From the Department of Experimental Ophthalmology, Saarland University, Homburg/Saar, Germany (Langenbucher, Wendelstein); Augen- und Laserklinik Castrop-Rauxel, Castrop-Rauxel, Germany (Hoffmann); School of Physical Sciences, The Open University, Milton Keynes, United Kingdom (Cayless); Department of Ophthalmology, Johannes Kepler University Linz, Linz, Austria (Wendelstein); Dr. Rolf M. Schwiete Center for Limbal Stem Cell and Aniridia Research, Saarland University, Homburg/Saar, Germany (Szentmáry); Department of Ophthalmology, Semmelweis-University, Budapest, Hungary (Szentmáry).
J Cataract Refract Surg. 2024 Apr 1;50(4):360-368. doi: 10.1097/j.jcrs.0000000000001363.
To investigate and compare different strategies of corneal power calculations using keratometry, paraxial thick lens calculations and ray tracing.
Tertiary care center.
Retrospective single-center consecutive case series.
Using a dataset with 9780 eyes of 9780 patients from a cataractous population the corneal front (Ra/Qa) and back (Rp/Qp) surface radius/asphericity, central corneal thickness (CCT), and entrance pupil size (PUP) were recorded using the Casia 2 tomographer. Beside keratometry with the Zeiss (PK Z ) and Javal (PK J ) keratometer index, a thick lens paraxial formula (PG) and ray tracing (PR) was implemented to extract corneal power for pupil sizes from 2 mm to 5 mm in steps of 1 mm and PUP.
With PUP PK Z /PK J overestimates the paraxial corneal power PG in around 97%/99% of cases and PR in around 80% to 85%/99%. PR is around 1/6 or 5/6 diopters (D) lower compared with PK Z or PK J . For a 2 mm pupil PR is around 0.20/0.91 D lower compared with PK Z /PK J and for a 5 mm pupil PR is comparable with PK Z (around 0.03 D lower) but around 0.70 to 0.75 D lower than PK J .
"True" values of corneal power are mostly required in lens power calculations before cataract surgery, and overestimation of corneal power could induce trend errors in refractive outcome with axial length and lens power if compensated with the effective lens position.
研究和比较角膜曲率计、傍轴厚透镜计算和光线追踪在角膜力计算中的不同策略。
三级保健中心。
回顾性单中心连续病例系列。
使用来自白内障人群的 9780 例 9780 只眼的数据集，使用 Casia 2 断层扫描仪记录角膜前表面（Ra/Qa）和后表面（Rp/Qp）半径/非球面度、中央角膜厚度（CCT）和瞳孔入口大小（PUP）。除了使用蔡司（PK Z）和 Javal（PK J）角膜曲率计指数进行角膜曲率测量外，还实施了厚透镜傍轴公式（PG）和光线追踪（PR），以从 2 毫米到 5 毫米的瞳孔大小步长为 1 毫米和 PUP 提取角膜力。
对于 PUP，PK Z/PK J 在大约 97%/99%的情况下高估了傍轴角膜力 PG，在大约 80%到 85%/99%的情况下高估了 PR。与 PK Z 或 PK J 相比，PR 低约 1/6 或 5/6 屈光度（D）。对于 2 毫米的瞳孔，PR 比 PK Z/PK J 低约 0.20/0.91 D，对于 5 毫米的瞳孔，PR 与 PK Z 相当（低约 0.03 D），但比 PK J 低约 0.70 至 0.75 D。
在白内障手术前的镜片功率计算中，大多需要“真实”的角膜功率值，如果用有效透镜位置来补偿，角膜功率的高估可能会导致轴向长度和透镜功率的屈光结果出现趋势误差。
