Zheng L, Merriam J C, Zaider M
Edward S. Harkness Eye Institute, College of Physicians and Surgeons, Columbia University, New York, USA.
Trans Am Ophthalmol Soc. 1997;95:387-410; discussion 410-5.
This study compares the change over time of the astigmatism caused by "large" incision extracapsular cataract extraction (ECCE) and three smaller incisions for phakoemulsification. Based on this data, a mathematical model that predicts the course of astigmatism after a superior incision of length 3 to 12 mm has been developed. The relationship of axial length and preoperative astigmatism to induced post-operative astigmatism, the recovery of visual acuity, and the rate of YAG laser capsulotomy after each procedure also are documented.
Induced astigmatic change was calculated using a simple method of vector analysis. The change in induced astigmatism was calculated for 8 years after ECCE (n = 144), for 3 years after 6 mm superior incisions (6SUP) (n = 93), for 2 years after 3 mm superior incisions (3SUP) (n = 120), and for 18 months after 3 mm temporal incisions (3Temp) (n = 65). Plotted semi-logarithmically, the astigmatic change in each group may be represented mathematically.
Two weeks after ECCE the mean induced cylinder was +3.47 D, which decayed to about -1.25 D after 6 months. Induced cylinder increased gradually to about -1.6 D after 8 years, although this further change was not significantly different than that at 6 months after surgery. For the phako groups, the net induced cylinder on the first post-operative day was: +1.23 D (6SUP), +0.49 D (3Sup), and -0.19 D (3Temp). After 6Sup the wound was astigmatically stable after approximately 3 months, and 3 years after surgery net induced cylinder was -0.66 D. After 3Sup the wound was astigmatically stable after about 6 weeks, and after 18 months net induced cylinder was -0.35 D. No significant change in astigmatism was detected at any time after 3Temp. Maximum visual acuity was reached after a mean of approximately 6 weeks after ECCE, 2 weeks after 6Sup, and between 1 day and 1 week after 3Sup and 3Temp. The rate of YAG laser capsulotomy was higher after ECCE than after any of the phakoemulsification procedures. No relationship of axial length or preoperative astigmatism to astigmatic change was detected.
Incision size and location affect post-operative astigmatism. Induced astigmatism decreases with wound size, and only the 3 mm temporal incision is astigmatically neutral. The time for visual recovery increases with wound size. There appears to be less need for laser capsulotomy after phakoemulsification with capsulorrhexis than after ECCE. Axial length does not affect induced astigmatism after any of the 4 incisions, and preoperative astigmatism does not affect astigmatic change after ECCE and 6Sup.
本研究比较了“大”切口白内障囊外摘除术（ECCE）及三种较小切口的超声乳化白内障吸除术随时间推移引起的散光变化。基于这些数据，已建立了一个数学模型，用于预测长度为3至12毫米的上方切口术后散光的发展过程。同时还记录了眼轴长度和术前散光与术后诱导散光、视力恢复以及每种手术术后YAG激光后囊切开术发生率之间的关系。
采用简单的矢量分析方法计算诱导散光变化。计算了ECCE术后8年（n = 144）、6毫米上方切口（6SUP）术后3年（n = 93）、3毫米上方切口（3SUP）术后2年（n = 120）以及3毫米颞侧切口（3Temp）术后18个月（n = 65）的诱导散光变化。以半对数形式绘制图表后，每组的散光变化可用数学方法表示。
ECCE术后两周平均诱导柱镜为 +3.47 D，6个月后降至约 -1.25 D。8年后诱导柱镜逐渐增加至约 -1.6 D，尽管这一进一步变化与术后6个月时并无显著差异。对于超声乳化组，术后第一天的净诱导柱镜分别为：+1.23 D（6SUP）、+0.49 D（3Sup）和 -0.19 D（3Temp）。6SUP术后约3个月伤口散光稳定，术后3年净诱导柱镜为 -0.66 D。3SUP术后约6周伤口散光稳定，18个月后净诱导柱镜为 -0.35 D。3Temp术后任何时间均未检测到散光有显著变化。ECCE术后平均约6周、6SUP术后2周、3SUP和3Temp术后1天至1周达到最大视力。ECCE术后YAG激光后囊切开术的发生率高于任何一种超声乳化手术。未检测到眼轴长度或术前散光与散光变化之间的关系。
切口大小和位置会影响术后散光。诱导散光随伤口大小减小，只有3毫米颞侧切口无散光变化。视力恢复时间随伤口大小增加。与ECCE相比，连续环形撕囊超声乳化术后似乎对激光后囊切开术的需求更少。眼轴长度对4种切口中任何一种术后诱导散光均无影响，术前散光对ECCE和6SUP术后的散光变化也无影响。
