Medical Optics at the Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany.
Curr Eye Res. 2011 Jun;36(6):579-89. doi: 10.3109/02713683.2011.566978.
To provide a mathematical calculation scheme for customized intraocular lens (IOL) design based on high resolution anterior segment optical coherence tomography (AS-OCT) of anterior eye segment and axial length data.
We use the corneal and anterior segment data from the high resolution AS-OCT and the axial length data from the IOLMaster to create a pseudophakic eye model. An inverse calculation algorithm for the IOL back surface optimization is introduced. We employ free form surface representation (bi-cubic spline) for the corneal and IOL surface. The merit of this strategy is demonstrated by comparing with a standard spherical model and quadratic function. Four models are calculated: (1) quadratic cornea + quadratic IOL; (2) spline cornea + quadratic IOL; (3) spline cornea + spline IOL; and (4) spherical cornea + spherical IOL. The IOL optimization process for the pseudophakic eye is performed by numerical ray-tracing method within a 6-mm zone. The spot diagram on the fovea (forward ray-tracing) and wavefront at the spectacle plane (backward ray-tracing) are compared for different models respectively.
The models with quadratic (1) or spline (3) surface representation showed superior image performance than the spherical model 4. The residual wavefront errors (peak to valley) of models 1, 2, and 3 are below one micron scale. Model 4 showed max wavefront error of about 15 µm peak to valley. However, the combination of quadratic best fit IOL with the free form cornea (model 2) showed one magnitude smaller wavefront error than the spherical representation of both surfaces (model 3). This results from higher order terms in cornea height profile.
A four-surface eye model using a numerical ray-tracing method is proposed for customized IOL calculation. High resolution OCT data can be used as a sufficient base for a customized IOL characterization.
提供一种基于高分辨率眼前节光学相干断层扫描（AS-OCT）和眼轴长度数据的定制人工晶状体（IOL）设计的数学计算方案。
我们使用高分辨率 AS-OCT 的角膜和眼前节数据以及 IOLMaster 的眼轴长度数据来创建一个无晶状体眼模型。引入了用于优化 IOL 后表面的逆计算算法。我们采用自由曲面表示（双三次样条）表示角膜和 IOL 表面。通过与标准的球形模型和二次函数进行比较，验证了该策略的优势。计算了四个模型：（1）二次角膜+二次 IOL；（2）样条角膜+二次 IOL；（3）样条角膜+样条 IOL；和（4）球形角膜+球形 IOL。通过在 6mm 范围内的数值光线追踪方法对人工晶状体进行优化。比较了不同模型的黄斑区（前向光线追踪）和眼镜平面（后向光线追踪）上的光斑图。
具有二次（1）或样条（3）表面表示的模型比球形模型 4 具有更好的图像性能。模型 1、2 和 3 的残余波前误差（峰谷）均低于一微米。模型 4 的最大波前误差约为 15μm 峰谷。然而，二次最佳拟合 IOL 与自由曲面角膜（模型 2）的组合显示出比两个表面的球形表示（模型 3）小一个数量级的波前误差。这是由于角膜高度轮廓的高阶项。
提出了一种使用数值光线追踪方法的四表面眼模型，用于定制 IOL 计算。高分辨率 OCT 数据可用作定制 IOL 特征化的充分基础。
