Patients’ high expectations for cataract surgery outcomes continue to be bedeviled by the visual phenomena known as dysphotopsias. At Friday’s Refractive Surgery Subspecialty Day, Jack T. Holladay, MD, offered an overview of how to categorize and address these visual disturbances.
Entoptic phenomena. “This is simple: The patient sees a flash with his eyes closed. Well, that goes to retina,” Dr. Holladay said. That’s because these phenomena are not related to the IOL; instead, they are related to a partial peripheral or central vitreous collapse that causes traction on the retina.
Negative dysphotopsia. “These are also easy for refractive surgeons to evaluate,” Dr. Holladay said. Patients typically report a dark arcuate line or dark area in the extreme periphery of their vision. In ray-tracing studies, Dr. Holladay found that this shadow occurs when there’s a gap between the light rays that are refracted by the IOL and those that miss the IOL’s optic and go to one part of the periphery. Both patient factors (including small pupils and high IOL power) and IOL design issues (most notably, truncated edges) can contribute to this problem.
Most cases of negative dysphotopsia resolve shortly after surgery; those that don’t can be treated with removal of the nasal overlapping capsule, reverse optic capture, or IOL exchange, he said.
Positive dysphotopsia. These include halos, glare, and streaks of light and may be connected to either patient factors or IOL optics.
With regard to patient factors, Dr. Holladay highlighted “chord mu (µ),” a new reference marker that can be calculated with the help of a biometric device. If the chord µ value is greater than 0.6 mm, “the optical performance of a diffractive IOL is going to be poor—so you shouldn’t put one in,” he said. Wavefront topography can also help flag those patients likely to be affected by positive dysphotopsia, Dr. Holladay said. And with regard to IOL factors, diffractive optics and truncated edge designs can be problematic; in these instances, lens exchange is the only treatment option. —Jean Shaw
Financial disclosures. Dr. Holladay: AcuFocus: C,O; Alcon: C; AMO: C; ArcScan: C,O; Carl Zeiss: C; MST: C; Oculus: C; RxSight: C,O; Visiometrics: C,O.
Disclosure key. C = Consultant/Advisor; E = Employee; L = Speakers bureau; O = Equity owner; P = Patents/Royalty; S = Grant support.
Read more news from AAO 2019 and the Subspecialty Day meetings.