影响软性散光隐形眼镜适配的角膜地形图定量描述符。

Szczotka Loretta B, Roberts Cynthia, Herderick Edward E, Mahmoud Ashraf

Department of Ophthalmology, Case Western Reserve University & University Hospital of Cleveland, Cleveland, Ohio 44106, USA.

Cornea. 2002 Apr;21(3):249-55. doi: 10.1097/00003226-200204000-00003.

PURPOSE

Empirical soft toric contact lens fitting based on manifest refraction and keratometry often presents unanticipated fitting and power errors upon initial lens dispensing. However, corneal topography may provide features that influence soft toric lens performance, flexure, and back vertex power in situ, which may assist in improved fitting guidelines. In this study, quantitative topographic descriptors were generated and analyzed as potential variables in predicting soft toric fitting success.

METHODS

One hundred five eyes of 54 patients were empirically fit with back surface toric, prism ballasted, soft contact lenses after videokeratography was performed with the EyeSys 2000 (v. 4.0) or Humphrey Atlas (v. A6) instrument. Custom software was written to generate 54 separate quantitative descriptors of shape and astigmatism from the raw data files. A logistic regression was used to determine which variables significantly contributed to a successful or failed fit.

RESULTS

Two types of empirical fitting failures were identified: loose fit (n = 15) and power errors (n = 17). The following variables were associated with a fitting failure: flat simulated keratometry (SimKf2b) within the central 3 mm zone, steep simulated keratometry (SimKs2b) within the central 3 mm zone, a difference between central and peripheral flat meridian axis (DIFFAXIS), and a difference between central and peripheral astigmatism (DIFFASTIG). For fitting failures caused by power errors, a larger steep SimKs2b (p< 0.01) and smaller DIFFAXIS (p< 0.05) were associated with a failed fit. For failures caused by physical fit of a selected base curve, a smaller DIFFAXIS (p< 0.05), larger steep SimKs2b (p< 0.05), and larger DIFFASTIG (p< 0.01) were associated with a failed fit.

CONCLUSIONS

Novel quantitative descriptors of corneal shape and toricity derived from topography are associated with empirical soft toric contact lens fitting failures. Future algorithms or recommendations for improved soft toric lens selection may be derived from such indices to develop a predictive model for successful soft toric lens fitting using corneal topography data.

目的

基于显验光和角膜曲率计进行的经验性软性环曲面接触镜验配，在初次配镜时常常会出现意料之外的配适和屈光度误差。然而，角膜地形图可能会提供一些特征，这些特征会影响软性环曲面接触镜在原位的性能、弯曲度和后顶点屈光度，这可能有助于改进验配指导原则。在本研究中，生成并分析了定量的地形图描述符，将其作为预测软性环曲面接触镜验配成功的潜在变量。

方法

在使用EyeSys 2000（版本4.0）或Humphrey Atlas（版本A6）仪器进行角膜地形图检查后，对54例患者的105只眼进行了经验性后表面环曲面、棱镜稳定的软性接触镜验配。编写了自定义软件，从原始数据文件中生成54个单独的形状和散光定量描述符。使用逻辑回归来确定哪些变量对成功或失败的验配具有显著贡献。

结果

确定了两种类型的经验性验配失败：配适过松（n = 15）和屈光度误差（n = 17）。以下变量与验配失败相关：中央3mm区域内的平坦模拟角膜曲率（SimKf2b）、中央3mm区域内的陡峭模拟角膜曲率（SimKs2b）、中央和周边平坦子午线轴之间的差异（DIFFAXIS）以及中央和周边散光之间的差异（DIFFASTIG）。对于由屈光度误差导致的验配失败，较大的陡峭SimKs2b（p < 0.01）和较小的DIFFAXIS（p < 0.05）与验配失败相关。对于由所选基弧的物理配适导致的失败，较小的DIFFAXIS（p < 0.05）、较大的陡峭SimKs2b（p < 0.05）和较大的DIFFASTIG（p < 0.01）与验配失败相关。