经上皮准分子激光角膜切削术治疗近视散光术后散光的矢量分析

目的：采用Alpins矢量分析法分析经上皮准分子激光角膜切削术 （TransPRK）治疗近视散光的效果，探讨影响散光矫正的因素。方法：回顾性系列病例研究。收集2014年1月至2016年6月在汕头国际眼科中心行TransPRK矫正近视散光且术后坚持随访3个月的患者99例（167眼），分成低散光组（-0.25～-0.75 D）和相对高散光组（-1.00～-4.75 D）。采用Alpins矢量分析法对手术前后散光的相关指标进行计算和评估，手术前后指标采用配对t检验；影响散光矫正的因素之间的相关性采用Pearson相关分析。结果：术前主觉验光球镜度为（-3.57±1.22）D，散光度为（-0.93±0.62）D。术后3个月主觉验光球镜度为（+0.12±0.25）D，散光度为（-0.04±0.23）D。目标矫正散光量绝对值（|TIA|）为（0.86±0.58）D，手术矫正散光量绝对值（|SIA|）为（0.87±0.59）D，误差量绝对值（|DV|）为（0.10±0.21）D，误差值（ME） （0.01±0.17）D，误差角（AE） （1.49±13.27）°，矫正指数（CI）为0.98±0.33。|SIA|与|TIA|呈正相关（r=0.94，P < 0.001）。|AE|与|DV|呈正相关（r=0.83，P < 0.001）。ME与|SIA|呈正相关（r=0.23，P < 0.001）。2组|DV|、ME和 CI相似；低度散光组的|AE|为5.78°±16.34°，相对高散光组为1.82°±4.41°，差异有统计学意义（t=2.02，P=0.04）。术后37只患眼（22.0%）有残余散光，其中60%的患者手术前后轴向改变量大于30°，发现术前散光轴变化呈逆时针改变，转轴度为-2.30°±45.88°。结论：TransPRK对散光的矫正效果与散光大小和轴向矫正的准确性关系密切，为了减少术后散光，需提高术中矫正散光大小和轴向的准确性。

Vector Analysis of Astigmatism after Transepithelial Photorefractive Keratectomy for Myopic Astigmatism

Objective: To investigate outcomes of myopic astigmatism correction after transepithelial photorefractive keratectomy (TransPRK) for myopic astigmatism using the Alpins method, and to explore factors affecting the correction of astigmatism. Methods: In this retrospective study, 99 patients (167 eyes with myopic astigmatism) during January 2014 to June 2016 in Joint Shantou International Eye Center were chosen and then divided into a low astigmatism group (-0.25-   -0.75 D) and a high astigmatism group (-1.00-   -4.75 D).Astigmatism status was evaluated based on astigmatism before treatment and 3 months after treatment based on Alpins vector analysis. Pre-op and post-op indexes were compared with a paired t-test, and the correlation of factors affecting the correction of astigmatism was analyzed by Pearson correlation.results: Before surgery, spherical power was -3.57 ± 1.22 D and astigmatism was -0.93 ± 0.62 D based on subjective refraction; and 3 months after surgery spherical power was +0.12 ± 0.25 D and astigmatism was -0.04 ± 0.23 D. Target-induced astigmatism (|TIA|) was 0.86 ± 0.58 D, surgery-induced astigmatism (|SIA|) was 0.87 ± 0.59 D, the difference vector (|DV|) was 0.10 ± 0.21 D, the magnitude of error (ME) was 0.01 ± 0.17 D, the angle of error (AE) was 1.49° ± 13.27° and the correction index (CI) was 0.98 ± 0.33.|SIA| and |TIA| were positively correlated (r=0.94, P < 0.001), |AE| and |DV| were positively correlated (r=0.83, P < 0.001) and ME and |SIA| were positively correlated (r=0.23, P < 0.001). The two groups had a similar |DV|, ME and CI. The low astigmatism group's |AE| was 5.78° ± 16.34°, and the high astigmatism group's |AE| was 1.82° ± 4.41° (t=2.02, P=0.04). After TransPRK, 37 eyes (22.0%) had astigmatism, and 60% of eyes had an axis change of more than 30°. We found that the preoperative cylinder axis moved counter-clockwise to the postoperative cylinder axis, which changed -2.30° ± 45.88°. conclusions:Postoperative astigmatism using TransPRK has a close relationship with the accuracy of astigmatism andaxis correction. In order to reduce postoperative astigmatism, it is necessary to improve the accuracy of the astigmatism and axial direction during the procedure.