MULTIFOCAL INTRAOCULAR LENSES - STATE-OF- THE-ART

Besides the diffractive multifocals, which produce a second focus for near vision by means of diffraction rings, there are different refract ive multifocal IOL types with 2-7 refractive zones or an aspheric/sphe rical construction principle. Long-term results. 2 years after implant ation of diffractive multifocal IOLs, the corrected distance and near acuities were unchanged compared to the 3-month results. The uncorrect ed distance acuity was, however, slightly decreased due to a minus shi ft of refraction to - 1.2 D. The contrast sensitivity was improved aft er 2 years. Multi- versus monofocal IOLs: After diffractive multifocal IOL implantation, the near acuity with distance correction only was m arkedly improved compared to monofocal IOLs. All other acuity data did not differ between multi- or monofocal lenses. The contrast sensitivi ty (at low contrasts and high spatial frequencies) and mesopic visual acuity (without and with glare) were reduced compared to monofocal pse udophakic eyes. Near aniseikonia and binocular functions: In unilatera l multifocal pseudophakia (monofocal IOL in fellow eye), a near anisei konia up to 8% was found. The width of fusion was significantly lower than in bilateral multifocal pseudophakia, whereas the stereopsis show ed no difference. Determinants of bifocal function: In 7.1% of our cas es, no bifocal function (BFF) was present after implantation of diffra ctive multifocal IOLs. These patients exhibited a significantly higher age as well as higher pre- and postoperative astigmatism, when compar ed to patients with good BFF. Optical performance of different multifo cal IOLs: By means of an optical system, described by Reiner, images o f intraocular lenses can be projected into the eye (''optical implanta tion''); thus, the optical performance of IOLs can be judged subjectiv ely. Using this method, the refractive 2- and 3-zone models performed best within the multifocal group (contrast sensitivity not significant ly worse than that of monofocal IOL), when viewing a low-contrast char t (Regan 4%). All other multifocal lenses (diffractive, aspheric/spher ical, refractive 5- and 7-zone models) were significantly inferior to the monofocal IOL. Conclusions: Implantation of multifocal IOLs should presently be restricted to special indications, particularly to the d istinct patient request to dispense with wearing near or bifocal glass es, if possible. Because of the reduction in contrast sensitivity and mesopic vision and the increased glare sensibility, multifocal IOLs sh ould not be implanted especially in professional car drivers. There ar e, however, differences in optical performance between the various mul tifocal IOL types. Further improvements, in particular concerning lens technology, will presumably extend the present spectrum of indication s.