Optical properties of monovision corrections using multifocal designs for near vision.

PURPOSE: To evaluate how multiple-zone multifocal designs maximize optical performance of modified monovision corrections.

SETTING

Midwestern University, Chicago College of Optometry, Downers Grove, Illinois, USA.

DESIGN

Experimental study.

METHODS

Optical performance under monovision conditions combining monofocal, bifocal, trifocal, and designs with spherical aberration was evaluated using computer simulations of the visual Strehl ratio based on the optical transfer function in relation to the optical quality provided by design (limiting performance at best focus), through-focus performance of design (evaluating real multifocal usability), and difference between images on each eye (limiting tolerance for monovision corrections).

RESULTS

Monovision corrections with bifocal or trifocal patterns for near vision offered higher optical performance (larger area under values of the visual Strehl ratio and larger range of acceptable vision through-focus) than an aspheric design. A bifocal design with 1.5 diopters (D) of addition and centered through-focus between 2.0 D and 3.5 D had the best range above threshold (3.98 D) for a monofocal design (centered at 0 D, distance vision) combined with a bifocal design. The largest optical disparity was achieved with 2 monofocal designs (1 centered at 0 D, 1 centered at 4.0 D).

CONCLUSIONS

Bifocal and trifocal combinations produced higher optical quality (5%) and through-focus performance (35%) than spherical aberration designs. For any given amount of tolerable optical disparity in presbyopia, a combination of monofocal and bifocal/trifocal designs offered better optical performance than a spherical aberration design. Bifocal and trifocal designs can be implemented in laser in situ keratomileusis equipment to improve conventional monovision and will soon be available in new multifocal contact and intraocular lenses.

FINANCIAL DISCLOSURE: The author has no financial or proprietary interest in any material or method mentioned.