目的：采用Alpins矢量分析法评估飞秒激光小切口角膜基质透镜取出术(SMILE)术中应用十字定位法矫正低中度散光的临床效果。

方法：前瞻性随机对照研究。纳入2022-05/11在西安市第一医院激光近视治疗中心进行SMILE手术且散光度数≤1.50 D的低中度顺规散光患者50例81眼，依据随机表分为十字组患者25例41眼术中在进行标准SMILE程序之前术者根据十字交叉线调整患者头位，使患者双眼外眦与水平线对齐，眉心及鼻梁与垂直线对齐； 未用十字定位法的对照组25例40眼。观察两组患者术后3 mo视力及屈光情况，采用Alpins矢量分析法对散光变化进行分析评估。

结果：随访期间十字组失访6例11眼，对照组失访8例14眼。最终十字组纳入19例30眼，对照组纳入17例26眼。术后3 mo，两组患者术眼裸眼视力(UCVA)均≥1.0，均未出现严重并发症，两组间UCVA、最佳矫正视力(BCVA)、球镜度及等效球镜度比较均无差异(均P>0.05)。十字组柱镜度数0.00(0.00，0.00)D小于对照组-0.13(-0.50，0.00)D(P=0.01)。矢量分析结果显示，十字组的矢量误差(DV)低于对照组\〖0.00(0.00，0.00)vs 0.13(0.00，0.50)， P=0.01\〗，成功指数(IOS)优于对照组\〖0.00(0.00，0.00)vs 0.18(0.00，0.77)， P<0.01\〗。术后3 mo，十字组和对照组角度误差(AE)在±5°内的眼数分别为26眼(87%)、15眼(58%)。

结论：SMILE术中应用十字定位法校准患者头位，减小了SMILE矫正低中度散光的轴位误差，提高SMILE矫正低中度散光的精确性。

METHODS: A total of 50 patients(81 eyes)with low and moderate astigmatism with the rule ≤1.50 D who underwent SMILE surgery at the laser myopia treatment center of Xi'an No.1 Hospital from May 2022 to November 2022 were included in the prospective randomized controlled study, and they were divided into two groups according to the random table, with 25 case(41 eyes)in cross-positioning group and 25 cases(40 eyes)in control group. In the cross-positioning group, the patients' head position was adjusted based on the cross intersection lines before the standard SMILE procedure, aligning the lateral canthi with the horizontal line and the midpoint of the eyebrows and the nose bridge with the vertical line. Postoperative visual acuity and refractive results at 3 mo were observed in both groups, and astigmatic changes were analyzed and evaluated using the Alpins vector analysis method.

RESULTS: During the follow-up period, 6 cases(11 eyes)in the cross-positioning group were lost to follow-up, while in the control group, 8 cases(14 eyes)were lost to follow-up, with 19 cases(30 eyes)and 17 cases(26 eyes)finally included in the cross-positioning group and the control group, respectively. At 3 mo postoperatively, the uncorrected visual acuity(UCVA)of both groups' operated eyes was ≥1.0, and no serious complications occurred, with no significant differences in UCVA, best corrected visual acuity(BCVA), spherical power, and spherical equivalent between the cross-positioning group and the control group(all P>0.05). The cylindrical power in the cross-positioning group was 0.00(0.00, 0.00)D, which was lower than -0.13(-0.50, 0.00)D in the control group(P=0.01). The vector analysis results showed that the difference vector(DV)in the cross-positioning group was lower than that in the control group \〖0.00(0.00, 0.00)vs 0.13(0.00, 0.50), P=0.01\〗, and the index of success(IOS)was better than that of the control group \〖0.00(0.00, 0.00)vs 0.18(0.00, 0.77), P<0.01\〗. At 3 mo postoperatively, 26(87%)and 15(58%)eyes in the cross-positioning group and control groups achieved an angle of error(AE)within ±5°, respectively.

CONCLUSION: The cross positioning method was used to calibrate the patients' head position during SMILE surgery, which reduced the axial position error and improved the accuracy of SMILE in correcting low and moderate astigmatism.