Spotlight ON TECHNOLOGY & TECHNIQUE

Crystalens HD: A Clear Improvement in Near Vision

By Leslie Goldberg, Associate Editor

Bausch & Lomb's new Crystalens HD (B&L, Rochester, N.Y.) is designed to improve near vision without compromising intermediate or distance vision. Unlike a multifocal, the HD places one point of focus and one image on the retina. The HD lens is designed to provide an enhanced depth of focus.

John F. Doane, M.D., F.A.C.S., is in private practice at Discover Vision Centers in Independence, Mo., and assistant clinical professor at Kansas University Medical Center Department of Ophthalmology, Kansas City, Mo. He has been involved with clinical studies of the Crystalens since 2000.

"It was never intended that the first Crystalens design would be the final design," says Dr. Doane. "From the AT45 design that started the FDA studies to now, there have been three versions. Just like any technology, we keep advancing the field." Dr. Doane traces the development from the AT45 to the AT45 SE (square edge), then the larger diameter optic AT50 SE and variations on the AT50 — like the AT52 for longer eyes.

"One thing that anyone who has an accommodative lens will say is that they want better near vision. That is the concept behind the Crystalens HD. It is about improving near vision. We began these studies in 2006," says Dr. Doane. "We wanted to improve the near function and not decrease the distance and not increase any negative optical affects or dys photopsia secondary to an optical change."

HD Mechanism of Action

The central portion of the optic of the HD lens is slightly thicker than the AT50SE and thus accentuates the accommodative arching effect. The HD is definitely not a multifocal. It places one focal point, hence one image, on the fovea at any one time. The net result is an improvement in near acuity without diminishing distance or intermediate vision or inducing any dysphotopsia or degradation of quality of vision compared to the AT50SE.

Study Findings

Sixty eyes remained in the final study by 6-month follow-up. "We didn't lose anything on the distance acuity," says Dr. Doane. "What we did see was an improvement in the uncorrected near acuity in comparison to the earlier AT45." (See Figure 1)

Figure 1 shows the improvement in uncorrected near acuity of the Crystalens HD.

"The Crystalens HD improves near and intermediate vision without negatively affecting distance or night-time vision. So we didn't lose anything at distance and gained it up close. It delivered that which we wanted," says Dr. Doane.

Dr. Doane explains that distance is relatively stable after 3 months and once that stability is reached, certain refractive enhancements might be needed to get a patient on target. "The near acuity is the only vision that improves time-wise past that point," says Dr. Doane. "I've seen improvement out to 2 years. After that, it's virtually completely stable."

Dr. Doane says that the effective range of near vision with this lens was improved over prior generations and did not result in a loss of contrast sensitivity in the study patients. OM

Reference

1. Hovanesian, JA, Chu R, Davies JA, Doane JF, Ohanesian, RV. The new generation Crystalens better than the rest? Ophthalmology Times Europe. 2008. Vol. 4 Issue 1.