实时A型超声角膜测厚指导下的LASIK手术

A-ultrasonic pachymetry-guided LASIK

目的探讨准分子激光原位角膜磨镶术(LASIK)术中再次A型超声角膜测厚对部分患者的临床指导意义。方法对52例(102眼)因角膜中央厚度偏薄和/或屈光度数偏大而被排除在常规LASIK适应证范围以外的近视眼患者,在术中切割角膜瓣前后再行A型超声角膜测量,据测量数据实时监测指导手术。结果102眼间接计算的角膜瓣厚度为(107.76±23.17)μm,有95眼术中测量的角膜中央厚度比术前偏高,其余7眼偏低(t=16.58,P<0.01)。根据再次测量结果计算均符合术前设计所要求的水平而施行LASIK手术。术后1d、10d、1个月、3个月UCVA分别为4.86±0.17、4.95±0.16、4.97±0.15、4.96±0.17。结论LASIK术中制作的角膜瓣厚度因诸多因素的影响与角膜刀头所设定的厚度比较有较大的误差,术前、术中测量的角膜中央厚度也有一定的差异。对于按常规检查计算结果被排除在LASIK手术适应证以外的患者,绝大部分可以通过此方法得到治疗,该方法的疗效与常规LASIK手术无明显差异,并扩大了LASIK手术的适应证。

Objective To evaluate the significance of the application of secondary A-ultrasonic pachymetry during laser in situ keratomileusis （LASIK） for the patients with thinne corneal stroma or suffering from higher myopia. Methods A-ultrasonic pachymetry were performed before and after making of the corneal flap during the LASIK on 102 eyes of 52 cases. LASIK strategy was determined based on the secondary corneal thickness measured by A-ultrasonic pachymetry. The eyes were divided into three groups according to the diopter： Group Ⅰ had 19 eyes with the diopter between -2.75 and -6.00 D, Group Ⅱ had 31 eyes with the diopter between -6.25 and -9.00 D and Group Ⅲ included 31 eyes between -9.25 and -21.75 D. Results The theoretical value of mean central corneal flap thickness in different diopter groups was （107.76±23.17） μm, （110.90±25.51） μm and （107.67±24.07） μm prior to operation without statistically difference （P 〉 0.05）, and the measure value of corneal thickness was （509.46±24.72） μm before operation and （531.00±27.94） μm during the operation （P 〈 0.001） in normal eyes and 509.46±24.72 before operation and 531.00±27.94 during the operation （P 〈 0.001）. The thickness of the stroma bed in all eyes met the demand of a full refractive correction to myopia. The average pre-operation uncorrected visual acuity （UCVA） was 3.75±0. 32, and 4.95±0.16, 4.97±0.15 and 4.96±0.17 at day 1, month 1 and month 3 after operation,respectively. Conclusion Corneal flap thickness in operation is different from corneal blade thickness, and there exist some differences in the central corneal thickness between before and the time performed LASIK surgery. For some myopic eyes with very thin cornea or higher refraction, the intraoperative measurements of corneal thickness can be safer for a full refractive correction.