目的：使用UBM在术前测量巩膜前表面到硅油泡的距离，利用三角函数的计算公式，从而计算出23G套管的安全活动角度，最大限度避免术中取油时损伤视网膜。

方法：从2017/03-2017/09，共选取15例硅油眼患者，年龄32～69岁，首次手术均为视网膜脱离，左眼10例，右眼5例，均采用23G套管通过23G灌注管连接5 mL注射器，直接取油的方法。术前均通过UBM测量角膜缘后4 mm，2：00和10：00位的巩膜壁前表面到硅油泡的距离，定义为 “A”； 23G套管的长度为4 mm，定义为 “C”； 将巩膜套管最大活动角度时的巩膜内壁的宽度定义为 “B”； “A”，“B”，“C”构成直角三角形。利用三角函数计算出最大活动角度时“A”和“C”的正弦值，参考三角函数表得出23G套管的安全活动角度。根据此角度指导术中硅油取出时23G套管的活动范围，同时观察取油时间和穿刺口视网膜情况。

结果：所有患者均顺利取出硅油，所用时间平均为4.78±0.13min。穿刺管口处视网膜未见任何新发视网膜裂孔和其他损伤。2：00位巩膜壁前表面到硅油泡的距离为0.82～2.81(1.62±0.41)mm，10：00位为0.98～2.19(1.71±0.34)mm，2：00位巩膜套管的安全活动角度(指套管和巩膜壁的角度)不能低于11～44(24.14±6.95)°，10：00巩膜套管的安全活动角度不能低于14～33(25.45±5.41)°。模拟图形构建，计算穿刺套管安全活动角度为不低于52°。

结论：利用三角函数的方法，结合UBM测量数据，计算套管安全活动角度可以有效的指导23G硅油取出术中套管针的活动范围，本研究建议套管移动角度不要低于50°，可以最大限度的避免医源性裂孔的发生。

METHODS: From March 2017 to September 2017, 15 patients with SO filled eyes were enrolled in this retrospective analysis. Based on ultrasound biomicroscopy(UBM), the distance from the front surface of the sclera at the 2 o'clock and the 10 o'clock positions to the SO bubble at 4 mm behind the corneal limbus was measured and defined as “A”. The length of the 23G cannula(4 mm)was defined as “C”. The width of the scleral inner wall at the maximum operating angle of the scleral trocar was defined as “B”. The safe movement angle of the 23G cannula was determined according to the trigonometric function table. Using the self-made SO removal device connected to the 23G puncture cannula, the SO was successfully removed from all patients.

RESULTS: The average SO removal time for all patients was 4.78±0.13min. The trigonometric function was used to work out the distance from the scleral front surface to the SO bubble, which was 0.82-2.81(1.62±0.41)mm at the 2 o'clock position, and 0.98-2.19(1.71±0.34)mm at the 10 o'clock position. Finally, the verification analysis using geometric model calculation showed that the optimal movement angle of the cannula was 52°.

CONCLUSION:Combining the trigonometric function and UBM measurement to calculate the safe movement angle of a 23G cannula can effectively guide the moving range of the trocar during SO removal. A movement angle of the cannula larger than 50° may avoid the occurrence of a retinal tear.