Department of Experimental Ophthalmology, Saarland University, Kirrberger Str 100 Bldg. 22, 66424, Homburg/Saar, Germany.
Dr. Rolf M. Schwiete Center for Limbal Stem Cell and Aniridia Research, Saarland University, Homburg/Saar, Germany.
Graefes Arch Clin Exp Ophthalmol. 2021 Nov;259(11):3321-3331. doi: 10.1007/s00417-021-05287-w. Epub 2021 Jul 8.
To explain the concept behind the Castrop toric lens (tIOL) power calculation formula and demonstrate its application in clinical examples.
The Castrop vergence formula is based on a pseudophakic model eye with four refractive surfaces and three formula constants. All four surfaces (spectacle correction, corneal front and back surface, and toric lens implant) are expressed as spherocylindrical vergences. With tomographic data for the corneal front and back surface, these data are considered to define the thick lens model for the cornea exactly. With front surface data only, the back surface is defined from the front surface and a fixed ratio of radii and corneal thickness as preset. Spectacle correction can be predicted with an inverse calculation.
Three clinical examples are presented to show the applicability of this calculation concept. In the 1st example, we derived the tIOL power for a spherocylindrical target refraction and corneal tomography data of corneal front and back surface. In the 2nd example, we calculated the tIOL power with keratometric data from corneal front surface measurements, and considered a surgically induced astigmatism and a correction for the corneal back surface astigmatism. In the 3rd example, we predicted the spherocylindrical power of spectacle refraction after implantation of any toric lens with an inverse calculation.
The Castrop formula for toric lenses is a generalization of the Castrop formula based on spherocylindrical vergences. The application in clinical studies is needed to prove the potential of this new concept.
解释 Castrop 散光人工晶状体（tIOL）计算公式背后的概念，并展示其在临床实例中的应用。
Castrop 光轴公式基于一个具有四个折射面和三个公式常数的无晶状体模型眼。所有四个面（眼镜矫正、角膜前表面和后表面以及散光人工晶状体）都用球柱面光轴表示。利用角膜前表面和后表面的断层扫描数据，可以准确地将这些数据视为定义角膜厚透镜模型的参数。仅从前表面数据出发，可以根据前表面和固定的半径和角膜厚度比来定义后表面。眼镜矫正可以通过反演计算来预测。
提出了三个临床实例来说明这种计算概念的适用性。在第一个实例中，我们根据球柱面目标折射和角膜前表面和后表面的断层扫描数据，推导出了 tIOL 屈光力。在第二个实例中，我们根据角膜前表面的角膜曲率计数据计算了 tIOL 屈光力，并考虑了手术诱导的散光和角膜后表面散光的矫正。在第三个实例中，我们通过反演计算预测了任何散光人工晶状体植入后的球柱面眼镜折射力。
Castrop 散光人工晶状体公式是基于球柱面光轴的 Castrop 公式的推广。需要在临床研究中应用来证明这个新概念的潜力。
