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.
The etiology of negative dysphotopsias involves the spatial relationships between the IOL, the capsular bag, and possibly the iris. IOLs implanted in the capsular bag or in the posterior chamber are more likely to produce negative dysphotopsias while IOLs implanted in the sulcus or in the anterior chamber seldom do.
Ray tracing suggests that at least part of the problem lies with internal reflections when the lens is placed in the capsular bag that can cast temporal shadows. Other potential factors include corneal curvature, anterior chamber depth, IOL power, axial length and the distance between the pupil and the implant.
“Negative dysphotopsias are seen more frequently in patients who have a square edge IOL,” Dr. Mamalis said. “It can occur with any lens material, though we see it more frequently with hydrophobic acrylic.”
Treatment typically involves IOL exchange and implantation of a new lens into the sulcus. Piggyback, or add-on, IOLs can also help alleviate negative dysphotopsias by diffusing light more effectively before it enters the eye, reducing the potential for shadow formation.
Reverse optic capture, placing the optic over the edges of the capsular bag instead of in the bag, can also help. And some surgeons perform laser anterior capsulotomy to enlarge the capsule opening.
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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.