Comparison of the Early Clinical Outcomes between Combined SMILE and Collagen Cross-linking versus SMILE

Buki Kim; Sujoung Mun; Hyuntae Choi; Younghoon Yang; Youngtaek Chung

doi:10.3341/jkos.2017.58.10.1122

Journal List > J Korean Ophthalmol Soc > v.58(10) > 1010644

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Kim, Mun, Choi, Yang, and Chung: Comparison of the Early Clinical Outcomes between Combined SMILE and Collagen Cross-linking versus SMILE

Original Article

J Korean Ophthalmol Soc 2017;58(10):1122-1130.

Published online: 25 September 2017

DOI: https://doi.org/10.3341/jkos.2017.58.10.1122

Comparison of the Early Clinical Outcomes between Combined SMILE and Collagen Cross-linking versus SMILE

Buki Kim, MD, Sujoung Mun, MD, PhD, Hyuntae Choi, MD, Younghoon Yang, MD, Youngtaek Chung, MD, PhD

Onnuri Smile Eye Clinic, Seoul, Korea

Address reprint requests to Youngtaek Chung, MD, PhD Onnuri Smile Eye Clinic, #Gangnam-daero 65 gil, Seocho-gu, Seoul 06614, Korea Tel: 82-2-6913-0000, Fax: 82-2-532-5406 E-mail: ytchungc@daum.net

Received 10 August 2017 Revised 25 August 2017 Accepted 21 September 2017

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To compare the clinical outcome of combined small incision lenticule extraction and collagen cross-linking (SMILE Xtra) with SMILE.

Methods

This study included 30 eyes from 15 patients who had undergone SMILE Xtra and a random sample of 30 eyes from 15 patients receiving SMILE alone during the same period. We obtained the following parameters from all patients: uncorrected (UDVA) and corrected distance visual acuity (CDVA), spherical equivalent (SE), efficacy and safety index, and corneal high-or-der aberrations.

Results

The SMILE Xtra group had higher preoperative SE and thinner central corneal and residual stromal bed thickness and optic zone diameter compared to the control group (p < 0.001). At 6 months, there was no significant difference in UDVA or CDVA between the two groups. The efficacy indices were 0.97 ± 0.16 and 1.05 ± 0.17 in the SMILE Xtra and control groups, re-spectively (p = 0.044), and there was no significant difference in safety index between the two groups during the follow-up period. Total corneal high-order aberrations numbered 2.59 ± 0.56 and 2.02 ± 0.41 in the SMILE Xtra and control groups, respectively (p <0.001), and there was significant increase in spherical aberration and horizontal corneal aberration in both groups compared to preoperative results. Corneal haze was observed in 20% of eyes in the SMILE Xtra group, and no complication such as corneal ectasia was observed during the follow-up period.

Conclusions

SMILE Xtra had good early clinical outcome compared to SMILE alone. It appears that SMILE Xtra can be a good modality when the cornea is thin or SE is high. However, postoperative corneal haze should be considered.

Keywords: Cross linking, Small incision lenticule extraction, Small incision lenticlue extraction (SMILE), SMILE Xtra

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Figure 1.

Refractive outcomes for small incision lenticlue extraction (SMILE) and SMILE Xtra at 6 months postoperatively. Percentages of eyes within different diopter ranges of the intended correction in spherical equivalent refraction in both groups.

Figure 2.

Predictability of spherical equivalent correction at 6 months, in (A) SMILE Xtra group and (B) SMILE alone group. Both groups showed a high level of refractive predictability. SMILE = small incision lenticlue extraction.

Figure 3.

Stability of spherical equivalent refraction in both groups after surgery. In group B, spherical equivalent was stable for 6 months after the surgery, but over time, spher-ical equivalent was incrased in group A.

Figure 4.

Change in corrected distance visual acuity (CDVA). Gain and loss in Snellen lines of both groups 6 months postoperatively.

Figure 5.

Anterior segment photograph of the patient who has Grade 0.5 corneal haze after SMILE Xtra. The cornea has faint hazziness at center, but the patient dose not complained any clinical symptoms. SMILE = small incision lenticlue extraction.

Figure 6.

Anterior segment optical coherence tomography 6 months postoperatively. Hyper-reflection line is seen faintly (arrows). The depth of demarcation line was 210 μ m (green line).

Table 1.

Preoperative demographics

	SMILE Xtra	SMILE alone	p-value^*
Age (years)	27.07	27.47	N/A
Gender (male) (n, %)	9 (60)	5 (33.3)	N/A
Sphere (diopter)	–6.44 ± 2.07	–4.42 ± 1.67	<0.001
Cylinder (diopter)	–1.24 ± 0.85	–1.22 ± 0.84	0.537
Spherical equivalent (diopter)	–7.06 ± 2.17	–5.03 ± 1.78	<0.001
Flat sim K (diopter)	42.76 ± 1.35	42.25 ± 1.13	0.247
Steep sim K (diopter)	44.43 ± 1.90	44.06 ± 1.43	0.214
Central corneal thickness (μ m)	515.03 ± 23.79	544.87 ± 26.46	<0.001
Planned residual stromal bed (μ m)	281.43 ± 24.29	328.27 ± 33.69	<0.001
Scotopic pupil size (mm)	6.24 ± 0.71	6.39 ± 0.59	0.720
Intended optic zone (mm)	6.18 ± 0.25	6.47 ± 0.14	<0.001

Values are presented as mean ± SD unless otherwise indicated.

N/A = not applicable; sim K = simulated keratometry.

^* p-valued on Mann-Whitney U-test.

Table 2.

Comparison of uncorrected and corrected distance visual acuity of both groups

		POD
		1 week	1 month	3 months	6 months
UDVA (logMAR)	SMILE Xtra	–0.03 ± 0.05	–0.05 ± 0.07	–0.06 ± 0.05	–0.06 ± 0.04
	SMILE alone	–0.06 ± 0.06	–0.09 ± 0.05	–0.08 ± 0.04	–0.09 ± 0.05
	p-value^*	0.091	0.219	0.217	0.095
CDVA (logMAR)	SMILE Xtra	–0.04 ± 0.05	–0.06 ± 0.06	–0.08 ± 0.05	–0.08 ± 0.06
	SMILE alone	–0.05 ± 0.05	–0.09 ± 0.04	–0.10 ± 0.05	–0.10 ± 0.05
	p-value^*	0.874	0.171	0.344	0.146

Values are presented as mean ± SD unless otherwise indicated.

POD = postoperative day; UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity.

^* p-valued on paired t-test.

Table 3.

The efficacy indices (postoperative UDVA/preoperative CDVA) and the safety indices (postoperative CDVA/preoperative CDVA) of both groups

		POD
		3 months	6 months
Efficacy index	SMILE Xtra	0.97 ± 0.13	0.97 ± 0.16
	SMILE alone	1.01 ± 0.14	1.05 ± 0.17
	p-value^*	0.249	0.044
Safety index	SMILE Xtra	1.01 ± 0.19	1.01 ± 0.21
	SMILE alone	1.08 ± 0.17	1.09 ± 0.20
	p-value^*	0.180	0.102

Values are presented as mean ± SD unless otherwise indicated.

UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; POD = postoperative day.

^* p-valued on Mann-Whitney U-test.

Table 4.

Preoperative and 6-month postoperative corneal aberrations measured by Galilei®

	Preoperative			6-month postoperative			Difference pre/post p-value^†
	SMILE Xtra	SMILE alone	p-value^*	SMILE Xtra	SMILE alone	p-value^*	SMILE Xtra	SMILE alone
RMS total	1.84 ± 0.76	2.1 ± 0.9	0.287	2.59 ± 0.56	2.02 ± 0.41	<0.001	<0.001	0.307
Vertical Coma, Z₃⁻¹	–0.01 ± 0.15	–0.06 ± 0.34	0.739	0.02 ± 0.32	–0.02 ± 0.31	0.889	0.447	0.421
Horizontal Coma, Z₃¹	0.01 ± 0.19	0.05 ± 0.38	0.371	–0.22 ± 0.3	–0.16 ± 0.32	0.409	<0.001	<0.001
Vertical Trefoil, Z₃⁻³	–0.13 ± 0.12	–0.03 ± 0.22	0.133	–0.07 ± 0.21	–0.08 ± 0.19	0.827	0.073	0.352
Oblique Trefoil, Z₃³	–0.03 ± 0.19	–0.07 ± 0.34	0.222	–0.05 ± 0.23	–0.02 ± 0.15	0.161	0.476	0.280
Spherical aberration, Z₄⁰	0.22 ± 0.1	0.22 ± 0.1	0.610	0.52 ± 0.2	0.32 ± 0.12	<0.001	<0.001	0.001

Values are presented as mean ± SD unless otherwise indicated.

RMS = root mean square.

^* p-valued on Mann-Whitney U-test

^† p-valued on paired t-test.

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