Small-incision lenticule extraction versus femtosecond lenticule extraction for myopic: a systematic review and Meta-analysis

Abstract

Aim: To examine differences in efficacy, accuracy, safety, aberrations and corneal biomechanical between Small incision lenticule extraction (SMILE) and femtosecond lenticule extraction (FLEx) for myopia.

Methods: Comprehensive studies were conducted on the PubMed, MEDLINE, EMBASE, and Cochrane Controlled Trials Register before 31 July, 2015. Meta-analyses were performed on the primary outcomes [loss of ≥2 lines of corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) ≥20/20, spherical equivalent (SE) within ±0.50 diopters (D), final refractive SE], secondary outcomes were high-order aberrations (HOAs) and corneal biomechanical [central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF)].

Results: Seven trials describing a total of 320 eyes with myopia were included in this Meta-analysis. No significant differences were found in the efficacy [UDVA weighted mean difference (WMD) -0.01; 95%CI: -0.04 to 0.01; P=0.37, UDVA ≥20/20, OR 1.49; 95%CI: 0.78 to 2.86; P=0.23], accuracy (SE WMD -0.03; 95%CI: -0.12 to 0.07; P=0.58, SE within ±0.5 D OR 1.25; 95%CI: 0.34 to 4.65; P=0.74), HOAs (WMD -0.04; 95%CI: -0.09 to 0.01; P=0.14) and CCT WMD 1.83; 95%CI: -7.07 to 10.72; P=0.69, CH WMD -0.01; 95%CI: -0.42 to 0.40; P=0.97, CRF WMD 0.17; 95%CI: -0.33 to 0.67; P=0.50) in the last fellow-up. But for safety, FLEx may achieve fewer CDVA lost two or more two lines (OR 11.11; 95%CI: 1.27 to 96.86; P=0.03) than SMILE, however CDVA (WMD 0.00; 95%CI: -0.03 to 0.02; P=0.77) is similar.

Conclusion: SMILE and FLEx are comparable in terms of both efficacy, accuracy, aberrations and corneal biomechanical measures in the follow-up, but FLEx seems to be better in safety measures. The results should be interpreted cautiously since relevant evidence is still limited, although it is accumulating. Further large-scale, well-designed randomized controlled trials are urgently needed.

Keywords: Meta-analysis; femtosecond lenticule extraction; myopia; small-incision lenticule extraction.

Figures

Figure 1. The flow chart of selection of trails.

Figure 2. Forest plot of logMAR UDVA after SMILE vs FLEx

UDVA: Uncorrected distance visual acuity; SMILE: Small incision lenticule extraction; FLEx: Femtosecond lenticule extraction; df: Degrees of freedom; Chi2: Chi-square test; I2: Extent of inconsistency; Z: Overall effect.

Figure 3. Forest plot of proportion of eyes with UDVA ≥20/20 after SMILE vs FLEx

UDVA: Uncorrected distance visual acuity; SMILE: Small incision lenticule extraction; FLEx: Femtosecond lenticule extraction; df: Degrees of freedom; Chi2: Chi-square test; I2: Extent of inconsistency; Z: Overall effect.

Figure 4. Forest plot of logMAR CDVA after SMILE vs FLEx

UDVA: Uncorrected distance visual acuity; SMILE: Small incision lenticule extraction; FLEx: Femtosecond lenticule extraction; df: Degrees of freedom; Chi2: Chi-square test; I2: Extent of inconsistency; Z: Overall effect.

Figure 5. Forest plot of proportion of eyes with CDVA lost two or more lines after SMILE vs FLEx

CDVA: Corrected distance visual acuity; SMILE: Small incision lenticule extraction; FLEx: Femtosecond lenticule extraction; Z: Overall effect.

Figure 6. Forest plot of SE after SMILE vs FLEx

SE: Spherical equivalent refraction; SMILE: Small incision lenticule extraction; FLEx: Femtosecond lenticule extraction; df: Degrees of freedom; Chi2: Chi-square test; I2: Extent of inconsistency; Z: Overall effect.

Figure 7. Forest plot of proportion of eyes SE within±0.50 D after SMILE vs FLEx

SE: Spherical equivalent refraction; SMILE: Small incision lenticule extraction; FLEx: Femtosecond lenticule extraction; df: Degrees of freedom; Chi2: Chi-square test; I2: extent of inconsistency; Z: Overall effect.

Figure 8. Forest plot of total HOAs derived from the anterior corneal surface after SMILE vs FLEx

HOAs: Higher-order aberrations; SMILE: Small incision lenticule extraction; FLEx: Femtosecond lenticule extraction; df: Degrees of freedom; Chi2: Chi-square test; I2: Extent of inconsistency; Z: Overall effect.

Figure 9. Center corneal biomechanical [CCT (A), CH (B), CRF (C)] after SMILE vs FLEx

CCT: Central corneal thickness; CH: Corneal hysteresis; CRF: Corneal resistance factor; SMILE: Small incision lenticule extraction; FLEx: Femtosecond lenticule extraction; df: Degrees of freedom; Chi2: Chi-square test; I2: extent of inconsistency; Z: Overall effect.