Pseudophakic dysphotopsia may be associated with a small number of AcrySof lenses

The sharpened edge that prevents PCO also may cause a reflected burst of light.

Issue: November 15, 1999

VIENNA, Austria — Pseudophakic dysphotopsia is correlated with a small number of AcrySof (Alcon, Fort Worth, Texas) lenses, although only a few patients have asked for explantations as a result.

Mirror effect

--- Pseudophakic edge glare: a glare source at a given angle with respect to the visual axis at the nodal point of the pseudophakic eye will produce a refracted and a reflected image if rays are able to internally reflect from the edge of the lens. The unwanted reflected glare image will appear like a thin crescent or partial ring on the opposite side of the retina from the glare source image.
PHOTOGRAPH COURTESY OF JACK T. HOLLADAY, MD.

Ray tracing analyses suggest that the flat-edge design of the AcrySof lens creates a mirror effect that causes glare or dysphotopsia. The high refractive index also may contribute.

Randall J. Olson, MD, of the John Moran Eye Center in Salt Lake City, reported on case studies at the annual meeting of the European Society of Cataract and Refractive Surgeons.

“That’s one of the last very important areas we have to deal with in regards to enhancing patient satisfaction,” Dr. Olson said.

“In all fairness, though, this is an uncommon phenomenon,” Dr. Olson said. “This is not something that routinely is occurring. Most patients find these symptoms to be relatively minimal. However, there is a subset that finds this to be very upsetting.”

---Four common edge designs: the top two designs are non-lenticular biconvex lenses (power on both surfaces all the way to the edge), one with sharp corners (upper left) and the other with rounded corners (upper right). The bottom two lenses are lenticular biconvex, with extensions that are plano. The plano lentical may have sharp corners (lower left) or rounded corners (lower right), similar to the non-lenticular biconvex.
PHOTOGRAPH COURTESY OF JACK T. HOLLADAY, MD.

Dr. Olson conducted retrospective and prospective studies to correlate IOL types and pseudophakic dysphotopsia. Patients responded to questionnaires to rate visual sharpness, glare, near vision quality, night vision quality and overall satisfaction.

“We have meticulously been evaluating patients who are so overwhelmed by some of this dysphotopsia associated with AcrySof lenses that they have insisted that the lenses be removed,” Dr. Olson said.

He also analyzed ray tracing analysis of the lens design and did a case history for each of more than 10 patients who asked for explantations. The most severe cases were solved by exchanging the IOL for a round-edge PMMA lens. Highly observant patients and those with large pupils may be more susceptible. Younger, myopic patients or those who received a 5.5-mm optic model of the MA30 also are suspected. However, pilocarpine has not helped patients reduce the symptoms, Dr. Olson said.

Squared edges cited

“Around the squared edge, dispersive images of getting into the lens will result in a very specific reflection,” Dr. Olson said. “And that is perceived as either a flash or an arc. So people will not have to look at light at night, but you can look off to the side and get this flash.”

The internal reflectivity seems to be a relatively minor complaint, he added.

Selected ray tracing through four edge designs using three groups of rays: rays that miss the lens; rays that are refracted by the anterior surface, internally reflected by the edge and then refracted by the posterior surface; and rays that are refracted by both surfaces. Selected ray tracing for non-lenticular lenses (left) and lenticular lenses (right). Notice the dispersion of the internally reflected rays in both cases with rounded corners.
PHOTOGRAPH COURTESY OF JACK T. HOLLADAY, MD.

AcrySof’s advantage of reducing posterior capsule opacification (PCO) may actually be a drawback in this study population. Some opacification around the edges may reduce the incidence of glare and dysphotopsia in those eyes.

Good anterior capsular fibrosis will cover the IOL edge and eliminate the dysphotopsia centrally. AcrySof tends to retard anterior capsule opacification.

“I’m sure there are patients who do get better though, because if the capsule is significantly opacified, you can eliminate this problem,” Dr. Olson said.

“Dysphotopsia is an issue,” Dr. Olson said. “The flattened edge may come with a price, but there may be a way of engineering that flattened edge that doesn’t result in dysphotopsia. I think we have to look at that, and other materials issues, so we can get better vision for our patients.”



Energy distribution and retinal image formed by the four edge designs. The rounding of a non-lenticular biconvex design (top left). Creating an extension (lenticular biconvex) for designs with sharp edges (right). Combined effect of edge rounding and lentical (bottom left). PHOTOGRAPH COURTESY OF JACK T. HOLLADAY, MD.

For Your Information:

Randall J. Olson, MD, practices at the John Moran Eye Center, 50 N. Medical Drive, Salt Lake City, UT 84132; (810) 585-6622; fax: (801) 581-3357; e-mail: randall.olson@hsc.utah.edu. Dr. Olson did not participate in the preparation of this article.