近视眼飞秒激光小切口基质透镜取出术后角膜光学质量的客观评估

背景 目前评价飞秒激光小切口基质透镜取出术(SMILE)术后角膜光学质量的方法多基于单一的散射、衍射或像差因素,因此不能对角膜光学质量进行全面和客观评价,而调制传递函数(MTF)及斯特列尔比(SR)综合了上述多因素评价方法,是评估术后角膜光学质量方法学的研究方向. 目的 利用角膜MTF及SR客观分析SMILE术后术眼在明视和暗视环境下(分别为3 mm和6 mm瞳孔直径)角膜光学质量的变化.方法 采用系列病例观察研究方法和术眼手术前后自身对照研究设计,纳入2013年12月至2014年3月在天津市眼科医院接受SMILE的患者32例63眼,分别于术前、术后1周、1个月及3个月记录裸眼视力(UCVA)、最佳矫正视力(BCVA)和有效性指数(术后UCVA/术前BCVA);分别于上述时间点对术眼行电脑验光和综合验光仪验光,记录手术前后术眼屈光度变化;采用Sirius眼前节分析系统测定3 mm和6 mm瞳孔直径下不同空间频率(10、20、30、40、50和60 c/d)角膜前表面MTF和SR值,并测定术眼手术前后角膜前表面总高阶像差均方根值(RMS),以评估术眼SMILE手术前后角膜光学质量变化. 结果 术后1周、1个月、3个月UCVA(LogMAR)≥0.8者分别为59、62和63眼,分别占93.65％、98.41％和100％,术眼上述时间点有效性指数分别为1.104±0.128、1.126±0.145和1.158±0.208.术眼术后3个月等效球镜度和柱镜度均在正常范围.术眼术后各时间点3 mm瞳孔直径垂直及水平子午线各空间频率下MTF值较术前均明显增加,6 mm瞳孔直径下垂直子午线10、20、30和40 c/d空间频率MTF值较术前明显增加,差异均有统计学意义(均P＜0.05),而手术前后不同时间点6 mm瞳孔直径下水平子午线各空间频率MTF值总体比较差异均无统计学意义(均P＞0.05).术眼术后各时间点3 mm及6 mm瞳孔直径下的SR与术前相比呈上升趋势,差异均有统计学意义(均P＜0.05);且各时间点3 mm瞳孔直径下SR均大于相应的6 mm瞳孔直径下SR值,差异均有统计学意义(均P＜0.05).术眼手术前后不同时间点3 mm及6 mm瞳孔直径下角膜前表面RMS总体比较差异均无统计学意义(3 mm瞳孔直径:F=1.348,P=0.184;6 mm瞳孔直径:F=1.990,P=0.137). 结论 SMILE手术可有效改善近视及近视散光患者术后角膜光学成像质量,术眼术后明视环境下较暗视环境下角膜光学质量改善更为明显.

Assessment of corneal optical quality following small incision lenticule extraction for myopia

Background The current evaluation of corneal optical quality after small incision lenticule extraction (SMILE) is based on the single factor,such as scattering,diffraction or aberration,and all of them are not comprehensive and objective methods.Modulation transfer function (MTF) and Strehl ratio (ST) are novel parameters of corneal optical quality,which can be used to assess the optical quality comprehensively.Objective This study was to evaluate the change of MTF and SR under the photopic and scotopic environment (3 mm and 6 mm pupil size,respectively) after SMILE procedure.Methods The study protocol was approved by Ethic Committee of Tianjin Eye Hospital,and written informed consent was obtained from each patient before any medical procedure.A series cases-observational study with self-control design was carried out.Sixty-three eyes of 32 myopia or myopic astigmatism patients who underwent SMILE surgery in Tianjin Eye Hospital were included from December 2013 to March 2014.The uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA) (LogMAR),the effective index (postoperative UCVA/preoperative BCVA) and refractive diopter were examined,and the MTF,SR and root mean square (RMS) on the anterior corneal surface were measured under the 3 mm and 6 mm pupil size at different spatial frequencies (10,20,30,40,50 and 60 c/d) by Sirius anterior analyzer before surgery and 1 week,1 month and 3 months after surgery,respectively.Results UCVA was ≥0.8 in 59,62 and 63 eyes in 1 week,1 month and 3 months after SMILE,with the percentage of 93.65％,98.41％ and 100％,and the effective index was 1.104± 0.128,1.126±0.145 and 1.158±0.208,respectively.The refractive diopter was normal in the eyes at postoperative 3 months.The MTFs of various spatial frequencies on the vertical and horizontal meridian under the 3 mm pupil size after SMILE were significantly higher than those before SMILE,while under the 6 mm pupil size,the MTFs were higher only on vertical meridian and 10,20,30 and 40 e/d,and there were not significant differences on the horizontal meridian (all at P＜0.05).The SRs under the 3 mm and 6 mm pupil size showed increasing softly after surgery in comparison with before surgery,and the SRs were higher under the 3 mm pupil size than those under the 6 mm pupil size at various time points (all at P＜0.05).There were not significant differences in RMS among different time points under both 3 mm pupil size and 6 mm pupil size (3 mm pupil size:F =1.348,P =0.184;6 mm pupil size:F=1.990,P=0.137).Conclusions SMILE provides a great improvement in corneal optical quality for myopia or myopic astigmatism patients,which is more distinct in photopic condition than that in scotopic condition.