ABSTRACT
As a relatively new procedure, femtosecond laser small incision lenticule extraction (SMIIE) is still in its initial stage.Despite the safety, efficacy, predictability and stability it has showed in refractive error correction, there are still reports of intraoperative complications resulting in different clinical outcomes in SMILE.SMILE includes the production of lenticule by femtosecond laser, the separation and extraction of lenticule, and intraoperative complications may occur in every step.The production of the lenticule is completely dependent on the femtosecond laser, so complications related to femtosecond lasers are inevitable, such as suction loss, opaque bubble layer and black spots.Separation and extraction of the lenticule relies on the experience and surgical skills of surgeon, during which, torn corneal cap, difficult lenticule extraction, lenticule remnants, bleeding and lenticule decentration may occur.In this article, the categories, reasons, management and effects of intraoperative complications on outcome in SMILE were summarized to improve the ability of ophthalmologists to handle intraoperative incidents and enhance surgical safety.
ABSTRACT
Background Recently,small incision lenticule extraction (SMILE) procedure is used to correct myopia.The clinical safety and efficiency of SMILE have been approved,but its predictability to corneal ablation depth is brought into focus.Objective This study was to compare the predictability of ablation depth in central cornea between SMILE and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for myopia.Methods A nonrandomized controlled clinical study was performed.Two hundred and seventy eyes of 135 myopic patients who were going to receive corneal refractive surgery were included in Beijing Tongren Hospital from October 2015 to May 2016.SMILE and FS-LASIK were performed on 138 eyes of 69 patients and 132 eyes of 66 patients matched in demography respectively under the informed consent.Central corneal thickness was measured by RTVue FD-OCT before and 1 week after surgery.The refractive power,actual ablation depth (difference of central corneal thickness before and after surgery) and central corneal cutting error (difference between theoretically expected ablation depth and real ablation depth) were intergrouply compared,and the correlation of real ablation depth with theoretically expected ablation depth was assessed.Results No significant difference was found in spherical power,astigmatic power and spherical equivalent after surgery between SMILE group and FS-LASIK group (t =-1.826,-1.405,-1.420,all at P＞0.05).The actual ablation depth was (76.96± 15.27)μm in the SMILE group,which was significant lower than (96.76± 16.52) μm of theoretically expected ablation depth (t =-23.016,P ＜ 0.01);however,there was no significant difference in the FS-LASIK group between actual and expected ablation depth ([77.92 ± 18.69] μm versus [77.42± 15.60] μm) (t =-0.604,P =0.547).The central corneal cutting error was (20.55 ± 8.51) μm in the SMILE group and (7.17±5.97) μm in the FS-LASIK group,showing a significant difference between them (t=14.950,P＜0.01).The positive linear correlations were seen between actual and expected ablation depth in both SMILE group and FS-LASIK group (r=0.799,0.867,both at P＜0.01).The actual ablation depth was increased over expected ablation depth,with the regression equations of Y=3.892+0.749X in the SMILE group and Y=3.443 + 0.957X in the FS-LASIK group.Conclusions The actual corneal ablation depth is less than expected corneal ablation depth in SMILE procedure,while in FS-LASIK procedure,the actual corneal ablation depth appears to be consistent with the expected one,inferring a good predictability in corneal ablation depth in FS-LASIK surgery.
ABSTRACT
Background Researches showed that femtosecond laser corneal small incision lenticule extraction (SMILE) was used in the correction of myopia and myopic astigmatism due to its fast recovery,good shortterm efficacy and few complications.However,few research focused on its long-term efficacy.Objective Thisstudy was to evaluate the effectiveness,safety,predictability,stability and complications of SMILE.Methods A serial cases-observational study was carried out under the approval of Ethic Committee of Henan Eye Institute and informed consent of patients.Sixty-seven eyes of 34 patients with myopia and myopic astigmatism were included in Henan Eye Institute from January to June 2013.All the patients received SMILE and followed-up for 2-year duration.The uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA),automatic optometry,intraocular pressure and corneal topography were examined before surgery and 1 day,1 week,1 month,3 months,1 year and 2 years after surgery and calculated the spherical equivalent (SE).The long-term efficacy of SMILE included effective index (preoperative BCVA/postoperative UCVA),safety index (postoperative BCVA/ preoperative BCVA),predictability (linear regression analysis between actual SE and attempted SE) and refractive stability (SE changes at postoperative time points).Results The preoperative BCVA was ≥ 20/20 in 60 eyes with the percentage of 89.55％.UCVA≥ 20/20 were found in 61 eyes and 60 eyes in postoperative 3 months and 2 years respectively (91.04％ and 89.55％).The effective index was 1.038±0.182 and 1.029±0.231 in postoperative 3 months and 2 years respectively,showing an insignificant difference between them (t =0.400,P ＞ 0.05).Compared with the preoperative BCVA,8.96％ (6/67) and 10.45％ (7/67) eyes lost 1 line at 3 months and 2 years after surgery,respectively.The safety indexes were 1.141±0.193 and 1.312±0.242 at 3 months and 2 years after surgery,with no significant difference between them (t =0.414,P＞0.05).A linear correlation was found between actual SE and attempted SE both at postoperative 3 months and 2 years,with the linear regression equations of Y=0.897 1X-0.440 8 (R2 =0.914 2,P＜0.05) and Y =0.893 7X-0.382 3 (R2 =0.915 7,P＜0.05),respectively.The SE was (0.013±0.578),(-0.033±0.489),(-0.106±0.508),(-0.103±0.375),(-0.154±0.518) and (-0.147±0.366)D 1 day,1 week,1 month,3 months,1 year and 2 years after surgery,respectively,and there were no significant difference among different time points (F =0.185,P =0.176).Eighteen in the 67 eyes occurred opaque bubble layer after surgery.Diffuse lamellar keratitis appeared in 6 eyes and punctate keratitis was in 2 eyes.These complications were cured 1 month after administration of drugs.Conclusions SMILE is good in effectiveness,safety,predictability and refreactive stability and has fewer complications during 2-year following-up.
ABSTRACT
Background The visual quality and corneal biomechanical change are two major sides for evaluating the outcomes of cornea refractive surgery.It was determined that small incision lenticule extraction (SMILE) can improve the visual outcomes,but its long-term effects on corneal biomechanical are not known clearly.Objective This study was to investigate the change of corneal biomechanics and influence factors following SMILE.Methods A serial cases-observional study was performed.One hundred eyes of 58 patients with a mean spherical diopter (-5.00 ± 1.55) D and cylindrical diopter (-0.98 ± 0.87) D were included in Tianjin Eye Hospital from August 2011 to July 2013 under the informed consent.Corneal biomechanical parameters,including corneal resistance factor (CRF) and cornea hysteresis (CH) were measured using the ocular response analyzer (ORA) in preoperation and postoperative 1,3,6 and 12 months,respectively.The patients were grouped based on different lenticule thickness ratio (LTR),preoperative CRF values and residual stromal thickness (RST) separately,and the correlations of LTR,preoperative CRF and RST with ΔCRF and ΔCH were assessed.In addition,the associations between ΔCRF or ΔCH and related preoperation parameters were evaluated.Results The CRF and CH values at postoperative 1 month were (7.12 ± 1.20) mmHg and (7.90 ± 0.97) mmHg,which were significantly lower than preoperative (10.17±1.46) mmHg and (10.00±1.16) mmHg,respectively (t=15.552,P=0.000;t =13.411,P=0.000).The CRF values at postoperative 3,6 and 12 months were (7.06±0.90),(6.98 ± 1.11) and (6.87 ± 1.07) mmHg,and those of CH were (8.12 ±0.84),(8.12 ±0.97) and (8.14 ±0.86) mmHg,and no significant differences were found in CRF and CH between the adjacent time points (CRF:P =0.848,0.992,0.270;CH:P =0.370,0.791,0.777).Positive correlations were seen between the ΔCRF or ΔCH and LT/preoperative central corneal thickness (CCT) (LTR),preoperative CRF or preoperative CH values,respectively (LTR:r =0.468,P =0.000;r =0.299,P =0.004;preoperative CRF:r =0.696,P =0.000;r =0.590,P =0.000;preoperative CH:r =0.576,P =0.000;r =0.690,P =0.000).ΔCRF and ΔCH were negatively correlated with preoperative spherical equivalent diopter (r =-0.496,P =0.000;r =-0.292,P =0.010),the sum of preoperative spherical diopter and cylindrical diopter (r =-0.484,P =0.000;r =-0.293,P =0.005) or RST/preoperative CCT (r =-0.362,P =0.000;r =-0.243,P =0.019) and were positively correlated with lenticule (r =0.495,P =0.000;r =0.325,P =0.002).No significant association was found between ΔCRF or ΔCH and age,preoperative CCT and preoperative mean keratometry (all at P＞0.05).Conclusions Corneal biomechanical strength is decreased at the early stage after SMILE.However,biomechanical strength gradually enhances 1 month after surgery and tends to stability.The large RST/preoperative CCT can improve postoperative CRF and CH.The another main factor affecting the corneal biomechanics after SMILE is corrected-diopter.