Underestimation of intraocular lens power for cataract surgery after myopic photorefractive keratectomy
Underestimation of intraocular lens power for cataract surgery after myopic photorefractive keratectomy
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DOI：
10.1016/s0161-6420(99)90153-7
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发表时间：
1999-04-01
期刊：
影响因子：
13.7
通讯作者：
Küchle, M
中科院分区：
文献类型：
--
作者：
Seitz, B;Langenbucher, A;Küchle, M
目的：评估角膜屈光力测量和标准眼内透镜屈光力（IOLP）计算的有效性后photorefractive keratectomy（PRK）. Design：Nonrandomized，前瞻性，横断面，临床研究。32.3+/-6.6年（范围：24.4 - 49.5岁）。在近视矫正前和矫正后15.8 ± 10.4个月进行主观验光、标准角膜曲率、TMS-1角膜地形图分析和角膜厚度测量（n = 24，-1.5至-8.0屈光度[D]，平均-5.4 +/-1.9 D）或近视散光（n = 7，球镜-2.0至-7.5 D，平均-4.4 +/-1.9 D;柱镜-1.0至-3.0 D，平均-1.9 +/-0.7 D）。IOLP计算使用两个不同的公式进行（SRK/T和HAIGIS）。主要结果指标：测量的角膜曲率（K）和地形图模拟角膜曲率（TOPO）（K-meas，TOPOmeas），并根据角膜前表面屈光度的变化或根据角膜屈光不正后等效球镜的变化计算在一个模型中评估角膜屈光度（K-calc，TOPOcalc）、正视眼的IOLP和计算角膜屈光度的术后屈光不正。经腹后，平均K-meas和TOPOmeas显著大于平均KRcalc和TOPOcalc（P <0.0001）（0.4 - 1.4 D，最大3.3 D）。根据计算方法，平均而言，角膜切除术后角膜的相对平坦度被低估了14%至30%（最大为83%）。根据角膜屈光度的计算方法和使用的IOLP计算公式，角膜屈光度后的平均理论IOLP范围为+17.4 D（SRK/T，TOPOmeas）至+20.9 D（HAIGIS，K-calc）。对于两种配方，使用角膜曲率读数的IOLP值显著高于（> 1 D）使用地形图读数的IOLP值（P <0.0001）。白内障手术后理论上引起的平均屈光不正范围为+0.4至+1.4（最大，+3.1）D。角膜屈光力高估和IOLP低估与屈光不正后等效球镜变化（P = 0.001）和屈光不正期间预期的切削深度（P = 0.004）显著相关。结论：为了避免屈光不正后白内障手术后IOLP和远视的低估，必须校正测量的角膜屈光力值。角膜平面等效球镜屈光变化的计算方法似乎是最合适的方法。与该方法相比，直接屈光度测量平均低估了角膜屈光不正后24%的角膜扁平度。使用传统的地形分析似乎会增加出错的风险。然而，由于这项研究是回顾性的和理论性的，仍然需要一个大的前瞻性调查，以验证作者的发现。
Objective: To assess the validity of corneal power measurement and standard intraocular lens power (IOLP) calculation after photorefractive keratectomy (PRK).Design: Nonrandomized, prospective, cross-sectional, clinical study.Participants: A total of 31 eyes of 21 females and 10 males with a mean age at the time of surgery of. 32.3 +/- 6.6 years (range, 24.4-49.5 years).Intervention: Subjective refractometry, standard keratometry, TMS-1 corneal topography analysis, and pachymetry were performed before and 15.8 +/- 10.4 months after PRK for myopia (n = 24, -1.5 to -8.0 diopters [D], mean -5.4 +/- 1.9 D) or myopic astigmatism (n = 7, sphere -2.0 to -7.5 D, mean -4.4 +/- 1.9 D; cylinder -1.0 to -3.0 D, mean -1.9 +/- 0.7 D). The IOLP calculations were done using two different formulas (SRK/T and HAIGIS).Main Outcome Measures: Keratometric power (K) and topographic simulated keratometric power (TOPO) as measured (K-meas, TOPOmeas) and as calculated according to the change of power of the anterior corneal surface or according to the spherical equivalent change after PRK (K-calc, TOPOcalc), IOLP for emmetropia, and postoperative ametropia for calculated corneal powers were assessed in a model.Results: After PRK, mean K-meas and TOPOmeas were significantly greater (0.4-1.4 D, maximum 3.3 D) than mean KRcalc and TOPOcalc (P < 0.0001). On average, the relative flattening of the cornea after PRK was underestimated by 14% to 30% (maximum, 83%) depending on the method of calculation. The mean theoretical IOLP after PRK ranged from + 17.4 D (SRK/T, TOPOmeas) to +20.9 D (HAIGIS, K-calc) depending on the calculation method for corneal power and IOLP calculation formula used. For both formulas, IOLP values using keratometric readings were significantly higher (>1 D) than IOLP values using topographic readings (P < 0.0001). The theoretically induced mean refractive error after cataract surgery ranged from +0.4 to +1.4 (maximum, +3.1) D. Corneal power overestimation and IOLP underestimation correlated significantly with the spherical equivalent change after PRK (P = 0.001) and the intended ablation depth during PRK (P = 0.004).Conclusions: To avoid underestimation of IOLP and hyperopia after cataract surgery following PRK, measured corneal power values must be corrected. The calculation method using spherical equivalent change of refraction at the corneal plane seems to be the most appropriate method. In comparison with this method, direct power measurements underestimate corneal flattening after PRK by 24% on average. Use of conventional topography analysis seems to increase the risk of error. However, because this study is retrospective and theoretical, there is still a need for a large prospective investigation to validate the authors' findings.