Abstract
Purpose :
Negative dysphotopsia (ND) encompasses a group of subjective complaints from pseudophakic patients related to the perception of dark crescent shadows in the peripheral field of view. Several biometric factors (pupil size in photopic conditions, angle kappa, hyperopia etc) and intraocular lens characteristics (IOL, tilt and decentration, optic body size etc) were previously evaluated to elucidate potential underlying mechanisms of ND. The current study describes a theoretical eye model enabling the evaluation of ND in conditions matching clinically realistic situations.
Methods :
Based on a customized theoretical eye model, a non-sequential eye model (NSC-EM) was constructed with the IOL modelled as a 3D object. The IOL edge scattering was implemented by using a retro-fitted Lambertian scattering surface. For the current study, similar IOL models from three different manufacturers were evaluated. Using a wide angle white light source and a spherical detector mimicking the retina with an angular extent higher than 90 degrees, irradiance maps and cross-sectional irradiance profiles were computed for 2.0 and 2.5 mm pupil diameters.
Results :
For both pupil sizes, the NSC-EM irradiance maps evidenced the retinal illumination gap between light refracted by the IOL and light refracted by the cornea only. The simulated ND profiles showed a peripheral location of the shadows at approximately 75 degrees and a 0.4 decades lower minimum irradiance for the smaller pupil diameter. These results are aligned with descriptions of ND complaints in the literature. The IOLs from the three manufacturers had similar mechanical platforms (i.e. 1-piece, similar optic diameter, overall diameter and haptic design) but different optic edge designs (i.e. geometry, thickness, refractive index, roughness). These different IOL models were characterized by comparable ND profiles with the peripheral location of the shadows between 69 and 76 degrees.
Conclusions :
The eye model results are clinically pertinent in terms of both angular location and pupil dependency of ND. The theoretical results from this study demonstrate that in identical biometrical conditions, different edge designs are characterized by comparable ND profiles.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.