Journal of Refractive Surgery

Original Article Supplemental Data

Optical Quality and Intraocular Scattering After Femtosecond Laser Small Incision Lenticule Extraction

Huamao Miao, MD; Li He, MD; Yang Shen, MD; Meiyan Li, MD; Yongfu Yu, MD, MS; Xingtao Zhou, MD, PhD

Abstract

PURPOSE:

To investigate objective optical quality and changes in light scatter after femtosecond laser small incision lenticule extraction (SMILE) for moderate to high myopia correction.

METHODS:

Prospective clinical study of 66 eyes of 66 patients (23 males, 43 females) with a mean age of 28.67 ± 6.62 years, mean spherical refraction of −6.06 ± 1.57 diopters, and mean cylindrical refraction of −0.68 ± 0.46 diopters. Every patient had a 3-month follow-up after a standard SMILE procedure. An optical quality analysis system was used to measure modulation transfer function cutoff frequency (MTFcutoff), Strehl2D ratio, and objective scatter index (OSI).

RESULTS:

At 3 months postoperatively, mean spherical equivalent was 0.03 ± 0.24 diopters and corrected distance visual acuities of all patients were equal to or better than preoperative values, with a mean safety index of 1.12 ± 0.17 (range: 0.80 to 1.50) and mean efficacy index of 1.18 ± 0.21 (range: 0.80 to 1.50). Mean OSI increased from 0.75 preoperatively to 1.09 at 20 days postoperatively (P < .05), and gradually declined to 0.94 at 40 days and 0.82 at 3 months postoperatively (P > .05). MTFcutoff and Strehl2D ratio did not change significantly compared with preoperative values (P > .05). Multiple linear regression analysis revealed that preoperative OSI was significantly correlated with optical quality at 3 months. Patients with less preoperative OSI tended to acquire higher MTFcutoff (b = −8.61) and lower OSI (b = 0.65) (P < .05).

CONCLUSIONS:

SMILE had little impact on retinal image quality after myopia correction. Postoperative OSI showed a temporary increase and then returned to normal.

[J Refract Surg. 2014;30(5):296–302.]

From the Eye and ENT Hospital of Fudan University, Myopia Key Laboratory of the Health Ministry, Shanghai, China (HM, LH, YS, ML, XZ); and Sector of Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark (YY).

Supported by the National Natural Science Foundation of China (Grant No. 11074052), the Key Project of Science and Technology of Shanghai (Grant No. 11JC1402000), the Shanghai Committee of Science and Technology of Shanghai (Grant No. 12XD1401600), and the Outstanding Academic Leaders Program of Shanghai (Grant No. XBR2013098).

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

AUTHOR CONTRIBUTIONS

Conception and design (HM, XZ); data collection (HM, LH, YS, XZ); analysis and interpretation of data (HM, ML, YY, XZ); writing the manuscript (HM, LH, YY); critical revision of the manuscript (HM, YS, ML, XZ); obtained funding (XZ); supervision (XZ)

Correspondence: Xingtao Zhou, MD, PhD, Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Myopia Key Laboratory of the Health Ministry, No. 83 FenYang Road, Shanghai 200031, China. E-mail: doctzhouxingtao@163.com

Received: January 21, 2014
Accepted: February 17, 2014
Posted Online: May 02, 2014

Abstract

PURPOSE:

To investigate objective optical quality and changes in light scatter after femtosecond laser small incision lenticule extraction (SMILE) for moderate to high myopia correction.

METHODS:

Prospective clinical study of 66 eyes of 66 patients (23 males, 43 females) with a mean age of 28.67 ± 6.62 years, mean spherical refraction of −6.06 ± 1.57 diopters, and mean cylindrical refraction of −0.68 ± 0.46 diopters. Every patient had a 3-month follow-up after a standard SMILE procedure. An optical quality analysis system was used to measure modulation transfer function cutoff frequency (MTFcutoff), Strehl2D ratio, and objective scatter index (OSI).

RESULTS:

At 3 months postoperatively, mean spherical equivalent was 0.03 ± 0.24 diopters and corrected distance visual acuities of all patients were equal to or better than preoperative values, with a mean safety index of 1.12 ± 0.17 (range: 0.80 to 1.50) and mean efficacy index of 1.18 ± 0.21 (range: 0.80 to 1.50). Mean OSI increased from 0.75 preoperatively to 1.09 at 20 days postoperatively (P < .05), and gradually declined to 0.94 at 40 days and 0.82 at 3 months postoperatively (P > .05). MTFcutoff and Strehl2D ratio did not change significantly compared with preoperative values (P > .05). Multiple linear regression analysis revealed that preoperative OSI was significantly correlated with optical quality at 3 months. Patients with less preoperative OSI tended to acquire higher MTFcutoff (b = −8.61) and lower OSI (b = 0.65) (P < .05).

CONCLUSIONS:

SMILE had little impact on retinal image quality after myopia correction. Postoperative OSI showed a temporary increase and then returned to normal.

[J Refract Surg. 2014;30(5):296–302.]

From the Eye and ENT Hospital of Fudan University, Myopia Key Laboratory of the Health Ministry, Shanghai, China (HM, LH, YS, ML, XZ); and Sector of Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark (YY).

Supported by the National Natural Science Foundation of China (Grant No. 11074052), the Key Project of Science and Technology of Shanghai (Grant No. 11JC1402000), the Shanghai Committee of Science and Technology of Shanghai (Grant No. 12XD1401600), and the Outstanding Academic Leaders Program of Shanghai (Grant No. XBR2013098).

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

AUTHOR CONTRIBUTIONS

Conception and design (HM, XZ); data collection (HM, LH, YS, XZ); analysis and interpretation of data (HM, ML, YY, XZ); writing the manuscript (HM, LH, YY); critical revision of the manuscript (HM, YS, ML, XZ); obtained funding (XZ); supervision (XZ)

Correspondence: Xingtao Zhou, MD, PhD, Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Myopia Key Laboratory of the Health Ministry, No. 83 FenYang Road, Shanghai 200031, China. E-mail: doctzhouxingtao@163.com

Received: January 21, 2014
Accepted: February 17, 2014
Posted Online: May 02, 2014

Femtosecond laser small incision lenticule extraction (SMILE) is a form of “flapless” corneal refractive surgery with all-in-one technology.1,2 Its predictability, efficacy, stability, and safety in myopia correction has been proved in previous studies.1–4 Optical quality assessment following refractive surgeries is just as important and correlates to patient satisfaction. Wavefront aberration was mostly used in previous studies to assess optical quality after refractive surgeries, and higher-order aberrations (HOAs) were found to increase after SMILE surgery.1,2 Shah et al. reported that HOAs, spherical aberration, coma, and fourth order astigmatism increased 6 months after SMILE, whereas no significant change was found in trefoil.1 Sekundo et al. also found that HOAs, spherical aberration, and coma were induced after SMILE.2

It is suggested that optical quality after refractive surgery is also influenced by light scatter.5,6 A recent study reported that intraocular scattering was a reliable predictor for retinal image quality after LASIK and laser epithelial keratomileusis (LASEK).7 Therefore, intraocular scattering should be taken into consideration while characterizing optical quality. The optical quality analysis system based on the double-pass system technique is an objective and quantitative method for optical quality and intraocular scattering measurement.8–10 However, the commonly used Hartmann-Shack aberrometers did not take into account the roles of intraocular scattering and thus could overestimate the retinal image quality and provided higher modulation transfer functions (MTFs) than the double-pass device, particularly in eyes with mild to severe scattering8; the double-pass system was also reported to acquire lower MTF values than a ray-tracing wavefront sensor did due to increased scattering.7,11 The double-pass system has demonstrated good repeatability12,13 and has been used in optical quality evaluation after corneal refractive surgeries14–16 and phakic intraocular lens implantation.17,18 Yet, no studies have investigated objective optical quality together with intraocular scattering after SMILE. We quantitatively evaluated objective optical quality and intraocular scattering changes after SMILE for moderate to high myopia correction.

Patients and Methods

The study was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the Ethical Committee of the Fudan University EENT Hospital Review Board. Written informed consent was obtained from each patient after the nature and possible consequences of the study were explained.

Patients

In the prospective, non-randomized study, a total of 66 patients who underwent SMILE for treatment of myopia were evaluated with one eye of each patient chosen at random for inclusion in the statistical analysis. All SMILE procedures were conducted in the Refractive Surgery Center of the Department of Ophthalmology, Eye and ENT Hospital of Fudan University (Shanghai, People’s Republic of China) between May and June 2013.

Criteria for inclusion were: age 18 to 40 years, spherical refraction error of −3 to −9 diopters (D), astigmatism of up to −2 D, corrected distance visual acuity (CDVA) of 20/20 or better, stable refraction for 2 years prior to surgery, and no use of any kind of contact lenses within previous 2 weeks. Exclusion criteria were: any eye disease except for myopia or astigmatism, suspicion of keratectasia, a history of ocular surgery or trauma, or any systemic disease. Routine preoperative examinations of each patient were conducted to rule out contraindications for SMILE. Finally, 66 eyes of 66 myopes (23 male, 43 female) with a mean age of 28.67 ± 6.62 years (range: 18 to 40 years) were included in the study. The mean preoperative spherical equivalent (SE) of the eyes was −6.40 ± 1.60 D (range: −9.25 to −3.38 D).

Surgical Technique

The VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany) with a repetition rate of 500 kHz and a pulse energy of 130 nJ was used in the SMILE procedures for myopia correction. The same surgeon (XT Z) performed the operations on all of the patients who participated in the study.

A series of bubbles was created in a spiral fashion with a spot distance of 2 × 2 μm resulting in cleavage of the following four tissue planes: the posterior surface of the refractive lenticule, the lenticule border, the anterior surface of the refractive lenticule, and a single small 90° angled side-cut incision with a circumferential length of 2 mm in the superior position. In all cases, the intended thickness of the upper tissue arcade was 110 μm and its intended diameter was 7.5 mm, 1 mm larger than the diameter of the refractive lenticule (6.5 mm). The refractive lenticule of the intrastromal corneal tissue was dissected through the side-cut opening incision and was manually removed using forceps. The exact surgical procedure was described previously by Zhao et al.19 All procedures were performed uneventfully and no intraoperative or postoperative complications were observed. Patients wore bandage soft contact lenses (Acuvue Oasys; Johnson & Johnson, Jacksonville, FL) until the day after the operation.

Postoperatively, topical medication regimens were identical for each eye and consisted of the administration of ophthalmic solution of levofloxacin, 0.1% fluorometholone solution, and non-preservative tear supplement (carboxymethylcellulose sodium eye drops; Allergan, Inc., Irvine, CA). Evaluations performed after surgery included slit-lamp examination, objective optical quality and intraocular scattering examinations, and parameters of refractive outcomes such as manifest refraction, uncorrected distance visual acuity (UDVA), CDVA, and astigmatism. The above-mentioned parameters were evaluated in all patients before surgery and at 20 days, 40 days, and 3 months after surgery. In the 40 days’ follow-up, 4 (6.1%) patients were lost. Safety index was calculated as the ratio between the CDVA at 3 months postoperatively and the corresponding preoperative CDVA, and the efficacy index was the ratio between the postoperative UDVA at 3 months and the preoperative CDVA.

Optical Quality and Intraocular Scattering Measurement

An optical quality analysis system (OQAS II; Visiometrics, Terrassa, Spain), based on the double-pass technique, was used to measure MTF cutoff frequency (MTFcutoff, cycle per degree [cpd]), Strehl2D ratio, OQAS values (OV) at different contrasts (100%, 20%, and 9%), and the objective scatter index OSI of each eye. All measurements were conducted in mesopic conditions with a 4.0-mm artificial pupil. All procedures were conducted by an experienced technician. During the measurements, any spherical refractive error (≥ −8.00 D) was automatically corrected by the double-pass system. Spherical refractive errors exceeding −8.00 D were corrected with an external lens, as were all cylindrical errors.

The double-pass system obtains images from a point-source object reflecting on the retina. The near-infrared light point-source object consists of a laser diode (wavelength: 780 nm) coupled to an optical fiber, and the system directly computes the MTF from the acquired double-pass retinal image through Fourier transformation.8 The MTFcutoff for the double-pass instrument corresponds to a 0.01 MTF value. Strehl2D ratio is calculated in two dimensions as the ratio between the area under the MTF curve of the measured eye and that of the aberration-free eye.10,12 The Strehl2D ratio ranges from 0 to 1.0; an Strehl2D ratio of 1.0 therefore indicates a perfect optical system. The three OVs (OV100%, OV20%, and OV90%) are normalized values for the three spatial frequencies that correspond to the MTF values of optical quality at three contrast conditions commonly used in ophthalmologic practice. OV100% is the MTFcutoff frequency divided by 30 cpd and is directly related to the MTFcutoff and the patient’s visual acuity. The other two frequencies have been normalized so that the values obtained are comparable to standard decimal visual acuity values. In general, the higher the MTFcutoff, Strehl2D ratio, and OV values, the better the ocular optical quality. The system also uses the OSI to quantify intraocular scattered light. The OSI is computed as the ratio of the amount of light within an annular area between 12 and 20 minutes of arc compared to that recorded within 1 minute of arc of the central peak in the acquired double-pass image. In most studies, OSI values of close to 1.0 are usually recorded in eyes with low scattering.10,20

Statistical Analysis

All data were analyzed using SAS 9.3 statistical software (SAS Institute, Inc., Cary, NC) and reported as mean ± standard deviation. With different times for measurements as the repeated factor, parameters involving retinal image quality, intraocular scattering, and refractive outcomes were compared among different time-points using the generalized estimating equation. Least-squares means in each time point were calculated and multiple comparisons were adopted.

A Bonferroni-based adjustment was made for multiple comparisons to control the family type I error at a level of 0.05. To perform a Bonferroni correction, two methods can be used: (1) dividing the critical α value (α = 0.05) by the number of comparisons being conducted (N) to get an adjusted critical α′ value (α′ = 0.05/N), then comparing the raw P value with the adjusted critical α′ value (α′ = 0.05/N) to determine the significance; and (2) multiplying the raw P value by the number of comparisons being conducted (N) to get a modified new P′ value (P′=P*N), then comparing the modified P value with the significant level of 5% to determine the significance. For the second method, the significant level α is still 5%. In our study, we employed the second method to generate the modified P value and keep the significant level α at 5%. Then, we compared the modified P value with the significant level of 5% to determine the significance. Statistical textbooks present Bonferroni adjustment using the first method. However, the second method has a mathematically equivalent adjustment as the former.

Spearman rank correlation analysis was used to assess the relationship between the preoperative factors and postoperative optical quality values at 3 months and was expressed as a Spearman’s rank correlation coefficient. Multiple linear regression models were conducted to evaluate factors associated with optical quality parameters at 3 months. A P value of less than .05 was considered statistically significant.

Results

Safety index was 1.12 ± 0.17 (range: 0.80 to 1.50) and mean efficacy index of 1.18 ± 0.21 (range: 0.80 to 1.50) at 3 months postoperatively. Figure 1 shows postoperative UDVA and CDVA changes at 3 months. The percentage of UDVA equal to or better than 20/20 was 92.42% at 20 days, and reached 100% at 40 days (P = .003) (Figure 1A). The percentage of CDVA better than 20/20 was 28.79% preoperatively and significantly increased postoperatively, with 40.91% at 20 days, 61.29% at 40 days, and 71.21% at 3 months (Figure 1B). The mean spherical values were a bit hyperopic at 20 and 40 days compared to those at 3 months. Cylindrical diopters showed great stability at the three postoperative time points (Table 1).

(A) Uncorrected distance visual acuity and (B) corrected distance visual acuity (B) changed with time in the 3 months after the femtosecond laser small incision lenticule extraction procedure (d = days; m = months; pre = preoperative).

Figure 1.

(A) Uncorrected distance visual acuity and (B) corrected distance visual acuity (B) changed with time in the 3 months after the femtosecond laser small incision lenticule extraction procedure (d = days; m = months; pre = preoperative).

Postoperative Refractive Changesa

Table 1:

Postoperative Refractive Changes

As shown in Table 2, MTFcutoff increased (improved) at 3 months after SMILE compared to that at 20 and 40 days; no significant differences were found when each of the three time points was compared to the preoperative value. Similar trends were found in OV100% and OV20%. No significant differences were found in Strehl2D ratio and OV9% among the four time points. Initially, the OSI significantly increased after SMILE, but decreased with time.

Mean Values of Objective Optical Quality and Intraocular Scattering at Each Time Point

Table 2:

Mean Values of Objective Optical Quality and Intraocular Scattering at Each Time Point

Table A (available in the online version of this article) shows the correlations between preoperative parameters and postoperative MTFcutoff or OSI. Preoperative MTFcutoff (r = 0.32), Strehl2D ratio (r = 0.40), OV100% (r = 0.32), OV20% (r = 0.36), and OV9% (r = 0.38) showed significant positive correlation with MTFcutoff (P < .05) at 3 months. Age (r = −0.32) and preoperative OSI (r = −0.49) showed a negative correlation with postoperative MTFcutoff at 3 months. As for OSI, preoperative SE (r = −0.31), spherical diopter (r = −0.28), MTFcutoff (r = −0.41), Strehl2D ratio (r = −0.51), OV100% (r = −0.41), OV20% (r = −0.46), and OV9% (r = −0.49) showed significant negative correlation with OSI at 3 months, whereas the preoperative OSI (r = 0.63) showed positive correlation with OSI at 3 months (P < .05). Age showed a barely detectable statistically significant positive correlation with OSI at 3 months (r = 0.23).

As shown in Table 3, multiple regression models were conducted with MTFcutoff or OSI at 3 months as dependent variables. Postoperative MTFcutoff decreased as age and the preoperative OSI increased. Postoperative OSI increased as age, the absolute preoperative SE value, and the preoperative OSI increased. Gender and preoperative MTFcutoff showed no significant association with postoperative MTFcutoff or OSI in the regression models.

Preoperative Factors Associated With Optical Quality or Intraocular Scattering at 3 Months in Multiple Regression Analysis

Table 3:

Preoperative Factors Associated With Optical Quality or Intraocular Scattering at 3 Months in Multiple Regression Analysis

Discussion

Intraocular scattering plays an important role in optical quality, which might reduce the contrast of the retinal image, especially in patients with refractive medium opacity (eg, corneal dystrophy and cataract) and in patients after refractive laser surgeries.5,6,20 To our knowledge, no research had investigated intraocular scattering after SMILE, and this prospective study is the first to provide detailed information about short-term objective optical quality and intraocular scattering changes after SMILE, using the double-pass technique. At the same time, we evaluated parameters that associated with postoperative optical quality and intraocular scattering by multiple factor analyses.

The refractive outcomes are in line with previous studies.1–4 SMILE showed good safety and efficacy in correcting moderate to high myopia. All patients achieved target UDVA postoperatively, and some of the patients gained better CDVA with time. No patient experienced a decline in UDVA or CDVA. Spherical refraction was slightly hyperopic at 20 and 40 days and the cylindrical diopters were stable after surgery.

A relative small change of MTFcutoff after SMILE was found in our study, which decreased (worsened) only by 6.6% at 20 days and even increased (improved) by 3.02% at 3 months when compared to the preoperative mean value of 34.07 cpd. Previous studies reported that both photorefractive keratectomy and LASIK could result in a retinal image quality decrease 3 months postoperatively. Ondategui et al. reported that retinal image quality was similarly reduced 3 months after photorefractive keratectomy and LASIK; mean MTFcutoff decreased (worsened) by 12.67% in the photorefractive keratectomy group and by 11.75% in the LASIK group when compared to their preoperative values.14 The observed postoperative MTFcutoff decrease in our study is much less than that of photorefractive keratectomy and LASIK. The OQAS values (OV100%, OV20% and OV9%) were derived from the same MTF curve, at different spatial frequencies. SMILE had more influence on OQAS values at higher and middle contrasts, and they showed a similar evolution as MTFcutoff did. However, no significant changes were found at a low contrast of OV9%, which corresponds to the MTF value of 0.1. The Strehl2D ratio barely changed after SMILE compared to the preoperative value, with only a 3.4% decrease at 20 days and a 2.18% decrease at 3 months. Anera et al. reported that the Strehl ratio diminished 3 months after LASIK by 28.57% in the standard group and 12.9% in the Q-optimized group.15 Vilaseca et al. also found that Strehl2D ratio worsened significantly by 20% to 26% at 3 months after LASIK.16 However, in our study no significant Strehl2D ratio change was found at any time point after SMILE. The lack of MTF or Strehl2D ratio decreases at 3 months found in our study could be attributed to the small wound, in which a corneal lenticule is made by femtosecond laser and is extracted through a tiny incision of only 2 mm (without lifting a flap),1,2 and the quick recovery after SMILE.4

Because the HOAs and the intraocular scatterings are two independent factors and they both affect retinal image quality,1,2,5–7 a comprehensive assessment of optical quality after refractive surgeries needs to take into consideration the influence of intraocular scattering. A statistically significant increase in the OSI after SMILE was observed in our study. The average OSI increased by 44.00% at 20 days compared to the preoperative value (0.75); however, it gradually decreased to the preoperative level at 3 months (0.81). The highest mean OSI was 1.08 at 20 days; even so, it did not deviate much from the commonly recognized normal value range of 1.0 or more.10,20 In Ondategui et al.’s study, the OSI increased by 28.21% and 37.18% at 3 months after photorefractive keratectomy and LASIK, respectively.14 The OSI increase in our study did not last to 3 months. Haze formation and anterior keratocyte loss have been indicated as the main causes of scattering increase after excimer laser surgeries, which might be related to corneal wound healing21–24; further research is needed to explore the mechanism of temporary OSI increase after SMILE.

Age was found to be associated with postoperative MTFcutoff and OSI in multiple regression in our study models. The degrading of optical quality and increasing of intraocular light scatter with advancing age had been proved in large sample studies.10,20,25 Our results are in accordance with previous studies; after the refractive errors were corrected, older patients tended to have poorer optical quality and higher intraocular scattering. Both the single factor and multiple factor analysis showed that the preoperative SE was significantly correlated with the OSI at 3 months (the higher the SE, the higher the postoperative OSI). Significant correlations between achieved refractive correction and intraocular scattering after photorefractive keratectomy or LASIK have been reported.7,14 For example, Ondategui et al. found significant correlations between the preoperative refraction and the OSI obtained from the double-pass system 3 months after photorefractive keratectomy or LASIK.14 Lee et al. also reported significant correlations between the OSI and achieved refractive correction in LASIK and LASEK 6 months after surgery.7 We found no significant correlation between the preoperative SE and MTFcutoff at 3 months after the SMILE procedure based on data acquired from the double-pass system. The preoperative OSI also exhibited a significant correlation with postoperative optical quality in the current study. After adjustments were made for age, gender, preoperative SE, and MTFcutoff, preoperative OSI showed a great impact on MTFcutoff and OSI at 3 months postoperatively. Our results suggested that patients with lower intraocular scattering tend to have higher MTFcutoff and lower OSI after SMILE. A similar result was also reported in LASIK and LASEK that OSI was a reliable parameter in predicting MTFcutoff values.7

The 3-month follow-up results showed that SMILE had minimal negative impact on patients’ retinal image quality in moderate to high myopia correction. The postoperative OSI experienced a tendency of temporary increase and gradually declined to preoperative levels in 3 months. Despite this, the OSI fluctuations were always within normal range. In addition, patients with younger age and lower intraocular scattering will achieve better optical quality after SMILE.

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Postoperative Refractive Changesa

Parameters Preoperative 20 Days 40 Days 3 Months P
SE (D) −6.40 ± 1.60 0.10 ± 0.31 0.09 ± 0.31 0.03 ± 0.24 .37
Sphere (D) −6.06 ± 1.57 0.15 ± 0.33 0.12 ± 0.29 0.05 ± 0.25 .009
Cylinder (D) −0.68 ± 0.46 −0.09 ± 0.19 −0.04 ± 0.12 −0.05 ± 0.13 .179

Mean Values of Objective Optical Quality and Intraocular Scattering at Each Time Point

Parameters Preoperative 20 Days 40 Days 3 Months P
MTFcutoff (cpd) 34.04 ± 8.94 31.71 ± 9.56 33.27 ± 7.95 35.07 ± 8.61a,b .012
SR 0.19 ± 0.05 0.18 ± 0.06 0.18 ± 0.04 0.18 ± 0.05 .487
OV100% 1.13 ± 0.30 1.06 ± 0.32 1.11 ± 0.26 1.17 ± 0.29a,b .011
OV20% 1.10 ± 0.33 1.03 ± 0.35 1.06 ± 0.29 1.11 ± 0.30a .053
OV9% 1.09 ± 0.34 1.03 ± 0.38 1.03 ± 0.30 1.05 ± 0.32 .338
OSI 0.75 ± 0.48 1.09 ± 0.77c 0.94 ± 0.69c 0.82 ± 0.53a,b .001

Preoperative Factors Associated With Optical Quality or Intraocular Scattering at 3 Months in Multiple Regression Analysis

Parameters MTFcutoff OSI


b P b P
Age (y) −0.41 .005a 0.02 .025a
Gender −2.88 .149 0.03 .755
SE (D) 0.12 .841 −0.07 .030a
MTFcutoff (cpd) −0.06 .701 0.00 .688
OSI −8.61 .005a 0.65 < .001a

10.3928/1081597X-20140415-02

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