Intraocular lens implantation position sensitivity as a function of refractive error.

PURPOSE To quantify the change in ocular aberrations due to intraocular lens (IOL) implantation position errors for pseudo-phakic eyes with different refractive errors. METHODS The theoretical part of this work was based on ray-tracing in emmetropic and myopic eye models. The possible misalignments i.e. the decentration, tilt and axial translation, of the IOLs were statistically combined together and analysed using Monte-Carlo simulations. Spherical IOLs with a 3 and 5 mm pupil and an aspheric IOL with a 5 mm pupil were analysed as a function of refractive error. In the experimental part of the work, we built an IOL optical test bench including a model eye. The white light discrete point spread functions of misaligned IOLs were recorded by a CCD and we compared the change of the spread function as a result of misalignments for two spherical IOLs with different optical powers. RESULTS The Monte-Carlo simulations showed that the average root-mean-square spot size at the retinal plane decreased with increasing myopic refractive error, i.e. lower power IOL. The experiments showed that a lower optical power spherical IOL had a less distributed point spread function than a higher optical power IOL, which supported the results of the simulation. CONCLUSION Regarding IOLs designed for myopic patients, low power IOLs (for high myopes) were shown to be less sensitive to the misalignment than high power ones. Aspheric IOLs were more sensitive to position errors than spherical IOLs under the same conditions.