Purpose:
Clinical data show that, when patients are implanted with multifocal IOLs, the subjective appearance and level of bother varies per patient. This may be partly due to the fact that each patient has different corneal aberrations. Last year we presented a pilot study, which showed that corneal aberrations have some effect on the appearance of halos on the retina. The purpose of the current study is to fully analyze the appearance of halos as a function of corneal aberrations, using a large set of eyes.
Methods:
Retinal images of extended light sources are simulated in computer-based eye models with varying corneal aberrations. In addition, corresponding eye models having no corneal aberrations were analysed. The retinal images obtained with these two sets of eye models were processed in two ways: (1) the image-correlation was calculated between the the retinal images of the aberrated eyes and the corresponding aberration-free eyes, and (2) the contrast was calculated of the difference between the halo image of the aberrated eyes and the corresponding aberration-free eyes (‘delta-image’). The outcomes were correlated with the corneal aberrations.
Results:
The retinal light intensity profiles represent a wide variety of halo appearances. The image-correlation varied between 0.847 and 0.996 (-). The RMS contrast of the delta-image varied between 18.6 and 217.6 (arbitrary units). Both metrics correlated significantly with the RMS of the higher order aberrations of the eye (P<<0.001). Significance was even greater when correlated with the polychromatic MTF Volume, and the Area under the polychromatic radial MTF.
Conclusions:
The size, shape and intensity of the multifocal halo vary with each eye. The study demonstrates that corneal aberrations have a statistically significant effect on the appearance of halos on the retina.
Keywords: aberrations • intraocular lens