Journal of Refractive Surgery

Original Article Supplemental Data

Femtosecond Laser–Assisted LASIK With and Without the Adjuvant Use of Mitomycin C to Correct Hyperopia

Montserrat Garcia-Gonzalez, MD, PhD; MariLuz Iglesias-Iglesias, MD; Pilar Drake Rodriguez-Casanova, MD, PhD; Juan Gros-Otero, MD, PhD; Miguel A. Teus, MD, PhD

Abstract

PURPOSE:

To compare the visual and refractive results of femtosecond laser–assisted LASIK (FS-LASIK) with and without the adjuvant use of mitomycin C (MMC) to correct hyperopia.

METHODS:

A total of 152 consecutive hyperopic eyes were included in this retrospective, observational cohort study, comparing 76 eyes treated with FS-LASIK + MMC with 76 age- and refraction-matched eyes treated with FS-LASIK without MMC. Visual and refractive results were evaluated 1 day, 1 week, and 1, 3, 6, and 15 months postoperatively.

RESULTS:

Preoperative mean spherical equivalent was +3.27 diopters (D) versus +3.50 D in the MMC and no MMC groups, respectively (P > .05). Three months postoperatively, uncorrected distance visual acuity was significantly better in the MMC group (0.93 ± 0.2) than in the no MMC group (0.87 ± 0.2) (P = .01). The residual spherical equivalent was significantly lower in the MMC group (+0.18 ± 0.40 D) than in the no MMC group (+0.42 ± 0.50 D) (P = .01). Fifteen months postoperatively, including re-treated eyes, no significant differences were found in uncorrected distance visual acuity, corrected distance visual acuity, and residual refraction. Slightly better outcomes were found in the MMC group in terms of efficacy, safety, and predictability; however, these small differences were not statistically significant. The incidence of re-treatments during the 15-month follow-up was significantly lower in the MMC group than in the no MMC group (6.6% vs 10.5%, respectively) (P = .01).

CONCLUSIONS:

FS-LASIK with or without the intraoperative use of MMC is safe and effective to correct hyperopia. However, slightly better refractive outcomes and a lower incidence of re-treatments were observed when intraoperative MMC was used, at least in a 15-month follow-up.

[J Refract Surg. 2018;34(1):23–28.]

Abstract

PURPOSE:

To compare the visual and refractive results of femtosecond laser–assisted LASIK (FS-LASIK) with and without the adjuvant use of mitomycin C (MMC) to correct hyperopia.

METHODS:

A total of 152 consecutive hyperopic eyes were included in this retrospective, observational cohort study, comparing 76 eyes treated with FS-LASIK + MMC with 76 age- and refraction-matched eyes treated with FS-LASIK without MMC. Visual and refractive results were evaluated 1 day, 1 week, and 1, 3, 6, and 15 months postoperatively.

RESULTS:

Preoperative mean spherical equivalent was +3.27 diopters (D) versus +3.50 D in the MMC and no MMC groups, respectively (P > .05). Three months postoperatively, uncorrected distance visual acuity was significantly better in the MMC group (0.93 ± 0.2) than in the no MMC group (0.87 ± 0.2) (P = .01). The residual spherical equivalent was significantly lower in the MMC group (+0.18 ± 0.40 D) than in the no MMC group (+0.42 ± 0.50 D) (P = .01). Fifteen months postoperatively, including re-treated eyes, no significant differences were found in uncorrected distance visual acuity, corrected distance visual acuity, and residual refraction. Slightly better outcomes were found in the MMC group in terms of efficacy, safety, and predictability; however, these small differences were not statistically significant. The incidence of re-treatments during the 15-month follow-up was significantly lower in the MMC group than in the no MMC group (6.6% vs 10.5%, respectively) (P = .01).

CONCLUSIONS:

FS-LASIK with or without the intraoperative use of MMC is safe and effective to correct hyperopia. However, slightly better refractive outcomes and a lower incidence of re-treatments were observed when intraoperative MMC was used, at least in a 15-month follow-up.

[J Refract Surg. 2018;34(1):23–28.]

LASIK has been shown to be a safe, effective, and predictable procedure to correct different degrees of myopia, hyperopia, and astigmatism.1,2 However, when compared with myopic corrections, predictability for comparable hyperopic refractive errors is much poorer.3 Thus, published studies indicate a good predictability for low to moderate hyperopic corrections,2–5 up to +4.00 diopters (D) in most series, but less satisfactory results are reported in the correction of higher degrees of hyperopia.6

Although femtosecond laser–assisted LASIK (FS-LASIK) seems to achieve better refractive outcomes for the correction of hyperopia than LASIK with a mechanical microkeratome,7,8 one of the main challenges of hyperopic correction continues to be the refractive regression.4 In fact, up to 30% of eyes treated with hyperopic LASIK require an enhancement.6,9

Refractive regression after hyperopic LASIK has been related to three mechanisms. First, the mid-peripheral corneal fibers that have been ablated in hyperopic correction would expand, resulting in a progressive flattening of the steepened central cornea (“biomechanical mechanism”).10 Second, there are changes in epithelial thickness after hyperopic LASIK (ie, a paracentral epithelial thickening that would reduce some of the shape change induced by stromal tissue ablation) and a central epithelial thinning that would flatten the central corneal curvature (“epithelial mechanism”).11 Third, excimer laser ablation induces keratocyte apoptosis and activation, followed by myofibroblast proliferation resulting in stromal remodeling (“wound-healing mechanism”).12

It is well known that mitomycin C (MMC) modulates the corneal wound-healing process. Because of its cytotoxic and antiproliferative effects, MMC reduces the myofibroblast repopulation after laser ablation and, therefore, reduces the risk of postoperative corneal haze formation.13 To avoid the localized haze that sometimes develops in the area of the hinge after hyperopic LASIK, and taking into account the safety of its use in both surface ablation13,14 and LASIK,15 we began to routinely use a short application of MMC in hyperopic LASIK. Considering that MMC could also theoretically minimize the risk of having refractive regression after hyperopic LASIK, we decided to compare the visual and refractive results of FS-LASIK with and without the adjuvant use of MMC for the correction of hyperopia.

Patients and Methods

We performed a retrospective study of consecutive patients who had undergone LASIK performed with a femtosecond laser to correct hyperopia and fulfilled the inclusion/exclusion criteria, before and after the routine use of intraoperative MMC.

Inclusion criteria were hyperopia of +2.00 to +6.00 D and astigmatism up to −4.00 D. We included only patients older than 40 years, in whom no differences were found between manifest and cycloplegic refractions (ie, we did not include patients with any latent hyperopia that would jeopardize an eventual refractive regression). Moreover, the decision to include only patients older than 40 years (with presbyopia) was based on the fact that the refraction of younger patients manifesting hyperopia may be easily underestimated because this group of patients may achieve good uncorrected distance visual acuity (UDVA) as a result of the accommodative response even in the absence of full hyperopic correction.

A masked observer performed the same full preoperative examination for all patients that included measurement of the UDVA, corrected distance visual acuity (CDVA) including the manifest and cycloplegic refractions, corneal keratometry and topography (CSO; Compagnia Instrumenti Oftalmici, Florence, Italy), ultrasound corneal pachymetry (DHG 5100 contact pachymeter; DHG Technology Inc., Exton, PA), corneal specular microscopy (Topcon SP-2000P; Topcon Corporation, Tokyo, Japan), mesopic infrared pupillometry (Colvard Pupillometer; Oasis Medical Inc., Glendora, CA), slit-lamp biomicroscopy, Goldmann tonometry (CT-80; Corporation), and funduscopy.

When evaluated for surgery, we excluded patients with unstable refraction, previous ocular surgery (refractive or other surgical procedures), topographic suspicion of keratoconus, ocular disease, and systemic disease that could interfere with the wound-healing process, such as diabetes mellitus and connective tissue disorders.

All patients provided written informed consent and approval was obtained from the institutional review board of Hospital La Princesa, Madrid, Spain. The study was performed in accordance with the tenets of the Declaration of Helsinki.

Surgical Technique

Two experienced surgeons (MG-G and MAT) performed all procedures between April 2012 and April 2014. A povidone-iodine solution was applied to the skin and the conjunctiva, and a sterile surgical drape and a rigid eyelid speculum were positioned. All surgeries were performed using topical anesthesia with lidocaine 2%.

The 60-kHz IntraLase femtosecond laser (IntraLase Corp., Irvine, CA) was used to create the flap, using the following parameters: a raster pattern using a 0.9 μJ bed energy level, a 0.9 μJ side-cut energy, a spot separation of 7 μm, a 70° side cut angle, a 50° hinge angle, an attempted flap thickness of 100 μm, and a flap diameter of 9 mm.

Once the flap was created, it was raised with a spatula. The stromal bed was dried with a sponge and the ablation was performed using the Esiris Schwind Excimer Laser (SCHWIND eye-tech-solutions, Kleinostheim, Germany), with an optical zone larger than or equal to the mesopic pupillary size (mean optical zone was 7.2 ± 0.2 mm in the MMC group and 7.0 ± 0.2 mm in the no MMC group; P = .07). All treatments were conducted using a topographic-guided ablation profile that has been described as more accurate than wavefront-guided ablation for the correction of hyperopia.10

In the MMC group, once the excimer laser ablation was performed, a 7-mm round cellulose sponge soaked in MMC 0.02% was applied for 10 seconds over the ablated stroma, carefully avoiding leakage of the drug to the limbus.

In both groups, the stroma was then rinsed copiously with balanced salt solution (Alcon Laboratories, Inc., Fort Worth, TX) and the flap was gently put back in place with a cannula. At the end of the surgery, antibiotic drops (ciprofloxacin 3 mg/mL; Oftacilox; Alcon Cusí, Barcelona, Spain) and nonsteroidal anti-inflammatory drops (ketorolac trometamol 5 mg/mL; Acular; Allergan, Madrid, Spain) were instilled.

Postoperative Follow-up

Postoperatively, all patients used preservative-free artificial tears as needed and were instructed to apply topical antibiotic drops (ciprofloxacin 3 mg/mL; Oftacilox; Alcon Cusí) and steroid drops (dexamethasone alcohol 1 mg/mL; Maxidex; Alcon Cusí) four times daily during the first week postoperatively. Only artificial tears were continued thereafter as needed.

Postoperative examinations were scheduled for 1 day, 1 week, and 1, 3, 6, and 15 months postoperatively. Two experienced optometrists, masked for the type of surgery, refracted the patients at each postoperative visit. All patients were refracted in the same room with the same light adjusted to mesopic conditions. A complete ocular examination including corneal topography (CSO) and corneal specular microscopy (Topcon SP-2000P) were performed 3, 6, and 15 months postoperatively.

The criterion for enhancement was basically the presence of a residual refractive error causing patient dissatisfaction with the UDVA obtained. Re-treatments were usually performed at least 6 months after the primary procedure to ensure refractive stability.4,5

Statistical Analysis

Statview SE+Graphics software (Abacus Concept Inc., Cupertino, CA) was used for the data analysis. Statistical comparisons were made using the unpaired two-tailed Student's t test. A P value less than .05 was considered statistically significant. Although the logMAR values of all visual acuity tests were used for the statistical analyses, we converted them to the more conventional Snellen quotation (decimal scale) throughout the text using a visual acuity conversion chart. The data are expressed as the mean ± standard deviation.

Results

A total of 152 consecutive hyperopic eyes were included in the study. We compared 76 eyes treated with FS-LASIK + 0.02% MMC (MMC group) versus 76 age- and refraction-matched eyes treated with FS-LASIK without using MMC (no MMC group). Preoperative data of both groups are shown in Table 1.

Preoperative Data of the 152 Consecutive Eyes That Underwent FS-LASIK With or Without the Adjuvant Use of MMC for the Correction of Hyperopiaa

Table 1:

Preoperative Data of the 152 Consecutive Eyes That Underwent FS-LASIK With or Without the Adjuvant Use of MMC for the Correction of Hyperopia

Comparing the evolution of the postoperative UDVA between groups during the early postoperative follow-up, we found no significant differences in mean UDVA at 1 day (0.86 vs 0.85), 1 week (0.9 vs 0.88), and 1 month (0.92 vs 0.95) after the surgery in the MMC and no MMC groups, respectively. However, at the 3-month postoperative visit, the mean UDVA was significantly better in the MMC group than in the no MMC group (0.93 vs 0.87, respectively) (P = .01).

Table A (available in the online version of this article) shows the visual and refractive results 6 months after surgery in both groups. The postoperative mean UDVA was significantly better in the MMC group (0.93 ± 0.2) than in the no MMC group (0.87 ± 0.2) (P = .01). The residual spherical equivalent (SE) was significantly lower in the MMC group (+0.18 ± 0.40 D) than in the no MMC group (+0.42 ± 0.50 D) (P = .01). The efficacy index was significantly better in the MMC group (0.94 ± 0.2 vs 0.88 ± 0.2 in the MMC group vs the no MMC group, respectively) (P = .01). No significant differences were found in CDVA and the safety index between groups. Regarding predictability, 86.8% (66 eyes) in the MMC group compared to 75% (57 eyes) in the no MMC group were within ±0.50 D of emmetropia (P = .006) at 6 months postoperatively. Figure 1 presents the standard graphs for reporting refractive surgery at 6 months after the primary treatment.

6-Month Postoperative Visual and Refractive Results of the 76 Hyperopic Eyes Treated With FS-LASIK + MMC and the 76 Age- and Refraction-Matched Eyes Treated With FS-LASIK Without MMCa

Table A:

6-Month Postoperative Visual and Refractive Results of the 76 Hyperopic Eyes Treated With FS-LASIK + MMC and the 76 Age- and Refraction-Matched Eyes Treated With FS-LASIK Without MMC

Standard graphs for reporting refractive surgery at 6 months after the primary treatment. (A) Cumulative histogram of uncorrected distance visual acuity. (B) Changes in lines of corrected distance visual acuity preoperatively and 6 months postoperatively. (C1–C2) Attempted versus achieved spherical equivalent refraction scatterplots including data after all primary treatments and before enhancements. The linear regression equation and coefficient of determination (r2) are displayed. (D) Predictability. (E) Refractive astigmatism. (F1–F2) Stability of spherical equivalent refraction. All data at 1, 3, and 6 months postoperatively included all eyes after primary treatment and before enhancement. Data provided at 15 months postoperatively included all eyes after primary treatment and after enhancement when needed. UDVA = uncorrected distance visual acuity; MMC = mitomycin C; CDVA = corrected distance visual acuity; D = diopters

Figure 1.

Standard graphs for reporting refractive surgery at 6 months after the primary treatment. (A) Cumulative histogram of uncorrected distance visual acuity. (B) Changes in lines of corrected distance visual acuity preoperatively and 6 months postoperatively. (C1–C2) Attempted versus achieved spherical equivalent refraction scatterplots including data after all primary treatments and before enhancements. The linear regression equation and coefficient of determination (r2) are displayed. (D) Predictability. (E) Refractive astigmatism. (F1–F2) Stability of spherical equivalent refraction. All data at 1, 3, and 6 months postoperatively included all eyes after primary treatment and before enhancement. Data provided at 15 months postoperatively included all eyes after primary treatment and after enhancement when needed. UDVA = uncorrected distance visual acuity; MMC = mitomycin C; CDVA = corrected distance visual acuity; D = diopters

Table B (available in the online version of this article) shows the visual and refractive results 15 months after surgery in both groups (including the eyes that needed an enhancement). No significant differences were found in the final UDVA, CDVA, or the residual refraction. Slightly better visual outcomes were found in the MMC group in terms of efficacy, safety, and predictability; however, these differences did not reach statistical significance. Interestingly, the incidence of re-treatments during the 15-month postoperative follow-up was significantly lower in the MMC group than in the no MMC group (6.6% vs 10.5%, respectively) (P = .01).

Comparison Between the 15-Month Postoperative Outcomes of 76 Hyperopic Eyes Treated With FS-LASIK + MMC and 76 Age- and Refraction-Matched Eyes Treated With FS-LASIK Without Using MMCa,b

Table B:

Comparison Between the 15-Month Postoperative Outcomes of 76 Hyperopic Eyes Treated With FS-LASIK + MMC and 76 Age- and Refraction-Matched Eyes Treated With FS-LASIK Without Using MMC,

No intraoperative or postoperative complications were observed in any group. We found no significant changes in the endothelial cell count 15 months after surgery compared with the preoperative values in both groups, regardless of the use of intraoperative MMC. We found no significant difference in the endothelial cell density 15 months after surgery between the MMC and no MMC groups.

Discussion

In the current study, we found that FS-LASIK, with or without the use of intraoperative MMC, was safe and effective to correct hyperopia. However, the adjuvant use of MMC provided better visual and refractive outcomes than those obtained in the no MMC group in a 6-month follow-up. In addition, FS-LASIK + MMC significantly reduced the hyperopic regression and, subsequently, the incidence of re-treatments during the 15-month follow-up.

Although it is difficult to compare our results with the previous published studies because of variations in the range of preoperative hyperopia, follow-up periods, excimer lasers, nomogram, and microkeratomes versus femtosecond laser for flap creation, the predictability (SE ± 0.50 D) of hyperopic FS-LASIK when MMC is used seems to be significantly higher (Desai et al.4 = 42.9%; Jaycock et al.5 = 53.2%; Alió et al.6 = 70.37%; Quito et al.16 = 55.8%; Leccissotti17 = 74.3%; Plaza-Puche et al.18 = 70%; current study = 86.8% at 15 months postoperatively). In fact, the incidence of re-treatments when MMC is used seems to be remarkably lower (Llovet et al.9 = 19.2%; Plaza-Puche et al.18 = 29%; Alió et al.6 = 29.4%; current study = 6.6%).

One of the main challenges of excimer laser surgery continues to be the refractive regression, especially when correcting hyperopia. The first clinical results after hyperopic LASIK suggested that small optical zones might produce less predictable corrections due to greater regression2 and, for this reason, some authors recommended the use of larger optical zones (at least 6.25 mm) when possible.19

More recently, Kanellopoulos and Asimellis20 suggested the application of prophylactic in situ high-fluence corneal cross-linking (CXL) on the stromal bed, concurrently with the LASIK procedure (technique called “LASIKXtra”) to improve refractive stability after excimer laser surgery.21 Therefore, LASIK-Xtra seems to improve refractive and keratometric stability after myopic LASIK at 2 years of follow-up,22 and similar promising results have been reported after hyperopic LASIK.23,24 The authors hypothesized that LASIK-Xtra would act as a modulator in corneal biomechanics (ie, by increasing the corneal rigidity, it would decrease the progressive flattening of the corneas treated by hyperopic LASIK that induces the refractive regression).23 In addition, Kanellopoulos and Asimellis suggested that LASIK-Xtra would also induce changes in the postoperative epithelial remodeling25 that has also been related to refractive regression. Therefore, although LASIK-Xtra seems to reduce the mid-peripheral epithelial hyperplasia in high myopic eyes,26 no studies to date have evaluated the possible postoperative changes in epithelial thickness after hyperopic LASIK-Xtra.

Nevertheless, we think that it is important to remark that CXL also has an effect on the corneal wound-healing response. It reduces the anterior stromal keratocyte population, which is, interestingly, the same effect that is seen when MMC is applied over the ablated stromal bed.12 In fact, studies with corneal confocal microscopy have shown that the application over the ablated stromal bed of both CXL27 and MMC28,29 leads to a redistribution of the keratocyte density in different corneal layers, with a temporary decrease in the anterior stromal cells, compensated for by an increase in deeper layers, followed by a normalization of stromal keratocyte density throughout the cornea over time. For this reason, it is possible that MMC and CXL may provide better refractive results and less incidence of re-treatments when used in hyperopic LASIK for the same reason—their effect on the keratocyte density. If this hypothesis is true, it would suggest that the stromal remodeling mechanism plays an important role in the refractive stability after excimer laser surgery. For this reason, we think that LASIK-Xtra long-term results are needed to further elucidate the effect of this procedure on refractive stability after hyperopic LASIK and on corneal health. However, until these studies are performed, and based on our promising results, we recommend considering the use of MMC to improve hyperopic LASIK results as an alternative to CXL due to its safety and easy application.13,14

Although MMC is widely used in surface ablation procedures, its application in LASIK has been limited only to complicated cases (buttonholes or incomplete LASIK flaps).15,26,30 In fact, to our knowledge, ours is the first study that applied MMC over the ablated stromal bed in primary uncomplicated LASIK procedures. For this reason, we arbitrarily set the exposure time for using prophylactic MMC to just 10 seconds because it has been previously reported that short exposure times of MMC are already effective in preventing postoperative haze.13 Nevertheless, we are conscious that further studies are needed to better establish the exposure time that is the most effective in reducing refractive regression after hyperopic LASIK.

FS-LASIK performed to correct hyperopia, regardless of the use of MMC, seems to provide good visual and refractive outcomes in a 15-month follow-up. Nevertheless, hyperopic eyes treated with FS-LASIK using intraoperative MMC showed less regression and a lower incidence of re-treatments. More studies with a larger number of cases and longer follow-up are needed to further elucidate the refractive stability after hyperopic FS-LASIK.

References

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Preoperative Data of the 152 Consecutive Eyes That Underwent FS-LASIK With or Without the Adjuvant Use of MMC for the Correction of Hyperopiaa

ParameterMMC GroupNo MMC GroupP
No. of eyes7676
Age (y)44.6 ± 1.1 (41 to 55)43.6 ± 1.3 (41 to 55)> .05
Sphere (D)+3.27 ± 1.10 (+2.00 to +6.00)+3.50 ± 1.20 (+2.00 to +6.00)> .05
Cylinder (D)−1.15 ± 1.20 (0.00 to −4.00)−1.20 ± 1.30 (0.00 to −4.00)> .05
SE (D)+2.71 ± 1.30 (+2.00 to +6.25)+2.90 ± 1.10 (+2.00 to +6.25)> .05
CDVA (decimal notation)1.03 ± 0.1 (0.6 to 1.5)1.05 ± 0.1 (0.6 to 1.5)> .05
Pachymetry (μm)549.67 ± 35.9 (510 to 630)545.9 ± 38.9 (515 to 620)> .05
Mean keratometry (D)45.35 ± 1.60 (39.00 to 46.00)45.53 ± 1.80 (39.00 to 46.00)> .05
Endothelial cell count (cells/mm2)2,466.6 ± 291.42,461.4 ± 298.4> .05
Mesopic pupillary size (mm)6.5 ± 0.2 (5 to 7)6.5 ± 0.2 (5 to 7)> .05

6-Month Postoperative Visual and Refractive Results of the 76 Hyperopic Eyes Treated With FS-LASIK + MMC and the 76 Age- and Refraction-Matched Eyes Treated With FS-LASIK Without MMCa

ParameterMMC GroupNo MMC GroupP
UDVA (decimal notation)0.93 ± 0.2 (0.2 to 1.5)0.87 ± 0.2 (0.4 to 1.5).01
Sphere (D)+0.23 ± 0.60 (−0.75 to +2.00)+0.51 ± 0.70 (−0.25 to +2.75).007
Cylinder (D)−0.28 ± 0.40 (0.00 to −2.50)−0.44 ± 0.50 (0.00 to −2.25).008
SE (D)+0.18 ± 0.40 (−1.00 to +1.75)+0.42 ± 0.50 (−0.625 to +2.00).01
CDVA (decimal notation)1.05 ± 0.2 (0.4 to 1.5)1.04 ± 0.2 (0.4 to 1.5).20
Efficacy index0.94 ± 0.20.88 ± 0.2.01
Safety index1.00 ± 0.21.00 ± 0.2.10
SE ±0.50 D76.3% (58/76)57.9% (44/76).006
SE ±1.00 D90.8% (69/76)82.9% (63/76).06

Comparison Between the 15-Month Postoperative Outcomes of 76 Hyperopic Eyes Treated With FS-LASIK + MMC and 76 Age- and Refraction-Matched Eyes Treated With FS-LASIK Without Using MMCa,b

ParameterMMC GroupNo MMC GroupP
UDVA (decimal notation)0.99 ± 0.2 (0.2 to 1.5)0.98 ± 0.2 (0.4 to 1.5).20
Sphere (D)+0.21 ± 0.50 (−0.50 to +1.50)+0.42 ± 0.70 (−0.50 to +2.50).08
Cylinder (D)−0.16 ± 0.30 (0.00 to −1.75)−0.33 ± 0.50 (0.00 to −2.25).60
SE (D)+0.12 ± 0.40 (−0.625 to +1.00)+0.26 ± 0.50 (−0.75 to +2.00).09
CDVA (decimal notation)1.04 ± 0.2 (0.4 to 1.5)1.04 ± 0.2 (0.4 to 1.5).10
Mean keratometry (D)46.22 ± 1.70 (41.00 to 49.00)46.44 ± 1.80 (41.00 to 49.00).30
Endothelial cell count (cells/mm2)2,425.3 ± 278.12,436.2 ± 269.1.70
Efficacy index0.98 ± 0.10.94 ± 0.2.07
Safety index1.01 ± 0.11.00 ± 0.2.10
SE ±0.50 D85.5% (65/76)84.2% (64/76).40
SE ±1.00 D97.4% (74/76)92.1% (70/76).06
Authors

From Clínica Novovisión Madrid, Madrid, Spain (MG-G, PDR-C, MAT); Clínica Rementería, Madrid, Spain (MG-G, JG-O); Clínica Tres Torres, Madrid, Spain (MI-I); and Hospital Universitario “Príncipe de Asturias,” University of Alcalá, Alcalá de Henares, Madrid, Spain (MAT).

The authors have no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (MAT); data collection (MII); analysis and interpretation of data (MG-G, PDR-C, JG-O, MAT); writing the manuscript (MG-G); critical revision of the manuscript (MG-G, MI-I, PDR-C, JG-O, MAT); supervision (MAT)

Correspondence: Montserrat Garcia-Gonzalez, MD, PhD, Clínica Rementería, Calle Almagro 36, 28010 Madrid, Spain. E-mail: montseggonz@yahoo.es

Received: June 17, 2017
Accepted: November 09, 2017

10.3928/1081597X-20171116-01

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