[Comparison of high-order optical aberrations induced by different multifocal contact lens geometries]

To analyze the effects of different multifocal soft contact lens geometries on high-order ocular optical aberrations.

Thirty nonpresbyopic eyes were fitted with eight multifocal contact lenses: Soflens Multifocal High, Soflens Multifocal Low, Focus progressive, Acuvue Bifocal Add +2.00, Rythmic Multifocal Profile 1, Rythmic Multifocal Profile 2, Proclear D Add 2.00, Proclear N Add 2.00. All these contact lenses corrected the ametropia for far distance. The ocular aberrations were measured with and without each contact lens using a Hartmann-Shack aberrometer, (Zywave from Bausch and Lomb) successively after pupil dilation with one or two drops of Neo-Synephrine and wavefront decomposition in Zernike polynomials up to the 5th order.

Odd and even aberrations increased for all the tested multifocal soft contact lenses. The most significant increase was noted for the a(4.0) Zernike coefficient. The mean value of a(4.0) without contact lens was -0.178+/-0.121 microm. The contact lenses having a central zone for near addition cause the inversion of the sign of the a(40) coefficient The central far vision contact lens leads to the opposite effect, increasing spherical positive aberrations. The most significant increase in total high-order ocular aberrations were noted for Proclear D soft contact lenses (0.396+/-0.109 microm without contact lens, 0.511+/-0.123 microm with contact lens; p<0.05, +29%), for Proclear N soft contact lenses (0.396+/-0.109 microm without contact lens, 0.568+/-0.165 microm with contact lens; p<0.05 +43%) and for Acuvue Bifocal soft contact lens (0.396+/-0.109 microm without contact lens, 0.567+/-0.162 microm with contact lens; p<0.05 +43%).

Wearing multifocal contact lenses induces an increase in high-order ocular aberrations. The location of the near addition zone is related to the sign of the variation of the a(4.0) coefficient. The central near vision multifocal contact lenses seem to induce large amounts of negative spherical aberrations. The far vision contact lenses seem to induce an increase in positive spherical aberrations. The relative decentration of the lens to the pupil may explain the increase in odd high-order aberrations. These results might be useful to understand the visual complaints of patients fitted with multifocal contact lenses.