Internet database IOLCon, a provider of IOL constants and specifications, recently launched the free "Lens Power Calculation Module (LPCM)," to support ophthalmic surgeons.

Optimizing of Constants

The method used by IOLCon is characterized as an "intelligent IOL constant optimization." Statistical methods are used to take the measuring accuracy of the instruments into account (e.g. biometer). Optimizations of the constants for the following published formulas can be found on IOLCon: Haigis, Hoffer-Q, Holladay 1, SRK/T, and also for the new Castrop formula.

Lens Power Calculation Module

With the Castrop formula, a new formula for calculating IOL power recently became available. In this formula, the position of the IOL is predicted regressively using real historical measurement data (based on about 2,000 data sets). The prerequisite is the use of current techniques that precisely measure all distances of the eye. With this data (in connection with modern formulae such as the Castrop formula), even eyes that are outside the norm and which might cause difficulties when using classic formulae, can be calculated more reliably.

More information regarding the Castrop formula, which is already available as a toric variant, was recently published also as Open Access articles:

  • Langenbucher et al, Considerations on the Castrop formula for calculation of intraocular lens power, PLoS One, 2021, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8172026/
  • Langenbucher et al, The Castrop formula for calculation of toric intraocular lenses, Graefe's Archive for Clinical and Experimental Ophthalmology, November 2021, https://link.springer.com/article/10.1007/s00417-021-05287-w
  • Wendelstein et al., Project hyperopic power prediction: accuracy of 13 different concepts for intraocular lens calculation in short eyes, BJO 2021, https://bjo.bmj.com/content/early/2021/01/26/bjophthalmol-2020-318272

The new "Lens Power Calculation Module" is based on the Castrop formula (available as an online tool via the IOLCon website). This tool can be accessed via the "LPCM" button on the IOLCon landing page (Fig. 1) After accepting the terms of use, (Fig. 2) the Lens Power Calculation Module can be used directly (Fig. 3).