Clinician explains negative dysphotopsia origin, treatment

Jack T. Holladay

ROME — Negative dysphotopsia, which patients describe as a dark, crescent-shaped temporal shadow that increases with bright light, has an explanation and can be treated, according to a speaker here.

Negative dysphotopsia after IOL implantation was the topic of the Benedetto Strampelli Medal Lecture given by Jack T. Holladay, MD, MSEE, FACS, at the annual joint meeting of Ocular Surgery News and the Italian Society of Ophthalmology.

"Two rays, coming in from the temporal side at 90°, are bent by the cornea by about 45°. As they come through, one ray, if there is a space between the iris and the anterior surface of the lens, can miss the front part of the lens, while the other ray hits the lens and is bent by the lens's refractive power. In the cone between those two rays, no light can enter, and this causes what is perceived by the patient as a crescent-shaped shadow," Dr. Holladay said.

In the first day after IOL implantation, approximately 15% of patients experience negative dysphotopsia. By 3 years, the phenomenon is reduced to only 5%, he said.

"To treat negative dysphotopsia, we have to eliminate the rays that pass anterior to the IOL, and to do so we have to reduce the space between the iris and the anterior surface of the IOL," Dr. Holladay said.

This reduction may occur spontaneously in some cases with the natural forward movement of the IOL after capsular bag contraction. The opacification of the temporal sulcus, occurring naturally several weeks or months after implantation, is also likely to reduce the shadow effect.

"You can otherwise flip the optic, though this might induce myopia, or you can implant a piggyback IOL in the sulcus. Frosted-edge IOLs are another solution," Dr. Holladay said.

Disclosure: No products or companies are mentioned that would require financial disclosure.