Multifocal and Extended Depth of Focus Intraocular Lens Implants
The number of IOL options for patients undergoing cataract surgery has increased in recent years. Patients may select a traditional monofocal IOL with a refractive target of emmetropia, mild myopia, or monovision, or they may opt for a multifocal extended depth of focus (EDOF) or accommodating IOL for greater range of focus.
Several multifocal IOLs (MFIOLs) are FDA approved in the United States. Since the first IOL was introduced, lens design has evolved to include zonal refractive and apodized diffractive IOLs. The zonal refractive lens design uses refractive power changes from the center of the lens to the periphery to provide distance and near correction. In contrast, diffractive lens designs employ a series of concentric rings to form a diffraction grating (see BCSC Section 3, Clinical Optics) to create 2 separate focal points for distance and near vision (Fig 9-6). Some diffractive lenses are apodized, meaning that the diffractive step heights are gradually tapered to yield a more even distribution of light, theoretically allowing for a smoother transition among images from distance to intermediate and near targets. Recently, the FDA approved the first diffractive EDOF IOL, the TECNIS Symfony (Johnson & Johnson Vision). An example of a zonal refractive lens is the ReZoom lens (Johnson & Johnson Vision, Santa Ana, CA), no longer available in the United States. Various styles are available in Europe. Examples of this type of lens include the M-flex T (Rayner, Hove, United Kingdom) and the LENTIS Mplus (Oculentis GmbH, Berlin, Germany) (Fig 9-7). Trifocal IOLs are also available in Europe; examples are FineVision (PhysIOL, Liège, Belgium), and the AT LISA tri (Carl Zeiss Meditec AG, Jena, Germany).
The clinician should have a comprehensive discussion with each patient regarding the benefits and visual outcomes of MFIOLs to ensure that the patient has realistic expectations. The preoperative examination is equally crucial as it is critical to rule out any macular or other ocular diseases preoperatively, as MFIOLs are contraindicated in eyes with preexisting poor vision potential. In addition, any ocular abnormality that could increase systemic ocular aberrations (eg, corneal scarring, irregular astigmatism, dry eye) may significantly decrease image quality with these lenses. The clinician should carefully consider the possibility of patient dissatisfaction with the quality of vision after MFIOL implantation.
Figure 9-6 Example of a diffractive multifocal intraocular lens. Left, schematic of the frontal view. Right, schematic of the side view.
(Left image courtesy of Abbott Medical Optics Inc.)
Figure 9-7 Example of a zonal refractive multifocal intraocular lens. Left, a schematic frontal view. Right, a schematic lateral view of the rotationally asymmetric, multifocal sector lens, which is made from a combination of 2 spherical surfaces of differing radii.
(Illustration by Mark Miller from information courtesy of Oculentis GmbH.)
Patients with suboptimal results or who are dissatisfied with the quality of vision should undergo a comprehensive evaluation from the ocular surface to the macula. The clinician should exclude possible causes of vision disturbance, such as dry eye, residual refractive error, decentered lens or pupil, irregular astigmatism, vitreous opacities, cystoid macular edema, or epiretinal membrane. Postoperative capsular opacification is of greater concern with MFIOLs because minimal changes in the capsule can cause early deterioration in vision. To achieve optimal vision, Nd:YAG laser capsulotomy may be required earlier or more frequently in patients with MFIOLs than in patients with monofocal IOLs. However, if IOL exchange is being contemplated, Nd:YAG laser capsulotomy should be deferred. Other possible causes of vision disturbance should be excluded before an IOL exchange is considered. MFIOLs may cause glare and halos around lights at night, although newer MFIOLs incorporate technology that substantially reduces (but does not generally eliminate) these optical phenomena. Symptoms may be reduced through the use of nighttime driving glasses or instillation of topical brimonidine drops to reduce mesopic pupil size. In addition, most of these symptoms will decrease over time through neuroadaptation.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.