Experimental Ophthalmology, Saarland University, Kirrberger Str. 100, Bldg 22, 66424 Homburg, Germany; Erlangen Graduate School in Advanced Optical Technologies, Paul-Gordan-Str. 6, 91052 Erlangen, Germany.
Experimental Ophthalmology, Saarland University, Kirrberger Str. 100, Bldg 22, 66424 Homburg, Germany.
Z Med Phys. 2014 May;24(2):94-103. doi: 10.1016/j.zemedi.2013.05.001. Epub 2013 Jun 6.
BACKGROUND & PURPOSE: Implantation of an artificial intraocular lens (IOL) during cataract surgery significantly changes the balance of aberrations in the eye. We demonstrate the theoretical superiority of customized aspheric IOL designs over standard spherical IOLs for different values of corneal curvature, asphericity and axial length.
For a selected set of corneal surfaces we calculated a best-fit equiconvex spherical IOL. In a second step we customized the IOL back surface to correct the wavefront aberrations of the cornea. Then we calculated a quadric approximation of the IOL back surface to retrieve the aspheric parameters of the customized lens in terms of radius of curvature and asphericity/conic constant. The optical performance of the three IOL models was monitored in terms of lateral ray spread (LRS) at retinal plane for variations of corneal curvatures, asphericity and axial lengths of the pseudophakic eye.
The LRS of customized aspheric IOLs was significantly smaller compared to that of spherical IOLs (typically between 10 and 25 dB). For high aspheric coefficients the LRS increased with spherical IOLs. With aspheric IOLs LRS was higher for steep corneas paired with high aspheric coefficients, mostly due to the fitting error of the quadratic function. For several combinations of corneal curvature and aspheric coefficients the focal point of the aspheric IOL was up to 400 times smaller than the spherical one.
This study appeals to the reader for the potential benefit of customized aspheric IOL design instead of the principle of a 'one size fits all' aspheric coefficient as used currently in clinical practice. A benefit with customized IOLs is less depending from the axial length and can be achieved with corneas of a moderate prolate aspheric shape with an equal or more negative Q value than the average of -0.22. Longer eyes seem to benefit less than short eyes.
白内障手术中人工晶状体（IOL）的植入会显著改变眼球像差的平衡。我们展示了定制非球面 IOL 设计相对于标准球面 IOL 在不同角膜曲率、非球面度和眼轴长度值下的理论优势。
对于一组选定的角膜表面，我们计算了最佳拟合的共焦球面 IOL。在第二步中，我们定制了 IOL 的后表面以校正角膜的波前像差。然后，我们计算了 IOL 后表面的二次近似，以恢复定制透镜的非球面参数，即曲率半径和非球面度/圆锥常数。在模拟的无晶状体眼中，我们监测了三种 IOL 模型的光学性能，以视网膜平面上的横向射线扩展（LRS）来表示角膜曲率、非球面度和眼轴长度的变化。
定制非球面 IOL 的 LRS 明显小于球面 IOL（通常在 10 到 25dB 之间）。对于高非球系数，LRS 随球面 IOL 增加而增加。对于陡峭的角膜与高非球系数配对的情况，LRS 随着非球面 IOL 而增加，这主要是由于二次函数拟合误差所致。对于角膜曲率和非球系数的几个组合，非球面 IOL 的焦点可以小到球面 IOL 的 400 倍。
这项研究呼吁读者关注定制非球面 IOL 设计的潜在优势，而不是目前临床实践中使用的“一刀切”非球系数原则。与定制 IOL 相关的一个优势是，它对眼轴长度的依赖性较小，并且可以在具有中等拉长非球面形状的角膜上实现，其 Q 值与-0.22 的平均值相等或更负。长眼似乎比短眼受益较小。
