Kapadia M S, Krishna R, Shah S, Wilson S E
Eye Institute, The Cleveland Clinic Foundation, Ohio, USA.
Cornea. 2000 Mar;19(2):174-9. doi: 10.1097/00003226-200003000-00010.
To evaluate retrospectively the effect of spherical excimer laser photorefractive keratectomy (PRK) on astigmatism.
Four hundred seventy consecutive eyes of patients who had PRK for the treatment of myopia without astigmatic keratotomy, PRK reoperation, or other surgical procedures were evaluated in a retrospective clinical study. PRK was performed using the Summit Apex excimer laser with attempted corrections from 1 to 7 diopters (D) of myopia. Preoperative and postoperative astigmatism was determined by manifest refraction refined with a 0.25-D Jackson cross cylinder and evaluated with vector analysis.
Eighty-five ( 18%) eyes continued to have a spherical refraction after PRK, 53 (11%) eyes had the same preoperative astigmatism, and 332 (71%) eyes had a change in magnitude of astigmatism > or =0.25 D after spherical PRK. The absolute change in astigmatism magnitude irrespective of axis was +0.4 +/- 0.4 (standard deviation) D at 6 months after PRK. Eyes with change in astigmatism power tended to have higher preoperative myopia and higher preoperative astigmatism. Vector analysis revealed surgically induced astigmatism was 0.68 +/- 0.50 D (range, 0-3.25 D) at 1 month and 0.56 +/- 0.47 D (range, 0-3.1 D) at 12 months after spherical PRK.
Spherical excimer laser PRK is associated with significant surgically induced astigmatism that is likely related to decentration of the ablation, excimer laser beam irregularities, and variations in wound healing across the ablated zone. Surgically induced astigmatism will complicate attempts to correct astigmatism simultaneously at the time of PRK and suggest that such attempts are likely to be problematic for lower levels of astigmatism.
回顾性评估准分子激光原位角膜磨镶术（PRK）治疗散光的效果。
在一项回顾性临床研究中，对470例连续接受PRK治疗近视且未行散光性角膜切开术、PRK再次手术或其他手术的患者的眼睛进行评估。使用Summit Apex准分子激光进行PRK，尝试矫正1至7屈光度（D）的近视。术前和术后散光通过使用0.25 D杰克逊交叉柱镜进行的显验光确定，并通过矢量分析进行评估。
85只（18%）眼睛在PRK后仍为球镜度屈光不正，53只（11%）眼睛术前散光相同，332只（71%）眼睛在球镜PRK后散光度数变化≥0.25 D。PRK后6个月，散光度数的绝对变化（不考虑轴位）为+0.4±0.4（标准差）D。散光度数有变化的眼睛术前近视度数和术前散光度数往往较高。矢量分析显示，球镜PRK后1个月手术诱导散光为0.68±0.50 D（范围0 - 3.25 D），12个月时为0.56±0.47 D（范围0 - 3.1 D）。
球镜准分子激光PRK与显著的手术诱导散光相关，这可能与消融中心偏移、准分子激光束不规则以及消融区伤口愈合差异有关。手术诱导散光会使在PRK时同时矫正散光的尝试变得复杂，并表明对于较低程度的散光，这种尝试可能会有问题。
