Simulated ocular biometry effects on add-power demand in multifocal intraocular lenses

To use ray-tracing simulations to assess the dependency of add-power demand on ocular biometry.

David J. Apple Laboratory for Ocular Pathology, Department of Ophthalmology, University of Heidelberg, Heidelberg, Germany.

Experimental study.

Optical biometry of 34 patients scheduled for routine cataract surgery was collected and the following parameters used to build a personalized eye model: keratometry (K), anterior chamber depth (ACD), and axial length (AL). Ray-tracing software was applied for pseudophakic-eye simulations. Each model featured a biconvex lens with radii of curvature adjusted for best distance vision. Trial spectacles with -4 diopters (D), -3 D, -2 D, and -1.5 D were placed in front of a virtual eye. The intraocular lens (IOL)-power change required to induce a desirable near/intermediate effect at the spectacle plane was calculated for the far-point condition.

Mean values for K, ACD, and AL were 7.79 ± 0.24 mm, 3.22 ± 0.60 mm, and 23.77 ± 1.34 mm, respectively. The lowest and highest add power (IOL plane) varied by 0.39 D, 0.52 D, 0.76 D, and 0.98 D for -1.5 D, -2 D, -3 D, and -4 D trial spectacles, respectively. High correlation was found between the observed add-power change and the ACD, indicating a linear increase of the add-power demand for larger ACD values. The AL and the K demonstrated poor or no correlation with the required IOL-power adjustment.

The ACD, which determines the effective lens position in our model, has greater impact on add-power demand than AL or K. The reported change may contribute to interparticipant variability in defocus curves of multifocal patients.