EyeWorld Asia-Pacific June 2012 Issue

21 EWAP CATARACT/IOL June 2012 The NuLens accommodating IOL Source: I. Howard Fine, MD The FluidVision IOL Source: PowerVision The Tetraflex lens Source: Paul J. Dougherty, MD pushes the base unit up into the top unit and actually changes the radius of curvature and power.” This lens’s accommodative mechanism is opposite that of The Synchrony dual-optic lens Source: Abbott Medical Optics patients so far and has attained between 4-7 D of accommodation, according to Dr. Slade, who is the trial surgeon. “We are hoping to begin FDA trials this year,” Dr. Slade said. “At this current time we have not gotten the CE mark.” Dual personality Also with two components, the Synchrony dual-optic lens (Abbott Medical Optics, AMO, Santa Ana, Calif., USA) is the only other lens besides the NuLens that has been documented to move, according to Mark Packer, MD , clinical associate professor of ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, Ore., USA. Specifically, it is the anterior component that moves. “When we try and focus up close, the ciliary muscle contracts, releasing tension on the zonular fibers; the spring that is inside the structure of the Synchrony actually has memory,” Dr. Packer said. “Then when the Robert ANG, MD Cornea and Refractive Surgeon, Asian Eye Institute 8th Floor Phinma Plaza, Rockwell Center, Makati City, Philippines Tel. no. +632-8982020 Fax no. +632-8982002 RTAng@asianeyeinstitute.com A ccommodating IOLs allow simultaneous correction of refractive error and presbyopia during cataract surgery. This is done either through axial movement of the lens or wavefront changes over the optic. Accommodating IOLs have to compete with multifocal IOLs which work via the splitting of light. The Crystalens is the first U.S. FDA-approved accommodating IOL in the market. We conducted a prospective study comparing the Crystalens AO with the ReSTOR +3 (Alcon, Fort Worth, Texas, USA/Hünenberg, Switzerland) and Tecnis Multifocal lens (AMO) and found several interesting conclusions (unpublished data). First, uncorrected distance vision is similarly good with the three lenses but intermediate vision is better with the Crystalens whereas near vision is better with the two multifocal lenses. Second, quality of vision metrics such as low contrast vision, contrast sensitivity and unwanted visual phenomena such as haloes and starburst are significantly worse in the two multifocal lenses compared to the Crystalens. Third, over time, as the capsule fibroses and contracts, the Crystalens can have some changes in vaulting and tilt which can affect vision and refraction whereas in the multifocals, posterior capsule opacification also occurs but the effect is not on lens position but on worsening contrast. YAG capsulotomy will eventually be performed but the timing and indications may differ for the three lenses. Having the Crystalens in the market has opened our eyes that not all patients can be happy with multifocal lenses even though they provide the best uncorrected near vision. There is always a trade-off and proper patient selection is necessary. It has also stimulated research into better ways of improving pseudophakic accommodation restoration. For a new accommodating lens to flourish, it has to match the good quality of vision, provide better near vision, be easy to use and be less susceptible to capsular contraction compared to the Crystalens. Among the new accommodating lenses, the Tetraflex seems to be the most similar to the Crystalens wherein both are single-optic lenses with the presbyopia-correcting power mostly attributed to higher-order aberration changes and less likely attributed to lens movement. Being single optic has the advantage of easier implantation and handling but the similar disadvantage of minimal lens movement and susceptibility to capsule contraction. The NuLens and Synchrony are both dual-optic lenses wherein a robust range of vision is provided by moving one optic towards and away from the second optic. The Synchrony seems like a huge lens and implanting it may require a larger corneal incision and sutures which can induce postoperative astigmatism. Inflammation control after surgery will be very important because unwanted fibrosis may form in- between the two optics. What would be interesting is how the optics would behave if and when a YAG capsulotomy is done in the future. The FluidVision lens is the most revolutionary concept wherein accommodation is provided by fluid transmission to the central optic causing increased curvature and accommodative power. Centration will be very critical and the material has to be biocompatible. We look forward to seeing the visual performance and long-term outcomes of these new accommodating lenses as they gradually enter the market. Editors’ note: Dr. Ang is on the speakers’ boards and given lectures for AcuFocus (Irvine, Calif., USA), Allergan (Irvine, Calif., USA), Bausch + Lomb, and Technolas Perfect Vision (Munich, Germany). Mother Nature, according to Douglas D. Koch, MD , professor and the Allen, Mosbacher, and Law Chair in ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. He pointed out that in typical accommodation when the ciliary body contracts, it relaxes the zonules, causing the lens to move forward slightly, but more importantly assuring a more spherical shape and an increase in power. The NuLens, however, is different. “This is relying directly on the force of the ciliary body and is not relying on any effect of the capsule, except as tension is created on it as the ciliary muscle relaxes,” he said. “It’s probably a more direct transmission of ciliary muscle energy to the implant.” He finds that some neuroadaptation is required with the lens because accommodation occurs as the ciliary muscle relaxes, not as it contracts. Despite this unusual mechanism Dr. Koch sees the lens as promising. “So far every challenge they have placed on this theory has passed with flying colors,” he said. The lens has been tested in 30 continued on page 24