Accommodating IOLs feature novel optical mechanics

Emerging optic designs and mechanical concepts represent a turn in accommodating IOL design.

The ideal accommodating lens would enhance range of vision and correct astigmatism, Y. Ralph Chu, MD, told Ocular Surgery News.

“[It would be] a lens that can restore our visual function for all ranges of vision, at least as good as what Mother Nature gave us when we were 20 or 25 years old,” Dr. Chu said. “We’re trying to achieve excellent visual optical outcomes so we don’t have the glare and halo, the loss of contrast sensitivity that some technologies bring, and yet we still maintain the range of focus that a young eye has. … Actually, the Holy Grail would be an adjustable accommodating toric lens.”

Accommodating IOL technology is only in its infancy, Louis D. “Skip” Nichamin, MD, OSN Cataract Surgery Board Member, told OSN. Currently, the only accommodating IOL approved by the U.S. Food and Drug Administration is the Crystalens (Bausch & Lomb).

Louis D. Nichamin

“I believe that multifocals are wonderful. They’ve improved markedly in recent years, but they’re limited, and they will always be limited. I believe that a true shape-changing lens will be our ultimate goal,” Dr. Nichamin said.

Ideally, an accommodating IOL would offer “seamless” accommodation of 8 D or 9 D and emulate the eye’s natural crystalline lens, he said.

Jay S. Pepose, MD, PhD, told OSN that accommodating IOLs will gain prominence as patients continue to live longer and face diminished contrast sensitivity.

“I think that the way of the future is going to be accommodating lenses because you’re not giving up contrast sensitivity,” Dr. Pepose said.

He also envisioned lenses combining accommodation and astigmatism correction.

“I’m sure we’re going to see more torics,” he said. “I think all of the companies realize that there’s a certain lack of predictability in terms of wound healing with limbal relaxing incisions, and it creates more dryness. I think we’ll see more toric aspheric monofocals. We’ll see toric multifocals. And we’ll see toric accommodating lenses.”

Jay S. Pepose

Ideally, Dr. Nichamin said, both lower- and higher-order aberrations should be corrected through a pseudophakic means; however, the need to correct astigmatism or higher-order ocular aberrations is secondary to the need to mimic natural accommodation without diminishing quality of vision.

“We can always address astigmatism on the cornea or with additional lenticular technology, but the Holy Grail, as I see it, is having the ability to provide true accommodative amplitude through a lens without degrading the quality of vision, as we unfortunately do with multifocals,” Dr. Nichamin said.

Crystalens HD and Synchrony

The Crystalens HD was designed to improve near vision without diminishing intermediate or distance vision, Dr. Pepose said.

“They modified the 5-[mm optic], in that the central 1.5 mm of the optic has a reduced radius of curvature,” he said. “They’ve done what would be called a bispheric modification of the lens. That increases the depth of field and increases near and intermediate vision. … Without sacrificing distance vision or without sacrificing contrast sensitivity, they enhanced the near outcomes with the lens.”

The Synchrony dual-optic accommodating lens (Visiogen) is the first three-dimensional lens using anterior and posterior optics to fill the capsular bag, said Dr. Chu, who is an investigator in FDA clinical trials of the Synchrony lens.

“I think our anecdotal results have been excellent with that lens, and I think it’s something to look forward to when it gets FDA approval,” Dr. Chu said.

Light Adjustable Lens

The Light Adjustable Lens (LAL, Calhoun Vision) is another step forward in accommodating IOL technology, Dr. Pepose said.

The LAL is composed of photosensitive silicone macromers embedded in a high molecular weight matrix. Lens power can be precisely adjusted to address residual spherical errors of up to 2 D and correct up to 2 D of astigmatism by irradiating the lens with low-intensity ultraviolet light. The photopolymerization of the macromers forms an interpenetrating network. The unreacted macromer from non-UV exposed areas then physically migrates into the polymerized zone, re-establishing chemical equilibrium and thereby altering lens curvature and thickness.

“Instead of having to do a laser vision correction or even an IOL exchange, this allows an adjustment of the power of the lens by light postoperatively, once it’s in the eye,” Dr. Pepose said. “I think that’s an interesting technology. It could be licensed to existing lenses.”

Dr. Pepose is an investigator in an ongoing phase 2 clinical trial for the LAL, which is approved for clinical use in the European Union.

Dr. Chu said the LAL is a noninvasive alternative to laser refractive enhancement surgery.

“The ability to customize an implant once it’s in a patient’s eye is very attractive,” he said. “Not every surgeon has access to an excimer laser. Potentially, this kind of technology allows us to maximize patients’ visual outcomes with a very noninvasive technique.”

FluidVision lens

The FluidVision accommodating IOL (PowerVision) uses fluid-driven mechanics to alter the curvature of the anterior optic, creating visually significant accommodative power, according to PowerVision literature.

The altered curvature of the anterior optic mimics natural accommodation in the capsular bag and crystalline lens, Dr. Chu said.

“We change the shape of our lens as opposed to moving the lens,” he said. So these lenses are approaching a more natural way of achieving accommodation.”

Dr. Nichamin, who has been working with PowerVision on the FluidVision lens since its inception, said early testing in nonsighted eyes has yielded promising results.

“That’s the type of technology that I think will ultimately change the entire playing field,” Dr. Nichamin said. “Currently, the lens is in nonsighted eyes, and based on pharmacologic stimulation, it’s showing the potential for significant accommodation.”

Pharmacologic stimulation has produced some accommodative response in a set of five glaucomatous eyes. – by Matt Hasson

Click here to see the Guide to IOLs.

• Y. Ralph Chu, MD, can be reached at Chu Vision Institute, 9117 Lyndale Ave. S., Bloomington, MN 55420; 952-835-0965; fax: 952-835-1092; e-mail: yrchu@chuvision.com. Dr. Chu is a consultant to Bausch & Lomb and Visiogen.
• Louis D. “Skip” Nichamin, MD, can be reached at Laurel Eye Clinic, 50 Waterford Pike, Brookville, PA 15825; 814-849-8344; fax: 814-849-7130; e-mail: nichamin@laureleye.com. Dr. Nichamin is a scientific adviser for PowerVision.
• Jay S. Pepose, MD, PhD, can be reached at Pepose Vision Institute, 16216 Baxter Road, Suite 205, Chesterfield, MO 63017; 636-728-0111; fax: 636-728-0287; e-mail: jpepose@peposevision.com. Dr. Pepose is a consultant to Bausch & Lomb and Visiogen.