Abstract
Purpose :
Negative dysphotopsia (ND) is an entoptic phenomenon affecting pseudophakic eyes where a crescent-shaped shadow is perceived at the far peripheral visual field. Various studies have indicated that the mechanism of ND involves the light transmitted without being focused by the intraocular lens (IOL), i.e. transmitted through the gap between the IOL’s optic and the posterior surface of the iris of the eye. In this study we investigate how affect ND the particular design of IOLs and in particular how inverted meniscus lenses can prevent this phenomenon.
Methods :
We used a physical model of the pseudophakic eye in conjunction with an extended light source implemented using a computer screen to compare ND occurrence and severity between biconvex and inverted meniscus lenses. The eye model had a PMMA cornea (R=7.73mm, Q= -0.24) an iris at a depth of 3.55mm and an IOL holder introducing the IOL at a distance of 1.5mm from the pupil (pseudophakic anterior chamber depth of 5.05 mm). The eye was filled with distilled water. A camera (72BUC02-ML, Imaging Source, Germany) in a water-tight container was used to record the retinal images. To evaluate dysphotopsia a horizontal bar (5ο x 15ο) was presented at the peripheral field of view (70ο to 85ο). Images at the retinal plane were assessed with respect to the occurrence and severity of a shadow near the edge of the visual field. Negative dysphotopsia was investigated for two different types of IOLs, one with a standard biconvex design (Acrysof SN60WF, Alcon, TX USA and other with a newly designed inverted meniscus shape (ArtIOL, Art25, Voptica SL, Murcia, Spain), for a pACD value of 5.05 mm and for two different pupil diameters (3 and 6 mm).
Results :
A characteristic shadow appeared on the peripheral retinal image with the biconvex IOL. The effect was more pronounced in the smaller (3mm) pupil diameter than with the larger (6 mm). The shadow did not occur with the inverted meniscus shaped IOLs with either pupil diameter.
Conclusions :
Negative dysphotopsia can be reduced or eliminated with inverted meniscus shaped IOLs. This finding is consistent with non-sequential optical modelling. For a given implantation depth the meniscus shape has an inherently narrower peripheral gap between the IOL’s optic and the posterior iris, therefore it is less likely to cause negative dysphotopsia. This will result in a greater visual comfort for patients after cataract surgery.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.