Innovative IOL breaks new ground in presbyopia-correcting implant technology

October 15, 2014

A new presbyopia-correcting IOL has a novel optic combining two complementary diffractive technologies. Results from bench and clinical testing show it provides a full range of continuous, high-quality vision, minimizes dysphotopsias, and may be more tolerant to refractive errors than multifocal IOLs.

 

TAKE HOME:
A new presbyopia-correcting IOL has a novel optic combining two complementary diffractive technologies. Results from bench and clinical testing show it provides a full range of continuous, high-quality vision, minimizes dysphotopsias, and may be more tolerant to refractive errors than multifocal IOLs.

 

Dr. Auffarth

By Cheryl Guttman Krader; Reviewed by Gerd U. Auffarth, MD

Findings from studies evaluating the performance of a new presbyopia-correcting IOL (Model ZXR00; Tecnis Symfony Extended Range of Vision IOL, Abbott Medical Optics) indicate that it provides a full range of continuous, high-quality vision and successfully addresses the limitations accompanying multifocal IOL technology.

The novel IOL possesses innovative surface design features that result in 50% less light loss than traditional diffractive technologies such as multifocal or trifocal IOLs, enhanced depth of focus, crisp image quality, and very low rates of visual symptoms. The Symfony Extended Range of Vision IOL has received the CE Mark, is available in Europe, and is being studied in a pivotal trial in the United States.

 

“Recent strategies for enhancing multifocal IOL technology have focused on ways to improve intermediate vision, and this has been accomplished with the introduction of trifocal designs and lenses with a lower add. However, because a multifocal optic distributes light to different foci, all multifocal IOLs suffer from problems with contrast sensitivity loss and dysphotopsias,” said Gerd U. Auffarth, MD, professor and chairman, department of ophthalmology, Ruprecht-Karls University of Heidelberg, Germany.

“This extended range of vision IOL represents an entirely new design concept that allows for an extended range of crisp vision and a high rate of spectacle independence while minimizing photic issues, such as halos and glare, to levels similar to those occurring with a monofocal IOL,” he said

Discussing the design of the new lens, Leonard Borrmann, PharmD, divisional vice president, research and development, Abbott Medical Optics, Santa Ana, CA, explained it combines two complementary diffractive technologies. The first technology uses a modification of the height and the profile of the diffractive echelette to elongate the focus, as compared with the diffractive echelletes in a multifocal that create two discrete foci.

“Typically, optics that create multiple foci or that elongate the focus suffer from some loss of image quality,” Dr. Borrmann said. “However, the Symfony IOL optic compensates for that problem by incorporating a second diffractive optic technology that reduces chromatic aberration and boosts image quality.”

 

The optics in a refractive system, including cameras, telescopes and the eye itself, all have some degree of chromatic aberration such that the focal point varies for different wavelengths of light. For example, whereas green light focuses on the retina, the focal point is anterior to the retina for blue light and falls behind the retina for red light. Chromatic aberration causes blur that can degrade image quality and contrast, explained Patricia Piers, PhD, director of IOL research and development, Abbott Medical Optics.

“The achromatic technology in the Symfony IOL corrects for the positive natural chromatic aberration of the eye by providing negative chromatic aberration just as a negative aspheric IOL design compensates for positive spherical aberration in the average cornea,” Dr. Piers said.

“By correcting for the eye’s positive chromatic aberration, achromatic technology enhances contrast,” Dr. Piers said. “And, in combination with its aspheric optic profile, the Tecnis Symfony IOL delivers high image quality without any effect on range of vision.”

Proof of performance

An initial prospective clinical study conducted in New Zealand compared the new extended range of vision IOL with the single-piece Tecnis monofocal IOL (ZCB00, Abbott Medical Optics). In that trial, 31 patients were bilaterally implanted with the new IOL and there were 10 implanted patients that received bilateral monofocal IOLs.

The results showed that binocular far UCVA was similarly excellent in the two groups. However, patients receiving the extended range of vision IOL had significantly better distance-corrected intermediate (66 cm) and near (40 cm) visual acuity.

In addition, 96% of patients in the extended range of vision IOL group achieved 20/25 or better intermediate UCVA compared with only 74% of controls, while 92% of patients in the new IOL group and 42% of the controls had near UCVA of 20/40 or better.

The binocular defocus curve showed the new lens was associated with a statistically and clinically significant increase in depth of focus compared to the monofocal IOL. Patients implanted with the extended range of vision IOL had sustained mean VA of 20/20 or better through 1.5 D of defocus and a full range of functional vision (ie., 20/40 or better) through 2.5 of defocus.

At the XXXII Congress of the ESCRS in London, Dr. Auffarth reported outcomes from an ongoing open-label prospective, multicenter trial investigating the extended range of vision IOL. The study has a planned enrollment of 150 patients, and as of mid-September, 2014, all 150 participants had been enrolled at 14 clinical sites across Europe.

The results presented by Dr. Auffarth were from 82 bilaterally implanted patients with 1-month follow-up. For the group, mean logMAR UCVA was -0.01 for far, 0.03 for intermediate, 0.18 for near (measured at 40 cm), and 0.07 for near at the patient’s best distance, which was about 47 cm. The mean minimum near add for best near VA at 40 cm was 1.2 D.

 

 

 

Overall, more than 90% of patients achieved binocular UCVA of 20/25 or better for both far and intermediate, 99% had binocular UCVA of 20/40 or better at far and intermediate, and 88% of patients were seeing at least 20/40 uncorrected at near.

Defocus curve testing highlighted the extended range of vision provided by the lens, with a sustained mean visual acuity of 20/32 or better through more than 2.0 D of defocus and of 20/40 or better through 2.5 D of defocus.

“The defocus curve established in clinical testing for this new lens is consistent with that predicted from bench data and stands in contrast to the defocus curves of traditional multifocal IOLs that feature two distinct peaks,” Dr. Auffarth said.

“From this testing it is quite clear that the new lens provides ample uncorrected distance and intermediate visual acuity,” Dr. Auffarth said.

Benefit of micromonovision approach

He noted that based on analyses of UCVA data from patients with a small interocular difference in postoperative refraction, it appears that a micromonovision approach may enhance near functional outcomes with the new lens. Patients with a refractive error ≤-0.5 D in one eye and within ±0.5 D in the fellow eye had a mean near UCVA of 20/32 and maintained excellent intermediate and far UCVA.

About 97% of patients said they were able to function comfortably without glasses for distance and intermediate vision tasks and almost three-fourths were spectacle independent for near.  All but two patients said they would recommend the lens to friends and family.

Other subjective data showed the lens design met its objective for minimizing the visual disturbances associated with multifocal IOLs. Ninety-three percent of patients reported no day glare and 98% experienced no night glare. In addition, about 90% of patients reporting experiencing no halos or starburst, and when they occurred, these symptoms were rarely severe.

These findings are consistent with data from the study in New Zealand in which the incidence and degree of difficulty with halos and glare was similar in the extended range of vision IOL and monofocal IOL control groups.

“These results are very encouraging in suggesting this new lens will successfully mitigate the adverse effects associated with multifocal IOL technology,” Dr. Auffarth said.

 

Tolerance to refractive error

Another benefit of the new IOL is that it appears to be more tolerant than multifocal IOLs to refractive errors, both sphere and cylinder. This feature was investigated through testing in the optics laboratory of Pablo Artal, PhD, at the University of Murcia, Spain using adaptive optics vision simulation technology.

As reported by Dr. Piers at the ESCRS Congress, the study included 5 subjects and used a binocular adaptive optics vision simulator to assess high contrast visual acuity as a function of object vergeance with SLOAN letters. The testing was done with a pupil size of 3.5 mm in white light and under monocular conditions with the subjects looking through a phase profile corresponding to the Tecnis Symfony IOL design.

The results showed that distance corrected visual acuity stayed within 1 line of peak performance over the range of vergeances from –0.5 to 1.5 D. The shape of the defocus curve was not affected by refractive errors, but rather only its position was shifted to the left or right, she reported.

“These data indicate that errors in IOL power selection of plus or minus 0.5 D at the spectacle plane will still allow for excellent distance and intermediate uncorrected visual acuity,” Dr. Piers said.

“Similarly, the shape of the defocus curve was unaffected by the presence of residual astigmatism of up to 1 D, and this residual astigmatism does not significantly affect the range of object distances over which visual acuity remained within 1 line of peak performance.”

 

Gerd U. Auffarth, MD

Dr. Auffarth is a consultant to Abbott Medical Optics and other companies that market IOLs and has received research and travel grants, lecture honoraria, and funds for research from Abbott Medical Optics and from other companies marketing IOLs.