Trulign by the Numbers
The Trulign, like the standard Crystalens, is a silicone lens with a 5-mm optic and flexible, rectangular hinged haptics with polyamide loops. It’s available in +4 to +10 D spherical equivalent powers (in 1-D increments) and +10.5 to +33 D powers (in 0.5-D increments). It was approved for three cylinder powers: 1.25; 2.00 and 2.75 D, measured at the IOL plane. “This range of astigmatic correction covers roughly 90 percent of patients who can benefit from astigmatism correction,” says Encino, Calif., surgeon and Trulign investigator Michael Colvard. “Eyes with higher cylinders are far less common. Patients with higher levels of astigmatism who are without corneal pathology such as keratoconus, in my experience, can have their correction augmented with peripheral corneal incisions.”
In the Trulign FDA study of 210 subjects, 79.9 percent of the 1.25-D toric cohort achieved the intended reduction in cylinder vs. 46.5 percent of non-toric controls (p<0.001). The mean percentage reduction of cylinder for the 2-D toric cohort was 88 percent, for the 2.75-D cohort it was 97 percent and for all torics it was 85 percent.
Ninety-six percent of implants rotated 5 degrees or less between the day of surgery and three to six months postop.1 “I think the key to that is the polyamide loops,” explains Jay Pepose, MD, medical monitor for the Trulign FDA study. “They seem integral to the rotational stability of the lens.”
In 147 patients studied for safety at three to six months in the FDA study, one patient had macular edema (0.7 percent) and one needed a secondary surgery to reposition the IOL, but this repositioning wasn’t related to axis misalignment or rotation. One patient experienced a significant visual disturbance, while 99 percent had none. Dr. Pepose says this is a boon for older patients. “I explain to them that one advantage to the lens is they’re not going to be at increased risk for glare, halo or reduced contrast sensitivity,” he says. “Patients are living longer and longer—it’s not uncommon for us to have patients in their 90s coming in to see us—and we don’t know what’s going to happen to those 75-year-olds as they age. Are they going to get macular degeneration? Epiretinal membrane? Something else that will decrease contrast sensitivity? If I put in a multifocal lens that decreases their contrast and then they live that long, maybe I didn’t do these patients a favor. The accommodative lens might not produce as much near vision as a multifocal, though, so it’s a trade-off.”
Tips and Techniques
Trulign users say they’ve learned some things about implanting the lens that can help get the best outcomes.
• Size the capsulotomy properly. Dr. Colvard says that, like the standard Crystalens, capsulotomy size plays a role in the proper positioning of the lens. “The capsulotomy size is important with the Crystalens,” he says. “You want it to be in the 5- to 6-mm range. It’s my clinical impression that this size gives you more stable refractive outcomes. I believe that a larger capsulorhexis allows the lens to move forward more and produce more of a myopic shift postop.”
Dr. Pepose says a 5.5-mm capsulorhexis seems like a good fit. “We did regression analysis to see if there was an ideal rhexis size to maximize intermediate near vision,” he says. “We found that 5.5 mm seemed to be a good size, just slightly larger than the optic of the lens.”
• Use ORA carefully. If you use Wavetech’s ORA for intraoperative aberrometry with the Trulign, Auburn, Wash., surgeon John Jarstad advises to check and re-check your measurements. “We’ve done about 10 Trulign implantations so far, and they’ve all done really well,” he says. “The one thing we’re still trying to work out though is, in patients with high amounts of astigmatism, we’re not getting complete accuracy in the lens power measurement from the ORA system. As a result, we’re relying more on the IOLMaster-predicted lens power than the ORA in patients with high astigmatism. Hopefully, the new ORA software will work well and we’ll be able to nail down these lens power measurements.”
• Cortical cleanup and lens position. Oakland surgeon Nicholas Batra says this phase of the procedure is important.
• Close the wound tightly. Surgeons agree that, part and parcel with making sure the lens is seated properly is ensuring that the wound is sealed and watertight. “It’s very important to make sure the incision is absolutely secure,” says Dr. Colvard. “If there is any loss of chamber volume postop the lens will tend to vault forward inducing an unplanned myopic shift. With unsutured clear corneal incisions used in conjunction with standard intraocular lenses, a small, transient loss of anterior chamber volume may occur postoperatively but go unnoticed because it doesn’t have much of an effect on the refractive outcome. But if this occurs with Crystalens or Trulign, a loss of chamber volume, even a temporary one, will cause the lens to vault forward and stay there.” Dr. Pepose concurs, saying, “You want the optic in a posterior position with the haptics seated way out in the fornix of the capsular bag, and you want a nice, watertight seal with no leakage, Seidel-negative.”
Going forward, Dr. Pepose says he feels the lens fills a niche that surgeons will appreciate. “In the past, we had monofocal, non-accommodative toric lenses, but this combines the two platforms,” he says. “It’s nice not to have to have patients undergo multiple procedures.” REVIEW
1. FDA Summary of Safety and Effectiveness Data: Trulign. http://www.accessdata.fda.gov/cdrh_docs/pdf3/P030002S027b.pdf. Accessed 24 June 2013.