9 Presbyopia-Correcting IOLs: Patient Selection and Satisfaction
9.1 Introduction
Cataract surgeons have witnessed tremendous advances in instrumentation, materials, surgical technique, and technology over the past several decades that have enabled them to achieve excellent visual outcomes offering greater safety and greater range of vision after surgery. Critical to the great success of modern era cataract surgery has been the evolution in intraocular lens (IOL) technology and design. However, until recently, IOL options were limited to monofocal lenses. These lenses are successful in providing uncorrected vision for one focal point but leave most individuals dependent on some correction for other distances. The newest wave of IOL innovation has provided surgeons with several alternatives with the goal of restoring the ability to focus both at near and far without complete dependence on spectacles. These lenses can be broadly divided into two categories: accommodating and multifocal IOLs. Currently, there are five Food and Drug Administration (FDA)-approved IOLs available to treat presbyopia in the United States: Crystalens/Trulign (Bausch & Lomb, Inc.) (Fig. 9.1, Fig. 9.2, respectively), ReZoom (Abbot Medical Optics, Inc.), ReSTOR (Alcon) (Fig. 9.3), and Tecnis (Abbot Medical Optics, Inc.) (Fig. 9.4). Similar to the boom in new technology that made new implants and devices available to cataract surgeons, the advances in communications have made information regarding cataract surgery readily available to patients to the point that patients now present to the office well prepared and up to date on their surgical options, and they have started to expect perfect surgical outcomes, with good vision at both distance and near without the need for corrective lenses. 1 Patients also have an interest in and willingness to pay for the outcomes they desire. 2
9.2 Presbyopic IOLs
Being aware of the variety of IOLs currently available on the market and of their mechanism of action is vital to ensuring proper patient selection and satisfaction. This section focuses on the various types of multifocal IOLs, which function based on a common principle—they simultaneously present near and far focal lengths to the retina, without the need for IOL movement. This is generally accomplished by using refractive or diffractive optics. The major drawbacks shared by all types of multifocal IOLs are the adverse visual phenomena of glare, haloes, and reduced contrast sensitivity. A more detailed discussion of the individual multifocal IOL types follows.
Some multifocal IOLs (e.g., ReSTOR) use different but complementary optical principles (diffraction and apodization) to achieve distance and near vision. Apodization is the process that diminishes diffraction fringes which appear around the images of bright points of light. This is accomplished by a gradual decrease in the height of the concentric steps from the center toward the periphery of the optic surface. Higher steps direct more light to a near focal point, whereas lower steps direct more light to distant focal points. This transition between steps aims to minimize visual disturbances as well as distribute light energy to distance focus with greater pupil size. 3
Some diffractive IOL models (e.g., Tecnis) highlight a posterior diffractive surface and a full diffractive optic. The potential advantages of this type of lens are improved near vision in a dimly lit environment and improved depth of focus due to a posterior diffractive surface that results in a longer focal point.
Refractive multifocal IOLs (e.g., ReZoom) enable good vision through a range of distances. However, in exchange for improved near vision, loss of contrast sensitivity and increase in glare and halos remain a problem. This IOL is no longer commonly used in the United States.
Toric multifocal IOLs (e.g., Rayner M-flex, Alcon ReSTOR Toric) are also available and have shown promising results in patients with significant levels of astigmatism. However, these lenses are currently not FDA approved for use in the United States. There are also trifocal multifocal IOLs available outside the United States, which are reported to reduce 5% more diffracted light than bifocals.s. Literatur
As of 2014, only one accommodating IOL is FDA approved in the United States (Crystalens). A new subtype (Trulign) that incorporates a correction for astigmatism has recently been placed on the market. The design of the lens is expected to allow the IOL to move anteriorly or posteriorly, depending on the accommodative forces of the eye. This feature provides the patient with uncorrected distance and intermediate vision with workable near vision. In contrast to multifocal IOLs, the use of an accommodating IOL significantly reduces the adverse effects of glare and halos because the lens projects a single focal point to the retina at a given time. However, most patients cannot achieve sufficient accommodation for functional near vision and might require reading glasses. Other accommodating IOLs currently available in Europe have reported promising results. 5
9.3 Patient Selection
A number of considerations should be taken into account when choosing the best candidates for presbyopia-correcting IOL implants. Patient expectations, ocular diseases, pupil size, and refractive errors are all important factors that should be examined. In addition, the preoperative discussion is crucial to explain the limitations of the various available IOLs and thus establish realistic expectations.
9.4 Patient Expectations
The first consideration in IOL selection is to understand patients’ expectations and identify patients who may not be content with the limitations of the IOLs despite successful surgery. To this end, Dell developed a questionnaire that asks patients about visual preferences, visual tasks, and personality (easygoing vs. perfectionist). 6 Patients with “type-A” personalities, especially those with perfect visual needs, are more likely to be dissatisfied with the surgical outcome with a multifocal IOL implant. Although patients with this type of personality are not precluded from having presbyopia-correcting IOLs, special care should be taken to ensure proper preoperative counseling. On the other hand, patients who are more easygoing, “type B” personalities may be more likely to accept the compromises in visual quality they are making for additional spectacle independence.
Furthermore, occupational and vocational needs are paramount when choosing presbyopic IOLs. For example, pilots and professional night drivers are poor candidates for multifocal IOLs due to the increased risk of nighttime photic phenomena. If a presbyopic IOL were to be used in these patients, surgeons could opt for an accommodating IOL because it provides the sharp distance of a monofocal optic while possibly providing intermediate/near vision. 6 Patients who spend a great deal of time using near vision in dim environments might fare better with a full optic diffractive nonapodized multifocal. 6 Patients who did not adapt well to bifocal glasses might do poorly with multifocal IOLs because these patients have already demonstrated poor adaptation to a new visual environment. 7 A monofocal IOL may be a better choice for the latter group of cataract surgery candidates.
Age also plays an important role in patient selection. Several conditions become more prevalent with age, such as optic neuropathy, macular degeneration, and ocular surface dryness, that may compound the loss of contrast sensitivity seen in multifocals. 8 One study comparing a monofocal and a multifocal IOL showed reduced contrast sensitivity in both groups but greater patient satisfaction in the younger cohort. 9 The following section provides further details on how preexisting ocular conditions might influence the choice of IOLs and the surgical outcome.
9.5 Ocular Diseases That Impact MIFOL Tolerance
Numerous factors will determine the success of any presbyopic IOL surgery, possibly none so much as having a healthy eye preoperatively. One of the biggest problems with presbyopic IOL patients is ocular surface disease, such as dry eye syndrome and meibomian gland dysfunction. Patients with dry eye already have a degree of reduced contrast sensitivity that can be exacerbated by cataract surgery. 10 Therefore, aggressive treatment of the ocular surface with a comprehensive regime is expected to improve both patient comfort and visual acuity postoperatively. In addition, optimizing the ocular surface prior to surgery may improve the accuracy of corneal measurements because it has been reported that dry eyes could lead to optical aberrations and blurry vision. 11
Other corneal irregularities, in particular corneal dystrophies, may influence surgical outcomes. Patients with epithelial basement membrane dystrophy (EBMD) are poor candidates for multifocal IOLs because the condition can produce aberrations due to an irregular corneal surface, which might affect visual outcomes. 12 Patients with Fuchs’ corneal dystrophy also need to be properly assessed and counseled preoperatively because they already have compromised contrast sensitivity and poor quality of vision, especially during the night, which can be aggravated by multifocal presbyopic-IOL implantation. 13 Due to the progressive nature of the disease, visual disturbances from the corneal guttata and decompensation will invariably worsen over time. Therefore, the visual outcome with a multifocal IOL is also expected to worsen.
Further, the potential presence of corneal scarring should also be evaluated preoperatively. Peripheral, asymptomatic scars are not a contraindication to multifocal IOL implants, but the existence of central corneal scarring can confound the visual outcome analysis following even the most perfect cataract surgery.
Preexisting astigmatism should be discussed with patients before presbyopic IOL surgery. Residual astigmatism > 1.5 diopters (D) can significantly reduce visual acuity and is one of the main causes for patient dissatisfaction following surgery.s. Literatur If toric presbyopia-correcting IOLs are not available, the surgeon must choose between the available options. Small amounts of regular astigmatism can be corrected with limbal relaxing incisions during the cataract surgery with satisfactory outcomes. However, in eyes with greater amounts of corneal astigmatism, some surgeons prefer to implant a toric monofocal IOL rather than a combination of presbyopia correction with incisional astigmatism correction.
Following cataract surgery, corneal laser refractive surgery can be used to correct small residual spherical and cylindrical errors. However, in addition to the risk of additional surgery, these procedures are commonly associated with dry eye. 15 , 16 Toric IOLs that also correct presbyopia often offer the best solution for patients with significant levels of astigmatism who also desire presbyopia correction. In patients with keratoconus, forme fruste keratoconus, pellucid marginal degeneration, and other types of irregular astigmatism, special care should be taken when considering implantation of presbyopic IOLs. In this subset of patients, corneal laser refractive surgery is not an ideal option to correct any residual error because of associated poor outcomes.s. Literatur
In patients with macular diseases, such as significant macular degeneration, epiretinal membranes, and vitreomacular traction syndrome, care should be taken when considering multifocal presbyopic IOL implants. 8 , 17 , 18 These conditions are associated with reduced contrast sensitivity, which can be worsened by multifocal IOLs, leading to a reduction in visual quality. Testing the potential for visual improvement following cataract surgery in patients with known macular pathology is therefore paramount. These tests can include simple near acuity, pinhole testing, red-stripe test, and potential acuity meter. The density of the cataract can limit fine details and impair visualization of the fundus during clinical examination. Patients with dense cataracts can be tested with blue field entoptoscopy or the Purkinje vascular entopic test, but the most useful test for macular diseases is optical coherence tomography (OCT), which can detect subtle, subclinical pathology and is often performed preoperatively in presbyopic IOL candidates.s. Literatur , 13 Other retinal diseases, such as retinitis pigmentosa, Stargardt’s disease, and advanced diabetic retinopathy are also important to consider as possible contraindications.
9.5.1 Absolute Contraindications for Multifocal IOL Implants
Ocular Conditions
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