ABSTRACT
As a relatively new procedure,small incision lenticule extraction (SMILE) is still in its initial stage.Despite the fact that it has shown safety,efficacy,predictability,and stability,the clinical outcomes were diversiform among individuals.How to improve visual quality by designing individualized parameters is one of the researching focuses in corneal refractive surgery.This article reviewed the operative design,such as pluse energy,scanning patterns,cap,incision,optical zone and its influences on surgical results.
ABSTRACT
Objective To investigate the correlations between corneal biomechanical properties and corneal high-order aberrations (HOAs) in myopic eyes.Methods In this retrospective study,263 right eyes with myopia or myopic astigmatism were enrolled from January to October 2015 in Tianjin Eye Hospital.The values of first applanation time (A1T),first applanation length (A1L),first applanation velocity (A1V),second applanation time (A2T),second applanation length (A2L),second applanation velocity (A2V),highest concavity time (HCT),highest concavity deformation amplitude (HCDA),highest concavity peak distance (HCPD),highest concavity radius (HCR) and non-contact intraocular pressure (IOPnct) were measured using the corneal visualization Scheimpflug technology (Corvis ST).The central corneal thickness (CCT) and wavefront aberrations of the anterior,posterior surface,and the total cornea were measured with Pentacam.Pearson correlation and stepwise multivariate linear regression analysis were applied to analyze the correlations between biomechanical properties and corneal HOAs.This study follows the Helsinki declaration.The experiment was approved by the Ethic Committee of Tianjin Eye Hospital.Informed consent was signed from each patient.Results There was a correlation between biomechanical properties and corneal HOAs.Negative correlations were found between A1L and the spherical aberration,HOAs RMS of anterior surface,total RMS and HOAs RMS of the posterior surface and HOAs RMS of the total cornea (P＜0.05).HCRs were negatively correlated with total RMS of the total cornea and the anterior surface (P＜0.05).The A2V was correlated with various aberrations.Multiple stepwise linear regression model analysis showed that,the correlation between the aberrations of anterior surface and biomechanical parameters,and the correlations between the total corneal aberration and biomechanical parameters were weak,the correlations between the aberrations of posterior surface and biomechanical parameters were strong.Conclusions There is a correlation between the biomechanical properties and corneal HOAs.The changes of the corneal biomechanical properties are mainly associated with the posterior corneal aberrations,which may contribute to the early diagnosis of subclinical keratoconus or dilated corneal disease.
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Background The relationship between corneal central thickness (CCT) and corneal biomechanical property does not reflect the effective amount of ablated tissue because CCT measures only the change in a single point.Corneal volume (CV) is a representative parameter of corneal morphology,and it can fully reflect corneal thickness and tissue distribution.Objective This study was to investigate the correlation between volumetric corneal changes and corneal biomechanical properties after small incision lenticule extraction (SMILE).Methods A prospective series cases-observational study was carried out.This study protocol was approved by Ethic Committee of Tianjin Eye Hospital,and written informed consent was obtained from each patient prior to entering the cohort.Sixty-seven right eyes of 67 myopia or myopic astigmatism patients who received SMILE in Tianjin Eye Hospital from June 2014 to July 2015 were included in this study.Before and 3 months after surgery,the CV at 3,3-5,5-7 and 7-10 mm (CV3,CV3-5,CV5-7,CV7-10) was measured by Pentacam anterior segment analysis system,and corneal hysteresis (CH) and corneal resistance factor (CRF) were obtained by ocular response analyzer (ORA).The changes of CV (ACV),CH (ACH) and CRF (ACRF) were calculated,and the correlations between ACV and ACH or ACRF were analyzed.Results CV3,CV3-5 and CV5-7 values after SMILE were significantly lower than those before SMILE (t =36.24,20.38,16.17,all at P＜ 0.001).The CH values before and after SMILE were (10.06± 1.11) mmHg and (8.10± 1.05) mmHg (1 mmHg =0.133 kPa),and the CRF values before and after SMILE were (10.40 ± 1.38) mmHg and (6.91 ± 1.19) mmHg,respectively,showing significant reduces after SMILE than before SMILE (t =16.71,27.41,both at P＜0.001).Positive correlations were seen between the CV values at different corneal areas and CH value or CRF value.Moderate positive correlations were found between CV3 and CH or CRF (r =0.571,0.569;both at P＜0.001) before surgery,and 3 months after surgery,a weak positive correlation was seen between ACV3 and ACH (r =0.394,P ＜ 0.001) or a moderate positive correlation between ACV3 and ACRF (r=0.501,P＜0.001).Conclusions The CV value is gradually increased from the central cornea to periphery cornea.The CV change is associated with CH and CRF changes after SMILE,and CV3 probably is a useful parameter for the evaluation of corneal biomechanics after refractive surgery.
ABSTRACT
Background Small incision lenticule extraction (SMILE) is increasingly applied in the correction of myopia and astigmatism.However,the early clinical outcomes of SMILE for different refractive myopia and astigmatism is seldom reported.Objective This study was to investigate the safety,efficacy,predictability and early stability after SMILE in low,moderate and high myopia.Methods A series of cases-observational study was carried out.A total of 195 eyes of 108 myopic patients were enrolled in Tianjin Eye Hospital from May to December 2012 under the informed consent.The patients were divided into the low (≤-3.00 D),moderate (＞-3.00 to-6.00 D) and high myopia (＞-6.00 D) groups according to different diopters,with 57 eyes,76 eyes and 62 eyes,respectively.SMILE was performed on all the eyes.The uncorrected visual acuity (UCVA)(LogMAR),best corrected visual acuity (BCVA) (LogMAR),equivalent sphere (SE),intraocular pressure,anterior segment and corneal topography were examined before operation and 1 day,1 week,1 month and 3 months after operation to evaluate the effective index (postoperative UCVA/preoperative BCVA),safety index (postoperative BCVA/preoperative BCVA),predictability and early stability of SMILE.The linear regression analysis was used to analyze the relationships between the attempted refraction and the achieved refraction postoperative 3 months in three groups.Results The percentage of UCVA (LogMAR)＜0.1 was 100％,97.1％ and 92.8％ in the low,moderate and high myopia group,respectively in 3 months after SMILE.The postoperative BCVA of all the operated eyes reached preoperative one.The residual SE was (-0.07±0.16),(-0.05 ±0.20) and (-0.08±0.27)D in the low,moderate and high myopia group,respectively in 3 months after SMILE.The percentage of residual SE±0.5 D was 100％,98.7％ and 93.6％ in the low,moderate and high group,and that of SE±1.0 D was 100％ in all of the groups.The postoperative corrected SE was gradually increased with the raise of predicted SE in the low,moderate and high myopia groups (r=0.942,0.959,0.957,all at P＜0.001).Conclusions SMILE is safe,effective,predictable and stable for the correction of low,moderate and high myopia.The corneal wound healing was slightly slower in the low myopia group than that in the moderate and high group.A slight regression of myopic power appears in high myopia eyes 3 months after SMILE.