Don’t discount dysphotopsias, either positive or negative, after cataract surgery and IOL placement. The literature suggests that dysphotopsias are relatively rare, but patient reports suggest a different story.
Positive dysphotopsias are most often characterized by persistent bright rings, flares, arcs, halos, and flashes that most often appear when light is coming into the eye from the side, such as the oncoming headlights of another vehicle. The long term incidence may be as high as 1.5% and can vary greatly by IOL type, material, and design.
Positive dysphotopsia was first reported in polymethylmethacrylate (PMMA), the material most commonly used during the early development of IOLs. Symptoms were generally minor glare and transient.
Hydrophobic acrylic lenses are more prone to positive dysphotopsia. The higher index of refraction is more likely to result in internal reflections when exposed to bright sources.
Silicone lenses are rarely associated with positive dysphotopsia, possibly because of lens design. Lenses with square edges, typically hydrophobic acrylic IOLs, are associated with an increased incidence of positive dysphotopsia. Frosted and textured edges as well as beveled designs have been used to reduce the intensity of stray reflections and reduce the incidence of positive dysphotopsia.
Nick Mamalis, MD
Dr. Mamalis is professor of ophthalmology, John A. Moran Eye Center, University of Utah, Salt Lake City. He did not indicate any proprietary interest in the subject matter.