Aspheric IOL offers better contrast sensitivity

June 23, 2008

In a prospective, randomized, contralateral study of 75 adults, eyes in which an aspheric IOL (AcrySof IQ model SN60WF, Alcon Laboratories) had been implanted demonstrated better mesopic contrast sensitivity, significantly less spherical aberration, and significantly less total higher-order aberrations compared with eyes in which a standard spherical IOL (AcrySof model SA60AT, Alcon Laboratories) had been implanted. Cumulative uncorrected visual acuity and best-corrected visual acuity were equivalent between both groups.

Key Points

Eyes in which an aspheric IOL (AcrySof IQ model SN60WF; Alcon) had been implanted demonstrated superior contrast sensitivity and significantly less spherical aberration than eyes in which a standard spherical IOL (AcrySof model SA60AT; Alcon) had been implanted, said W. Andrew Maxwell, MD, PhD, speaking at American Society of Cataract and Refractive Surgery annual meeting in May.

Dr. Maxwell, a private practitioner in Fresno, CA, based his comments on findings from a prospective, randomized, observer- and subject-masked multicenter study. He and his colleagues who participated in the study followed 75 patients who had the aspheric IOL implanted in one eye and the spherical IOL implanted in the other.

The postoperative follow-up visits at 90 and 120 days (after the second eye surgery) included measurement of uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), spherical aberration, contrast sensitivity under mesopic conditions with and without glare (using the CSV-1000 chart, Vector Vision), and root mean square (RMS) values of total higher-order aberrations (HOAs).

"The mean contrast sensitivity with the aspheric lens was statistically significantly better at 6 cycles per degree (cpd), both with and without glare," Dr. Maxwell said.

Measurements of mean contrast sensitivity at 6 cpd under mesopic conditions without glare were 1.58 ± 0.40 log units (p = 0.0048) for the aspheric lens, compared with 1.47 ± 0.46 log units for the spherical lens. The aspheric lens also performed significantly better under the same conditions with glare (1.44 ± 0.50 log units, p = 0.0132) compared with the spherical lens (1.34 ± 0.52 log units)

Mean spherical aberration values were significantly lower for the aspheric lens. "Mean spherical aberration with the aspheric lens was 0.12, which is what this lens is intended to end up with," Dr. Maxwell said.

Analyses of total HOAs revealed significantly lower RMS values for the aspheric lens compared with the spherical controls.

"In this study, the aspheric lens demonstrated better mesopic contrast sensitivity, significantly less spherical aberration, and significantly less total HOAs than the standard spherical lens," Dr. Maxwell said.

The aspheric lenses may have additional benefits not shown in the data gathered in this study, he added.

"We conducted very elaborate night-driving simulation studies and found that the eyes that had the aspheric lens performed significantly better than the eyes that had the regular spherical lens," he concluded.