Abstract

A multifocal intraocular lens (IOL) of diffractive design is currently producing very promising clinical results. The lens has two optical powers and is implanted after cataract extraction. One power is used for distance vision, and the other for near vision. The image from the second power is highly defocused in each case. The ophthalmic community is investigating methods of measuring image contrast and resolution, because of the unique properties of multifocal lenses of various designs. One possible measure is the modulation transfer function (MTF), but discussion shows that any MTF measurement of a multifocal lens must be treated with caution. The diffractive multifocal IOL has two high resolution foci, yet the lens MTF is distinctively different from that of an equivalent conventional monofocal lens. This can be explained by the design of the lens, since the contrast effects of the multifocal lens are well-controlled and perform a useful function—the provision of a second lens power.

© 1989 Optical Society of America