Subjective and objective testing demonstrate accommodative amplitude of lens

May 15, 2007

Subjective and objective accommodation in patients with a dual-optic accommodating IOL implanted bilaterally were measured in a pilot study. Accommodation was adequate in subjective testing and significantly greater than in controls with an acrylic foldable monofocal IOL. Objective evaluations demonstrated movement of the anterior optic.

Key Points

Victor Bohorquez, MD, and Ricardo Alarcon, MD, Department of Ophthalmology, ServiOftalmos, Bogota, Colombia, measured subjective and objective accommodative amplitude in 25 patients with the dual-optic IOL implanted bilaterally. The results in those patients were compared with those measured in an age-matched control group of 10 patients in whom a foldable acrylic monofocal IOL (AcrySof, Alcon Laboratories) had been implanted bilaterally.

Accommodation was investigated subjectively using push up/push down testing. Measurements for push up to first blur, push up to sustained blur, and push down were collected through the best-corrected distance visual acuity (BCDVA) at 40 cm and with use of minimum near add power.

"We also found that maximum binocular subjective accommodation achieved in the dual-optic accommodating IOL group ranged up to almost 6.0 D in push up testing, and although the accommodative amplitude values tended to be higher with the push up testing, the accommodative amplitudes achieved in push down testing are adequate for functional near vision," he noted.

Further analyses showed that the results of the first blur and sustained blur tests in patients in whom the dual-optic IOL had been implanted were significantly correlated (p = 0.002) with their distance corrected near visual acuity, i.e., more accommodation was achieved in patients with better near visual acuities.

Lens movement

The investigators also used objective techniques to evaluate the accommodating mechanism of the dual-optic IOL, including ultrasound biomicroscopy (UBM) imaging to investigate movement of the anterior lens and ray-tracing aberrometry (iTrace, Tracey Technologies) to capture changes occurring when focus was shifted from distance to near. Subjects evaluated with UBM had had the dual-optic lens implanted for at least 1 year.

UBM imaging revealed that the two optics of the implant remained in close proximity to each other, providing emmetropia, when the fellow eye was stimulated for distance vision. The anterior optic, however, moved forward when near vision was stimulated in the fellow eye using a handheld ETDRS chart.

"This technique uniquely allows measurement of the three-dimensional movement of the anterior optic in the dual-optic IOL system," Dr. Bohorquez explained.