Optical Characterization Method for Tilted or Decentered Intraocular Lenses.

Abstract

To test and validate a method for measuring the optical quality and optical power of monofocal intraocular lenses (IOLs) in the presence of a tilt or a decentration as well as its optical power. The experimental system consists of an artificial eye (wet-cell) and a commercial aberrometer with a Shack-Hartmann sensor. Optical image quality parameters such as point spread function (PSF), modulation transfer function (MTF), and the simulations of the retinal image of an extended object are computed from the in vitro wavefront data of an IOL. Repeatability and reproducibility of the system are tested. Mathematical and ray-tracing simulations are used to ascertain the precision and accuracy of the method. Comparison with a standard single-pass method of measurement is also made. Optical properties of four commercial monofocal IOLs are measured under tilts of 0°, 2°, and 4°, and vertical decentrations of 0, 0.2, and 0.4 mm; the results of such measurements are compared with a ray-tracing simulation. Precision and accuracy of the system are in good agreement with theoretical calculations. Reproducibility and repeatability are within standard ISO norms. MTFs obtained with this method and with the standard method are very similar. The precision of the estimation of the IOL's optical power is higher than 98.6%. Commercially tested IOLs show a decrease of optical quality in the presence of decentrations and tilts, and their susceptibility to tilts and decentrations depends on the asphericity. These results are in concordance with the results obtained by ray-tracing simulation. A simple wavefront-based method for in vitro measurements of the wavefront aberrations and power of an IOL is proposed and tested showing accurate and precise results.