Purpose : Intraocular lens (IOLs) implantation in cataract surgery is a safe and effective procedure to substitute the cataractous crystalline lens. However, current IOLs have very different shapes and optical properties compared with the natural lens that may produce image distortion. This study pertains to the theoretical and experimental study of the different magnifications of the retinal image in the periphery of the pseudophakic eye.
Methods : A model eye was used to calculate the image location on the retina for different anatomical parameters (corneal power, axial length, anterior chamber depth, retinal radius of curvature) and intraocular lens (IOL) power. These locations were compared to those of the intact (phakic) eye. In addition, fundus photography (Cobra HD, SCO, Italy) was performed in a series of 52 mild cataract patients preoperatively and one month postoperatively. Each pair of images was comparatively analysed using a purposely-written script in MATLAB (MathWorks, Natick, MA, USA). The script allowed supervised image registration with control points allowing rotation and provided an estimation of the relative radial displacement of the retinal features.
Results : Optical modeling revealed the conditions at which distortion is induced by IOL implantation. The most important parameters are the IOL power, the retinal curvature and the pseudophakic anterior chamber depth. Image analysis in the patient group revealed that the radial displacement ranged from 0 to 2.2 degrees (mean:1.12, SD: 0.58) in a field of up to 40 degrees. The relative magnification was not constant at all field angles indicating an induced positive -Pincushion type- distortion. These experimental findings were consistent with the optical modelling.
Conclusions : We found abnormal image magnification and distortion in the central 40 degrees of the visual field in pseudophakic eyes. Although this is not having any practical implications for central vision, peripheral image is distorted by several degrees depending on the anatomical parameters of the eye and the characteristics of the IOL. These results also indicate that current IOLs are not optimized for peripheral distortion. Further research is required to determine whether this phenomenon affects the quality of peripheral vision of pseudophakic patients.
This is a 2020 ARVO Annual Meeting abstract.