticule-Extraction Technique. J Refract Surg. 2015 Oct; 31 (10): 708-10
10. Spiru B, Kling S, Hafezi F, Sekundo W.Biomechanical Differences Between Femtosecond Lenticule Extraction (FLEx) and Small Incision Lenticule Extraction (Smile) Tested by 2D-Extensometry in Ex Vivo Porcine Eyes. Invest Ophthalmol Vis Sci. 2017 May 1; 58 (5): 2591-2595
11. Kling S, Spiru B, Hafezi F, Sekundo W.Biomechanical Weakening of Different Re-treatment Options After Small Incision Lenticule Extraction (SMILE). J Refract Surg. 2017 Mar 1; 33 (3): 193-198.
12. Osman IM, Helaly HA, Abdalla M, Shousha MA Corneal biomechanical changes in eyes with small incision lenticule extraction and laser assisted in situ keratomileusis. BMC Ophthalmol. 2016 Jul 26; 16: 123