Accommodating IOL delivers full range of vision, contrast sensitivity

The lens shifts in a myopic direction as the pupil constricts in photopic conditions.

Issue: August 25, 2010

A monofocal accommodating IOL enhances depth of focus and quality of vision, according to a speaker at Hawaiian Eye 2010.

Two current Crystalens models, the HD and 5.0 (Bausch + Lomb), offer a full range of vision and maintain contrast sensitivity. The Crystalens Aspheric Optic (AO) IOL, a new variant that launched in January, may further enhance quality of vision, Richard L. Lindstrom, MD, said.

The Crystalens is the only accommodating IOL approved by the U.S. Food and Drug Administration.

Pupil size and refraction

The Crystalens HD, a blended bispheric monofocal accommodating IOL, offers “excellent depth of focus with superior quality of vision,” Dr. Lindstrom said.

It features a 1.5-mm 1 D addition at the center of the standard 5.0 optic.

“It adds a small amount of power centrally,” he said. “It is then tumble-polished, which basically smoothes it over. And it’s really not an aspheric lens exactly, but with the blending it does have some behavior similar to an aspheric lens and it does potentially induce some negative spherical aberration when the pupil is small.”

Dr. Lindstrom said that in bright light, as the pupil constricts, the Crystalens HD shifts toward a myopic correction and the Crystalens 5.0 shifts toward a hyperopic correction.

“If you want to read, when the pupil is small in a bright light environment, we’d rather shift minus,” he said. “So that’s what was done to try to make the Crystalens HD give better near vision in a standard environmental setting where you’re typically reading. Now, this doesn’t help near vision a lot when you have a 5-mm pupil in a dark restaurant. It shifts more toward minus as the pupil constricts, and it should therefore enhance near vision in the typical reading environment, which is bright light and while accommodating.”

Contrast sensitivity and distance vision

In testing, the Crystalens HD yielded better contrast sensitivity than the Crystalens AT-45 in mesopic illumination without glare, Dr. Lindstrom said.

In addition, it offered slightly better contrast sensitivity than the AT-45 in mesopic illumination with glare and provided better distance visual acuity, he said.

“There’s no evidence of any loss of quality of distance vision, at least in this large cohort of patients, and this is thousands of patients,” he said. “We would expect the HD to do a little bit better at intermediate. … It does appear to be slightly superior at intermediate, but both of these lenses perform better than the typical multifocal competition.”

The Crystalens HD improved uncorrected near visual acuity to J1 in 55% of patients, Dr. Lindstrom said.

“What we wanted to get was better near vision,” he said. “We are still debating a little bit how we should define accommodation. Does a pupil getting smaller and increasing depth of focus as you look at something near — is that accommodation or does the lens have to change shape? In the end, what the patient wants to do is be able to read, and the Crystalens HD did make a significant improvement in near acuity vs. the Crystalens 5.0 and AT-45.” – by Matt Hasson

Richard L. Lindstrom, MD, can be reached at Minnesota Eye Consultants, 9801 DuPont Ave. S, Suite 200, Bloomington, MN 55431; 952-888-5800; fax: 952-567-6182; e-mail: rllindstrom@mneye.com. Dr. Lindstrom is a consultant for Bausch + Lomb.