Additional mechanism of action possible in accommodative lens

July 15, 2005

Washington, DC—The crystalens (eyeonics), an accommodating IOL approved for use in cataract patients, provides distance, intermediate, and near vision 3 years after implantation that are slightly better than the 1-year results. Optical tilt or optic flexure with induced astigmatism in conjunction with the traditional mechanism of action is hypothesized to play a role in the near visual acuity, according to Steven J. Dell, MD, speaking at the American Society of Cataract and Refractive Surgery (ASCRS) annual meeting.

The near-vision results showed the same pattern for binocular uncorrected near vision. At 1 year and 3 years after implantation, 72.4% and 80.6%, respectively, had J1 or better vision, and 93.7% and 96.8%, respectively, had J2 or better vision. All patients at 3 years had J3 or better compared with 98.4% at 1 year (Figure 1), reported Dr. Dell, in private practice in Austin, TX.

"Optical tilt or flexure with induced astigmatism may play a role in near acuity," Dr. Dell explained. "In our practice, we began to see patients with central areas of astigmatism on wavefront maps as they accommodated.

"This would be consistent with slight tilting or bending of the optic itself with accommodation," he added. "This tilt may increase the depth of focus and explain why some patients with a crystalens implanted see better at near than might be expected by the degree of forward movement of the optic."

"Some patients who have had the crystalens implanted have near acuity that surpasses the level expected from this degree of movement for their particular IOL power," Dr. Dell said-making him question if another mechanism, besides the pseudoaccommodation common to all IOLs, was at work.

The mechanism of the crystalens that he and Kevin Waltz, MD, have proposed is accommodative arching. Both Dr. Dell and Dr. Waltz have reported on a comparison of near fixation with far fixation that showed changes on wavefront testing that could be consistent with bending or tilting of the optic. The difference map shows induced astigmatism at near.