Stability and Predictability of the Crystalens

Sharing experiences with patients over 7 years.

By James A. Davies, MD, FACS

Since first implanting the Crystalens AT45 shortly after FDA approval in 2003, I have found the original Crystalens model and each subsequent version to give predictable and stable surgical results. The vast majority of our patients are very pleased with their visual outcome with very few exceptions, and those exceptions are typically due to an unexpected refractive result or to residual uncorrected corneal astigmatism.

Obtaining Optimal Results

Factors crucial to obtaining an optimal result include treating dry eye, accurate biometry and careful attention to surgical detail, including an absolutely watertight incision to prevent anterior displacement of the optic. It is also essential to treat astigmatism, as residual cylinder can adversely impact vision in premium IOLs. This is addressed with corneal relaxing incisions at the time of the procedure, and PRK or LASIK after the fact as needed. My personal preference is to operate first on the non-dominant eye. The refraction tends to be quite stable at the 2-week postoperative visit, with very little change noted between 2 weeks and 3 months.

If, for example, the patient is 0.4D more myopic than expected, this is likely due to the fact that the IOL optic is slightly more anterior than anticipated. By performing surgery consistently, the refractive result probably will be the same in the fellow eye (0.4D more myopic than originally targeted), so selecting an IOL power to compensate for this deviation from target observed in the first eye has given very predictable results. The ability to select IOL powers in .25D increments (currently from 18D to 22D with the Crystalens AO) gives greater precision in our results. This precision allows us to provide better refractive outcomes across a broader patient population.

Remarkable Results

Surgical results of each of the premium IOL platforms have been tracked by Guy M. Kezirian, MD, in his Surgivision DataLink program. The Crystalens model has demonstrated predictable and stable results that are comparable to those achieved by the earlier AT-45 and Crystalens Five-O models. My results over seven months with the Crystalens AO have been comparable to the results seen with both the 5-0 and HD models. The Crystalens AO has been delivering excellent functional vision across all of the viewing distances. More than 95% of our bilateral Crystalens patients are able to meet Department of Motor Vehicle requirements, see their computer and read the newspaper without spectacle correction. All Crystalens models are highly predictable in terms of achieving the desired postoperative refractive target, similar to the other presbyopic lenses. Analysis from the SurgiVision database (Figures 1 and 2) shows the mean post-op spherical equivalent at 1 month for the Five-O, the HD, the ReSTOR* 3D and 4D aspheric (Alcon) and the Tecnis* Multifocal (AMO). The means are a function of the recommended targeting for each lens. The standard deviations are very similar. The differences between the values are not statistically significant. Thus, the refractive predictability of the lenses is essentially the same.

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Figures 1 and 2. The standard deviations are very similar across each platform. The differences between the values are not statistically significant. Thus, the refractive predictability of the four lenses is essentially the same. Results are taken from the B&L SurgiVision® DataLink IOL Registry, administered by SurgiVision Consultants, Inc. of Scottsdale, Arizona.

Crystalens AT-45 Study Summary

John Doane, MD, and Michael Colvard, MD, conducted the Crystalens AT-45 retrospective study, which analyzed 33 patients (60 eyes) and has the longest follow-up to date on an accommodative IOL. There is no comparable study approaching this duration with any of the multifocal IOLs. Patients were recalled at 3 and 7 years post-op for assessment of monocular and binocular corrected and uncorrected distance, intermediate and near visual acuity.

The study found that the Crystalens AT-45 is able to provide functional near, intermediate and distance vision over an extended follow-up period (Figures 3-5; Bausch + Lomb, Data on file, FDA Clinical Trials). In addition, the study showed no evidence of the effectiveness of the lens being minimized by changes to the capsular bag. YAG laser capsulotomy had no statistically significant impact on accommodation. Lastly, at seven years 100% of patients were 20/32 or better at distance and intermediate and 88% were 20/32 or better at near.

Figure 3. When measuring binocular uncorrected intermediate visual acuity at 1 year, 65% of patients were 20/25 or better, with 100% at 20/32 or better. At 7 years, 96% were 20/25 or better and 100% were 20/32 or better.

Figure 4. When measuring binocular uncorrected near visual acuity at 1 year, 13% of patients were 20/20 or better, 79% were 20/25 or better, 96% 20/32 or better and 100% 20/40 or better (N=24). At 7 years, 16% were ≤20/20, 60% were 20/25 or better, 88% 20/32 or better and 96% 20/40 or better (N=25).

Figure 5. When measuring binocular best-corrected distance visual acuity at 1 year, 92% of patients were 20/20 or better; at 3 years, 86% were 20/20 or better; and at 7 years, 88% were 20/20 or beteter.

My earliest patients implanted with the Crystalens AT45 during the years between 2003 to 2006 have stable refractive results and remain very pleased with their quality of vision and freedom from eyeglasses. My experience shows that over time, most patients have stable distance acuity with improvement of near and intermediate uncorrected vision.

I've noted a similar trend in patients implanted with the Crystalens 5-0 and HD lenses from 2006 to 2010. Whether this is due to neuroadaptation or increased accommodative amplitude, or a combination of both, the bottom line is that patients are very happy with the results — they're our greatest cheerleaders.

Crystalens AO 3-Month Data Findings

Twenty-three surgeons participated in a pre-release evaluation of the Crystalens AO with 836 eyes reviewed at 1 month post-op and 199 at 3 months postop. The results of the Crystalens AO 3-month data were examined two ways. First, all of the eyes have been entered on Datalink with no filters applied, and second, eyes with what were termed "plano" outcomes were used. These eyes had post-op outcomes that were within +/− 0.50 of plano and had less than 1.50D of astigmatism postoperatively. This particular cylinder amount was selected because it is the cutoff that is given to new surgeon for their first 6 cases. Refractive predictability was evaluated using the entire data set (no filters). In order for eyes to be included in this analysis, there had to be a pre-op target and a post-op refraction entered in Datalink. Refractive stability was examined using the entire data set as well. In order to be included in this analysis, it was required that the eye have a 6- to 18-day refraction and a 3-month refraction entered in Datalink. Predictability is very good with 93% of eyes within +/− 0.75 D of intended target. This will likely improve with the recent introduction of 0.25D steps with the AO. Refractive stability between 2 weeks vs. 3 months shows that refractions are stable over time with most eyes changing less than 0.50D over that time period. This also demonstrates that our a-constant and formulae appear to be correct. The large majority of outcomes were within 0.25D to 0.50D of the intended target. Visual acuity and post-op refraction are stable over time. We found no significant change in distance acuity, with a slight improvement in uncorrected intermediate and near acuity. Even with a plano result, the uncorrected near acuity is quite good. Only minimal refractive drift was noted over time. This study showed that refractive predictability of the Crystalens AO is excellent.

Personal Experience With the Crystalens

My own clinical experience over the past 7 years with all Crystalens platforms (AT-45, 5-0, HD, and the AO) has shown that with time and practice, i.e. reading exercises and normal day-to-day visual tasks, near and intermediate acuity show a gradual but steady improvement with the vast majority of my patients able to watch TV, drive, use the computer and read without eyeglasses. Complaints of halos and glare are virtually nonexistent.

My results over 7 months with the Crystalens AO have been comparable to the results seen with the 5-0 and HD models, and predictability is in line with the SurgiVision Datalink summary. It is proving to be an excellent lens in terms of stability and predicted outcomes.

With 7 years of Crystalens experience, I have an army of happy patients openly sharing their results with anyone who will listen. Not only has this remarkable lens implant dramatically increased the enjoyment of my surgical practice, but it has done wonders for the bottom line of the practice — many patients are coming to us specifically requesting the Crystalens, a reliably stable and predictable lens.

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Dr. Davies is Medical Director of Davies Eye Center and The Surgical Eye Care Center, Carlsbad, Calif. He can be reached at jdaviesmd@davieseye.com.