Long-term Stability of Accommodative IOLs

Seven years after implantation, IOLs retain good near, intermediate and distance vision.

By D. Michael Colvard, MD, FACS

Although we're accustomed to achieving excellent results with accommodative IOLs, until recently, little was known about the performance of these IOLs over the years. Now, retrospective data are beginning to give us a clearer picture of how accommodative IOLs perform long term. A sample of patients, who received the first accommodative IOL, the Crystalens AT-45, during FDA trials performed 7 years ago, shows that this lens is effective and stable over time. Retrospective analysis has demonstrated that patients enrolled in the FDA premarket evaluation have maintained good near, intermediate and distance uncorrected binocular vision 7 years after surgery.

Looking Back

Since Crystalens (Bausch + Lomb) was introduced as the first presbyopia-correcting IOL in 2003, its original and evolving forms have been implanted in more than 200,000 eyes.¹ Initial results of the FDA trial for the first iteration of Crystalens, the AT-45, demonstrated that the lens had an accommodative effect as intended.² It was approved by the FDA, and although the design has been enhanced over the years, Crystalens is still the only accommodative IOL on the market.

It's been our hope that patients with these lenses would continue to have good vision for the rest of their lives, but because accommodative IOLs are a relatively new technology, we have known little about the long-term stability of their accommodative effect. Data showed that patients who received the Crystalens AT-45 had good uncorrected and corrected near, intermediate and distance vision 1 year after surgery.² Yet the question remained, what would happen to the accommodative capability as the capsule became fibrotic, the posterior capsule became opaque, or even when unforeseen events occurred?

To learn more about how patients who receive the lens experience changes in vision over time, I co-authored a retrospective study of follow-up data for patients from the Crystalens AT-45 FDA trial. John F. Doane, MD, and I oversaw two original study sites for the Crystalens AT-45. That study included the immediate surgical results, as well as 1-year follow-up data. We both saw our patients again at 3 years and 7 years (a total of 33 out of 51 patients, or 60 eyes). We compared the 3-year and 7-year visual acuities to the 1-year results for best-corrected and uncorrected near, intermediate and distance vision. Of the 33 patients, 27 underwent bilateral implantation and 6 underwent unilateral implantation, so we evaluated both monocular and binocular visual acuity.

Enrollment criteria for the original study meant that the group was in good ocular health. Patients had to be over 50 years old with no ocular pathology and no more than 1 D of corneal astigmatism. They had to have the potential for 20/32 or better best-corrected distance vision. The procedure was standard phacoemulsification and capsular bag IOL implantation.

In follow-up exams, we tested near vision at 16 inches and intermediate vision at 32 inches. We followed the FDA study procedure of testing near and intermediate visions through distance correction to minimize the confounding effects of residual refractive errors, including astigmatism and myopia.

Long-term Data

The long-term follow-up data on accommodative IOLs showed excellent efficacy and stability over the years, as well as some unexpected results.

The numbers show that stability of the Crystalens AT-45 was excellent over 7 years, with very little change in near or distance vision (Figures 1-3). However, the change in intermediate vision was dramatic—a leap from 65% of patients at 20/25 or better to 96% of patients at 20/25 or better. One might hypothesize that this improvement in uncorrected intermediate vision is due to strengthening of accommodation associated with increased activity of the ciliary body after Crystalens implantation, but confirmation of this observation through additional study is needed to establish the validity of this finding.

Interpreting the Results

Clearly, the study shows there was no drop-off in accommodative effect over time. The fairly young age of this cohort explains why there was no drop-off related to age-related macular degeneration or other age-related pathology. Patients selected for the FDA clinical trial were required to have a potential of a 20/20 result. Patients with ocular pathology that might reduce the outcome are typically excluded from trials. The greatest vision risk for most cataract patients is development of AMD, which reduces vision at all levels over time. We currently do not have long-term studies of IOL patients who develop AMD or other common age-related problems.

In the general population of patients receiving cataract surgery, we could expect to see the effects of disease, although patients receiving the Crystalens IOL do not represent a cross section of cataract patients.

When I choose a candidate for the Crystalens, my ocular health criteria are similar to those in the FDA trial. In general, I only implant premium IOLs in patients with very good macular function. The key issue for my patients is good visual potential. I want them to appreciate the benefits of the technology, and other pathologies, such as significant epiretinal membrane or severe glaucoma, would keep patients from seeing the full potential of Crystalens.

Patients with significant AMD will not have excellent reading vision regardless of how the lens performs, so I don't use Crystalens for these patients. However, patients with very mild AMD are often good candidates. There is an advantage over multifocal lenses in that Crystalens doesn't reduce visual quality or contrast sensitivity in patients who have already lost contrast sensitivity because of AMD.

In my cohort, at 7 years, 87% of the study patients had undergone YAG capsulotomy, but the data showed that these patients had good near, intermediate and distance vision as well. I found no evidence that the Crystalens AT-45's efficacy declined due to capsular bag contraction or YAG capsulotomy.

One final point to note is that when Crystalens was in clinical trials, we were implanting the lens without an inserter through a 3.5-mm incision. The unique design of Crystalens, with its stabilization haptics at right angles, made it difficult to design an inserter. However, soon after the lens was approved, the challenge was surmounted and the Crystalens inserter was released, allowing us to implant this foldable lens more easily with a smaller 2.5-mm incision. All of the patients in this study had the 3.5-mm incision without the inserter, not the procedure peformed today with the inserter.

Nevertheless, the results were reassuring. Clearly, in this longest follow-up study to date of an accommodative IOL, the Crystalens AT-45 was shown to provide accommodative vision at 7 years comparable to the results at 1 year.

REFERENCES

1. Bausch & Lomb data on file. (http://www.crystalens.com/us/IsCrystalensRight-ForYou.aspx).
2. Cumming JS. Colvard DM, Dell SJ, Doane J, Fine IH, Hoffman RS, Packer M, Slade SG. Clinical evaluation of the Crystalens AT-45 accommodating intraocular lens. J Cataract Refract Surg 2006; 32:812-825.

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Dr. Colvard is the Director of Colvard Eye Center in Encino, Calif. He is a Clinical Professor of Ophthalmology at the Keck School of Medicine, University of Southern California, and the editor and a principal contributor to the textbook Achieving Excellence in Cataract Surgery.