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Five-year results of refractive lenticule extraction

Blum, Marcus MD; Flach, Andrea; Kunert, Kathleen S. MD*; Sekundo, Walter MD

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Journal of Cataract & Refractive Surgery: September 2014 - Volume 40 - Issue 9 - p 1425-1429
doi: 10.1016/j.jcrs.2014.01.034
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Abstract

Today, several sophisticated excimer laser systems are available for laser refractive surgery, with laser in situ keratomileusis (LASIK) being the most popular procedure.1–3 Due to continuous improvements, the correction of myopia within a wide range is considered to be safe and predictable and excimer laser–based LASIK has gained wide acceptance worldwide. The long-term results (from 6 to 10 years) are widely available.4–7

A few years ago, femtosecond laser technology entered the field of refractive surgery. A new procedure that no longer requires an excimer laser, initially called femtosecond lenticule extraction, was first reported by Sekundo et al. in 20088; subsequently, the name of the procedure was changed to refractive lenticule extraction. In refractive lenticule extraction (trademarked name ReLEx-FLEx, Carl Zeiss Meditec), both the flap and the refractive lenticule are created in a 1-step procedure using a femtosecond laser.

The first peer-reviewed publications9,10 and reports by other investigators11 spurred an interest in this new technology and procedure. As a result of continuous improvements in surgical performance, energy settings, and laser technology, lifting the flap is no longer necessary and the procedure can be performed through a small incision, a procedure called small-incision lenticule extraction.12,13

Nevertheless, the long-term stability of the procedure has not been reported. This follow-up of a prospective study that evaluated the first patients treated with refractive lenticule extraction was designed to determine the long-term results (5 years). To our knowledge, these are the first reported long-term results for this technique.

Patients and methods

The Ethics Committee, Chamber of Physicians of Thuringia, Germany, approved this study. All patients treated in the initial prospective study in 2006 and 2007 received a written invitation for a reevaluation after 5 years on a voluntary basis. All patients provided informed consent.

The refractive lenticule extraction technique has been described in detail.8,9,11,13

The following parameters were obtained at the 5-year reevaluation: uncorrected (UDVA) and corrected (CDVA) distance visual acuities using different Early Treatment Diabetic Retinopathy Study charts at each visit, objective and manifest refractions, corneal topography (Atlas, Carl Zeiss Meditec AG), pachymetry and pachymetry maps (ACMaster and Visante optical coherence tomography, Carl Zeiss Meditec AG), and Goldmann applanation tonometry. The long-term side effects and surgical complications were recorded. Because refractive lenticule extraction was a new surgical approach 5 years ago, the change in CDVA was still the most important outcome measure. To avoid a shift to hyperopia, the targeted intended correction was not set at emmetropia.

All measured data were collected on standardized study spreadsheets. Statistical analysis was performed using Excel 2011 for Mac software (Microsoft Corp.) and SPSS software (version 21, International Business Machines Corp.). The Wilcoxon signed-rank test was used to compare mean outcomes.

Results

Forty-one eyes of 22 patients were recruited and reevaluated. The mean age was 41 years (range 27 to 56 years). The minimum age in the original study was 21 years.

Safety

Figure 1 shows the Snellen lines of CDVA lost or gained over time. By 5 years, no patient had lost 2 or more lines. In 1 case (2.4%), a loss of 1 Snellen line persisted after 5 years. Figure 2 shows the CDVA values.

Figure 1
Figure 1:
Safety shown as a loss or gain in Snellen lines of the CDVA (CDVA = corrected distance visual acuity).
Figure 2
Figure 2:
Five-year postoperative CDVA (CDVA = corrected distance visual acuity).

Efficacy

Figure 3 shows the efficacy over time. One eye had a UDVA of worse than 20/40 5 years postoperatively.

Figure 3
Figure 3:
Five-year postoperative UDVA (UDVA = uncorrected distance visual acuity).

Predictability

The mean attempted correction in the overall cohort was −0.52 diopter (D) ± 0.23 (SD). Figure 4 shows the attempted versus the achieved correction in the 41 eyes after 5 years. Figure 5 shows the predictability.

Figure 4
Figure 4:
Attempted versus achieved correction 5 years postoperatively (delta = mean; SE = spherical equivalent).
Figure 5
Figure 5:
Predictability 5 years postoperatively.

Stability

The refraction was stable. The mean spherical equivalent from the start of the study to 5 years was −0.07 D (Figure 6).

Figure 6
Figure 6:
Stability of refractive outcome over the 5-year follow-up (SE = spherical equivalent).

Side Effects

All patients were treated for dry-eye symptoms within the first 3 months after surgery; none required further treatment after 3 months or reported side effects at the 5-year follow-up. No other surgery-associated pathology was recorded.

Discussion

Femtosecond laser systems are versatile tools in corneal surgery. Femtosecond laser keratomes have found their place in the refractive market as an alternative to mechanical microkeratomes.14,15 In terms of the quality of surgical outcomes and safety, femtosecond laser keratomes seem to have advantages over mechanical devices.16–18 An advanced femtosecond laser system should ideally be able to perform a rapid, 1-step refractive procedure with a reduction in possible complications.19

In this study, we performed a follow-up of an initial prospective cohort (n = 108 eyes; cohort 1) that had refractive lenticule extraction (ReLEx-FLEx) for myopia in 2006 and 2007 using the 200 kHz Visumax femtosecond laser (Carl Zeiss Meditec AG). We evaluated the 5-year follow-up data of 41 eyes (cohort 2). To confirm the representativeness of the follow-up cohort, collected data were compared with the published data of the initially treated 108 eyes. There was no difference in spherical error preoperatively or 6 months postoperatively between the 2 cohorts. The UDVA was 20/40 or better in 97% of eyes in cohort 1 and in all eyes in cohort 2. The CDVA was also similar, with 8.3% of eyes in cohort 1 and 9.8% of eyes in cohort 2 losing 1 to 2 Snellen lines and 91.6% and 90.3%, respectively, with unchanged CDVA or gaining 1 to 2 Snellen lines.

In addition to the safety of the surgery itself, 2 parameters are of prime importance for the patients: predictability and long-term stability. In LASIK, 50% to more than 90% of eyes remain within ±1.00 D of the intended correction after 6 to 10 years; the outcome is largely dependent on the degree of correction.4,20,21 In the first refractive lenticule extraction cases in 2006, predictability was not as good as that of LASIK performed during the same time period. However, because of advances in laser technology, energy settings, and laser scan patterns, the outcomes of refractive lenticule extraction have improved.12,21–23 At present, the procedure is performed with a 500 kHz Visumax femtosecond laser, which was found to cause less tissue damage and inflammation in animal studies, supporting clinical impressions.24 In the most recent studies, refractive lenticule extraction yielded better refractive outcomes than in 2006, and the outcomes are comparable to those of LASIK.11 Therefore, predictability is no longer a major concern.

Today, after the establishment of nomograms, the stability of the achieved correction with refractive lenticule extraction is better than with LASIK. In LASIK, the mean regression after 6 to 7 years is reported to range from 0.63 D to 0.97 D.5,6 In our study, the results of refractive lenticule extraction were significantly better, with a mean regression of 0.07 D over a 5-year period.

Similar to patients treated with LASIK, all refractive lenticule extraction patients were treated for dry-eye symptoms within the first 3 months after the procedure.10 No further treatment was required thereafter. This is in line with published data on corneal sensitivity; that is, postoperative corneal sensitivity is less altered after small-incision lenticule extraction than after femtosecond laser–assisted LASIK.25 In a study by Vestergaard et al.,26 the less invasive small-incision lenticule extraction seemed better at sparing the central corneal nerves than femtosecond lenticule extraction and had no significant effect on corneal sensation. In another study,27 refractive lenticule extraction led to significantly less induction of higher-order aberrations and better mesopic mid-term contrast sensitivity than wavefront-optimized femtosecond LASIK after 1 year. Therefore, late side effects do not seem to be a major problem.

In summary, these first long-term outcomes of refractive lenticule extraction show excellent stability without complications over the long term. As refractive lenticule extraction gains acceptance with the introduction of the flap-free small-incision lenticule extraction technique, new studies might ameliorate remaining concerns about stability and late complications.

What Was Known

  • Refractive lenticule extraction (ReLEx-FLEx) is an effective procedure to correct myopia.

What This Paper Adds

  • Refractive lenticule extraction refractive outcomes are comparable to LASIK outcomes.
  • After a 5-year follow-up, refractive lenticule extraction showed better stability than LASIK.

References

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