What are the best procedures for low-to-moderate myopia?
Journal of Cataract and Refractive Surgery Symposium debates merits of LASIK, SMILE and phakic IOL implantation
Dan Z Reinstein MD
LASIK, Small Incision Lenticule Extraction (SMILE), and phakic IOL implantation can all provide safe and effective correction for low-to-moderate myopia, but which is best?
In the Journal of Cataract and Refractive Surgery Symposium during the XXXIV Congress of the ESCRS in Copenhagen, Denmark proponents of each procedure outlined why they considered it the treatment of choice.
Explaining his preference for SMILE, Dan Z Reinstein MD MA(Cantab) FRCOphth first acknowledged that LASIK is an excellent procedure, particularly for treating low-to-moderate myopia, so this debate is akin to comparing a Ferrari with an Aston Martin. He noted that in early experience, the results achieved with SMILE did not match up to LASIK outcomes, but this was to be expected given that LASIK is a mature, highly developed and highly sophisticated procedure with over 51 million performed worldwide to date. More recent data, however, show that SMILE has “come of age”, delivering efficacy and safety comparable to LASIK.
Dr Reinstein supported his comments with a review of SMILE outcomes data and discussed other advantages. Presenting his personal data for a series of more than 100 eyes that underwent SMILE to correct -1.00D to -3.50D myopia, published in the Journal of Refractive Surgery(refs), Dr Reinstein reported that at 12 months postoperatively, uncorrected distance visual acuity (UDVA) was 20/20 in 96% of eyes, corrected distance visual acuity (CDVA) was unchanged or improved from baseline in 91% of eyes, and no eyes lost ≥2 lines of CDVA. Refractive results, including cylinder correction, are stable and accurate—84% of eyes were within ±0.5D of target, reported Dr Reinstein, London Vision Clinic, London, UK.
Comparing SMILE and LASIK, Dr Reinstein pointed out that SMILE avoids the practical disadvantages associated with using an excimer laser and demonstrated published evidence of an advantage when it comes to corneal biomechanics. (1,2,3)
“With SMILE, we can treat with a larger optical zone, leave the cornea stronger and still induce less spherical aberration. And, the spherical aberration is more predictable because the biomechanics are more predictable,” he explained, “this is why talking about wavefront guided treatment in these eyes is no longer necessary, as very few eyes actually have high levels of aberrations preoperatively: the name of the game is to reduce the induction of aberrations.”
In addition, the corneal nerve plexus is better preserved with SMILE versus LASIK.
By one or two months after SMILE, corneal sensitivity is almost back to normal, and this translates into less aggravation of tear dysfunction, Dr Reinstein said.
“Femtosecond laser-assisted LASIK has been, is, and will remain the procedure of choice for correcting low-to-moderate myopia because it is the most precise and most predictable option,” said Julian Stevens, MD, Moorfields Eye Hospital, London, UK.
Reviewing 25 years of experience with excimer laser eye surgery at Moorfields Eye Hospital, he demonstrated how refractive outcome predictability has continuously improved as a consequence of progressive refinements in technique and technology, and he showed data demonstrating better predictability with wavefront-guided LASIK compared with SMILE.
Although with nomogram refinements, SMILE is providing 20/20 UCVA outcomes that are comparable to those achieved with LASIK, visual recovery is faster after LASIK and wavefront-guided LASIK provides better control of higher order aberrations, Dr Stevens said.
Discussing corneal biomechanics, Dr Stevens noted that changes occur after both LASIK and SMILE.
“The changes associated with the two procedures are different. Whether the difference makes a difference and which is better is still unknown,” he said.
Dr Stevens also raised concern about the learning curve for SMILE, noting it can be a problem for surgeons who are not familiar with the proprietary femtosecond laser used to perform SMILE and particularly for achieving good centration.
“Many of my colleagues at Moorfields found SMILE was a difficult procedure to master. SMILE remains interesting, but LASIK is the benchmark,” he said.
Erik Mertens MD, explained why he considers phakic IOL implantation with the EVO+ Visian ICL (Staar) the procedure of choice for treating low-to-moderate myopia.
“The EVO+ Visian ICL provides safe, effective, predictable, and stable correction, but it is also reversible. Furthermore, with its extended optic, the latest version of the ICL provides superior quality of vision compared with LASIK,” he said.
“In addition, there are no dry eye issues with the phakic IOL, and it leaves the cornea and crystalline lens untouched. Therefore, patients needing cataract surgery later in life remain candidates for premium IOLs and will have predictable power calculations and high quality of vision.”
Dr Mertens, Medipolis Eye Centre, Antwerp, Belgium, acknowledged the criticisms that surround the safety of ICL implantation. These include the potential for causing endophthalmitis because it is intraocular surgery and concerns about cataract induction and IOP elevation.
Addressing these issues, Dr Mertens reviewed strategies for preventing endophthalmitis and cited a paper showing that it is a very rare event (0.016% among 17,954) and can be managed to achieve a good outcome. Noting that in its early days, the ICL was called the “Instant Cataract Lens”, Dr. Mertens reported that in 306 eyes he has followed for up to 3 years after implanting the prior version of the ICL (V4c, EVO Visian ICL), he has encountered no eyes with cataract nor any IOP spikes.
“Since 2012 with the introduction of the V4c, iridectomy or laser iridotomy are no longer needed when implanting the ICL,” he added.
1. Reinstein DZ, Archer TJ, Randleman JB. Mathematical Model to Compare the Relative Tensile Strength of the Cornea After PRK, LASIK, and Small Incision Lenticule Extraction. J Refract Surg. 2013;29:454-460.
2. Sinha Roy A, Dupps WJ, Jr., Roberts CJ. Comparison of biomechanical effects of small-incision lenticule extraction and laser in situ keratomileusis: finite-element analysis. J Cataract Refract Surg. 2014;40:971-980.
3. Mastropasqua L, Calienno R, Lanzini M, Colasante M, Mastropasqua A, Mattei PA, Nubile M. Evaluation of corneal biomechanical properties modification after small incision lenticule extraction using scheimpflug-based noncontact tonometer. Biomed Res Int. 2014;2014:290619.