IOL delivers on visual quality, acuity
Dr Doane reviewed results from studies comparing the lens, an accommodating IOL featuring a monofocal optic with aspheric (spherical aberration neutral) anterior and posterior surfaces, against refractive and diffractive multifocal implants.
The data showed that when compared against various multifocal IOLs, the accommodating IOL delivered superior optical performance, as measured by image quality and modulation transfer function (MTF), better distance and intermediate uncorrected visual acuity (UCVA) outcomes, and comparable functional near UCVA.
"Image quality is extremely important for patient satisfaction," said Dr Doane, a refractive and corneal surgeon and clinical assistant professor of ophthalmology, Kansas University Medical Centre, Kansas City, USA. "While multifocal IOLs can provide a full range of functional vision effectively, one cannot ignore the fact that splitting of light by a multifocal optic introduces trade-offs, including visual side effects and reduced quality of vision.
"While we can explain these consequences to patients and hope they understand the risks, in the absence of any technique for preoperatively assessing patient tolerability, whether patients notice these adverse phenomena, can tolerate the side effects, or will neuroadapt relatively quickly are unknowns," he said. "Certainly, there is individual variation with respect to these issues, and surgeons must be aware that there are some patients who can take years to adjust or never neuroadapt."
In one laboratory study, distance imaging quality associated with the accommodating IOL and two diffractive multifocal IOLs (AcrySof ReSTOR +3.0 D, Alcon Laboratories and Tecnis, AMO) was simulated objectively using a commercially available optical design programme. At a 3-mm pupil size, the accommodating lens delivered superior distance image quality compared with both of the diffractive multifocal IOLs.
Consistent with these findings, computation of MTFs for six different marketed presbyopic IOLs [Crystalens AO, Crystalens 5-0, Crystalens HD (all Bausch + Lomb); AcrySof ReSTOR +4.0 D, AcrySof IQ ReSTOR +3.0 D (Alcon Laboratories); and ReZoom multifocal IOL (AMO)] showed that with a 3-mm aperture, the Crystalens AO curve was closest to ideal.
Distance, intermediate vision outcomes
Comparisons between the Crystalens AO and the Tecnis and AcrySof ReSTOR +3.0 D diffractive multifocal IOLs showed the accommodating implant performed better than the multifocal technology with respect to distance and intermediate vision outcomes.
"With binocular testing, near, intermediate and distance UCVA were all 20/25 or better in at least 97% of patients with the Crystalens AO implanted bilaterally," Dr Doane said.
The data on monocular UCVA were based on follow-up at 3 months after surgery with no enhancements. Among 91 eyes with the accommodating lens implanted, about two-thirds achieved 20/25 or better distance UCVA and 40% achieved 20/20 or better. Only about half of eyes with the Tecnis or ReSTOR multifocal IOLs implanted achieved distance UCVA of 20/25 or better, and just more than 20% of eyes in these implant groups achieved 20/20 or better.
"The benefit of the Crystalens AO occurred despite the fact that the multifocal IOL groups had a less myopic mean outcome for spherical equivalent," Dr Doane said.
"In a study where I mixed the ReSTOR +4.0 D and Crystalens 5-0 in fellow eyes, I found distance best-corrected visual acuity was better by about 1 line in eyes with the accommodating IOL," he added. "This difference is not unexpected considering that visual function is likely to be better if you hit the refractive target with an IOL that has a monofocal optic compared with a diffractive design."
In monocular testing of intermediate vision, 77% of the eyes with the accommodating lens achieved 20/20 or better UCVA and 95% could see 20/25 or better. The ReSTOR multifocal IOL offered the next best performance, but only 64% of eyes with that lens implanted achieved 20/25 or better intermediate UCVA and only 38% could see 20/20 or better.
"Intermediate UCVA is where the accommodating IOL really shines, since multifocal IOLs do not have a focal point for intermediate," he said.
"However, because the diffractive multifocal IOLs provide a very high add for near function at a specific reading distance, they have a benefit for providing better near vision."
Data on monocular near UCVA showed rates of J1 vision were about two-fold higher for the ReSTOR and Tecnis multifocal IOLs compared with the Crystalens AO (~70% versus 35%, respectively). However, 71% of patients with the accommodating lens implanted could read J2 or better, and all three IOLs were associated with rates of J3 or better near vision that were similarly high, >90%.