近视眼飞秒激光小切口角膜透镜取出术前后角膜体积变化与角膜生物力学改变的关联性

摘要

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.%背景 单纯研究中央角膜厚度(CCT)与角膜生物学特性的关系无法全面阐明角膜结构变化对角膜生物力学的影响.角膜体积(Cv)是角膜形态结构的主要特征性参数之一,能更全面地反映角膜整体的厚度及组织分布情况,但目前相关研究鲜见报道.目的 分析飞秒激光小切口角膜透镜取出术(SMILE)术后CV变化与角膜生物力学改变的关系.方法 采用前瞻性系列病例观察研究方法,纳入2014年6月至2015年7月于天津市眼科医院行SMILE手术的近视及近视散光患者67例67眼,均选取右眼的测定结果进行分析.术前及术后3个月分别采用Pentacam眼前节分析系统测量术眼角膜3、3～5、5～7和7～ 10 mm环形区的角膜体积(Cv3、CV3-5、CV5-7、CV7-10);采用眼反应分析仪(ORA)系统测量术眼角膜生物力学指标,包括角膜滞后量(CH)及角膜阻力因子(CRF),计算手术前后CV.CH值和CRF值变化量(△);对术眼术前CV与CRF值和CH值之间的关系进行评估,并对△CV与△CH和△CRF之间的关联性进行评价. 结果 SMILE术后3个月术眼CV3、CV3-5和CV5-7值较术前均明显下降,差异均有统计学意义(t=36.24、20.38.16.17,均P＜0.001);术前及术后3个月术眼的CH值分别为(10.06±1.11)mmHg和(8.10±1.05)mmHg(1 mmHg=0.133 kPa),CRF分别为(10.40±1.38) mmHg和(6.91±1.19) mmHg,术眼术后CH值和CRF值均较术前下降,差异均有统计学意义(t=16.71、27.41,均P＜0.001).术前术眼角膜不同区域CV值与CH值和CRF值均呈正相关,其中CV3与CH值和CRF值均呈中等正相关(r=0.571、0.569,均P＜0.001),术后3个月△CV3与△CH呈弱正相关(r=0.394,P＜0.001),与△CRF呈中等正相关(r=0.501,P＜0.001).结论 CV从中央区到周边区逐渐增加.术后CV与CH和CRF均呈正相关,CV3可能是角膜屈光术后角膜生物力学特性改变的评估参数之一.