Simulated Ocular Biometry Effects on Add-Power Demand in Multifocal Intraocular Lenses.

Purpose: There is inter-subject variability in position of secondary peaks in defocus-curves among patients who received the same multifocal intraocular lens (IOL). This study used ray-tracing simulations to assess the dependency of add-power demand on ocular biometry.

Setting: David J. Apple Laboratory for Ocular Pathology.

Design: Experimental study.

Methods: 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 glasses with -4D, -3D, -2D, and -1.5D were placed in front of a virtual eye. The IOL-power change required to induce a desirable near/intermediate effect at the spectacle plane was calculated with respect to the far-point condition.

Results: Mean values for K, ACD, and AL were 7.79±0.24mm, 3.22±0.60mm, and 23.77±1.34mm, respectively. The lowest and highest add power (IOL plane) varied by 0.39D, 0.52D, 0.76D, 0.98D for -1.5D, -2D, -3D and -4D trial glasses, 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.

Conclusions: 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 inter-subject variability in defocus curves of multifocal patients.