Multifocal IOL technology: A successful step on the journey toward presbyopia treatment

By far, the most frequent refractive error in the human eye is presbyopia, ie, the loss of accommodation, a dynamic change in the dioptric power of the eye. The most widely accepted and experimentally confirmed theory of accommodation was described by Helmholtz in 1855.1 According to Helmholtz, accommodation is achieved by the release of zonular tension, with contraction of the ciliary muscle and subsequent modeling of the shape of the crystalline lens by the elastic lens capsule. Over the years, other theories about the accommodation process have been developed but because of difficulties examining the accommodative apparatus in vivo, experimental studies have been performed to investigate the mechanism. The research has found a multifactorial etiology of presbyopia, which suggests that total restoration of the accommodation process might not be easy to achieve.2 Now that refractive surgery can successfully treat many forms of myopia, hyperopia, and astigmatism, the emphasis will be on the treatment of presbyopia. Currently, 2 basic approaches can be identified for surgical presbyopia correction—an increase in the depth of focus and a restoration of accommodation in the proper sense, ie, a dynamic change in ocular refraction. The former can be achieved by multifocal intraocular lens (MIOL) implantation. Multifocal IOLs of different designs have been used for more than 20 years, but despite good distance and near visual acuity, difficulty in selecting appropriate patients, reduced contrast sensitivity, and increased glare have prevented broad acceptance. Recently, the primary MIOL concepts (refractive and diffractive) have been modified (apodization, asphericity, combination of refactive and diffractive principles), which has improved the outcome. In this issue, Zelichowska et al. (pages 2036–2042) compare new refractive and diffractive MIOLs. The authors found good visual performance at distance and near under photopic conditions with both IOL designs, but optical quality was significantly better with the diffractive design than with the refractive design. This may be of primary importance for future MIOL technology. Also in this issue, Ferrer-Blasco et al. (pages 2043–2048) investigate distance and near contrast sensitivity (CS) under photopic and mesopic conditions before and after implantation of an apodized diffractive MIOL model (SN60D3) for refractive lens exchange (RLE). The group used the Stereo Optical FACT CS chart at distance and near at 3 illuminance levels (85, 5, and 2.5 cd/m2). They found that although mesopic CS is reduced at distance and near compared with the CS at photopic conditions, mesopic contrast sensitivity did not change from the preoperative values. One can note an increasing use of MIOLs as a therapeutic approach for the correction of presbyopia worldwide, particularly with the increase in microincisional cataract surgery and RLE. To guarantee patient satisfaction, it is important to be aware of the various IOL properties and patient inclusion criteria. A differentiated patient selection in combination with optimized peri-, intra-, and postoperative management is necessary to achieve appropriate postoperative refractive results for patient satisfaction. Multifocal IOLs provide pseudoaccommodation; with recent improvements such as the addition of asphericity or apodization and good preoperative judgment in the choice of the IOL, they are being used successfully. However, true restoration is already on the horizon (eg, accommodating IOLs). The accommodative procedures currently used have at least temporarily achieved accommodative amplitudes up to about 1.0 diopter. The restoration of accommodation faces problems partly caused by remaining uncertainties about the details of the mechanism of accommodation and the development of presbyopia. Some surgical procedures are clinically applied and marketed, although they are based on concepts whose validity is not confirmed or contradict experimental evidence. Thus, it is necessary to assess the results and the presumed mechanisms critically and objectively. I am convinced that this approach will guide the way in the future to treat presbyopia in the proper sense—a dynamic change in ocular refraction.