[Interpretation of the Intraocular Lens Constants for the Haigis Formula]

Background The Haigis formula uses a linear regression with three IOL constants for the prediction of the effective lens position (ELP) of the intraocular lens (IOL), ELP ≈ a₀ + a₁ ACD + a₂ L. It is based on the preoperative anterior chamber depth (ACD) and axial length (L). Material and Methods Differences between IOL constant triplets can be judged based on their statistical measurement uncertainty. To investigate, if the estimation of the average ELP with the help of the average ACD and average L according to 〈ELP〉 ≈ a₀ + a₁ 〈ACD〉 + a₂ 〈L〉 provides a possible alternative, we have compared both methods. The results based on two different strategies for optimisation of the IOL constants a₀, a₁, a₂ are used for illustration. Results The estimation of the average ELP is suitable for basic categorisation of the IOL constants. The confidence-volumes in shape of ellipsoids based on the statistical measurement uncertainties of the IOL constant optimisations allow a better comparison between IOL constant triplets a₀, a₁, a₂.