In May 2005, the Centers for Medicare & Medicaid Services (CMS) issued a ruling that gives patients the option to pay out of pocket for new technology IOLs when undergoing cataract surgery. Among the lenses for which patients may pay a premium are presbyopiacorrecting designs, categorized as accommodating and multifocal (or pseudoaccommodating). Although their mechanism of action is not fully understood, accommodating IOLs are designed to move forward (thus changing the effective IOL power) in response to the ciliary muscle's contraction to focus vision at near or intermediate distance. In contrast, multifocal IOLs are designed to deliver a range of vision at various distances through differently powered zones located on the lens' optic.
In clinical trials, the presbyopia-correcting IOLs available in the United States performed well in healthy eyes when the subjects had reasonable expectations. The technologies' role in eyes with retinal, optic nerve, or ocular surface pathology, however, is controversial. This article provides a brief overview of IOLs for presbyopic correction and shares recommendations on their use based on our experience.
ACCOMMODATING IOLS
The Crystalens
The first Crystalens accommodating IOL (Bausch +
Lomb, Rochester, NY) was implanted in England in 1991.
The FDA approved the AT-45 model in November 2003.
Today, the only accommodating lenses available in this
country are the Crystalens Five-0, the Crystalens HD, and
the Crystalens AO.
These IOLs feature a 5-mm silicone optic with hinges and square edges. Square silicone plate haptics with T-shaped polyamide loops help provide stabilization and centration of the IOL within the capsular bag. For eyes requiring corrective powers of 17.00 D and higher, the length of the IOL is 11.5 mm. A 12-mm IOL addresses corrections of less than 17.00 D.
The Crystalens Five-0 provides excellent distance and intermediate vision without the reduction of contrast sensitivity that is associated with multifocal IOLs. The blended bispheric optic of the Crystalens HD is supposed to enhance near vision while maintaining excellent contrast sensitivity. Released in January 2010, the Crystalens AO represents the first aberration-free accommodating IOL with aspheric optics.
Potential challenges associated with the Crystalens technology include inaccurate refractive outcomes (due to the varying position and movement of the IOL) and inadequate near vision1 (Table 1).
On the Horizon
The Synchrony (Abbott Medical Optics Inc., Santa Ana, CA) has a negatively powered posterior optic and a plus-powered anterior optic that are connected by spring haptics. Upon accommodative effort, the distance between the two optics increases.2 The Tetraflex accommodating lens (Lenstec, Inc., St. Petersburg, FL) is another monofocal IOL that moves with accommodative effort.3MULTIFOCAL IOLS
ReZoom
The ReZoom (Abbott Medial Optics Inc.) is a secondgeneration
zonal refractive multifocal IOL that received
FDA approval in March 2005. This hydrophobic acrylic
lens has five zones; zones 1, 3, and 5 are distance dominant,
and zones 2 and 4 are near dominant. Aspheric
transitions between the zones are designed to provide
improved intermediate vision. This three-piece lens has a
6-mm optic and PMMA haptics.
The ReZoom IOL provides good vision at distance and intermediate distance, but patients often require spectacle correction at near.4 Surgeons should warn patients preoperatively about the potential for unwanted visual phenomena such as glare and halos after surgery.5 With the recent availability of the Tecnis Multifocal lens (Abbott Medical Optics Inc.), the utilization of the ReZoom lens has decreased significantly.
Tecnis Multifocal
The Tecnis Multifocal is a clear hydrophobic acrylic
lens. It offers a pupil-independent, fully diffractive posterior
surface designed to optimize vision under all lighting
conditions. The IOL's wavefront-designed aspheric anterior
surface was engineered essentially to eliminate spherical
aberration and thereby enhance the quality of the
patient's vision at all distances. The +4.00 D add power
attempts to optimize near visual acuity at a preferred
reading distance of 33 cm.
US clinical results demonstrate that over 94% of patients are able to function comfortably without glasses at all distances after the bilateral implantation of the Tecnis Multifocal IOL.6 This IOL was also designed to reduce chromatic aberration and provide protection from ultraviolet light. The three-piece lens may be placed in the ciliary sulcus. Centration of the IOL is critical to obtaining optimal visual results. Glare and halos appear to be less problematic with this lens compared with previous multifocal designs.6
AcrySof Restor
The FDA initially approved the AcrySof Restor IOL
(Alcon Laboratories, Inc., Fort Worth, TX) in March 2005.
This single-piece acrylic IOL was the first to offer apodized
diffractive technology that allows for both distance and
near vision. The term apodization refers to the gradual
reduction or blending of the heights of the diffractive
steps. Apodization, aspheric optics, and the change from
a +4.00 to a +3.00 D add power are intended to improve
the quality of patients' vision at all distances.
The AcrySof IQ Restor IOL +3.0 D is now the leading presbyopia-correcting IOL in the US marketplace.7 This design became available last year and has significantly improved patients' intermediate vision to complement the IOL's already excellent profiles for distance and near vision.8,9 The AcrySof Restor lenses feature blue-blocking and ultraviolet light-filtering technology that may prevent the development and/or progression of macular degeneration, but this remains a subject of debate.10 Patients should be warned of the possibility of postoperative glare and halos, but the incidence of these phenomena is dramatically lower with the most recent iteration of this IOL.11,12
OUR RECOMMENDATIONS
Overview
As with any technology, patient selection is critical.
Individuals with glaucoma often may be less-than-ideal
candidates for presbyopia-correcting IOLs. These individuals
simply may not receive the benefits of accommodating
or multifocal IOLs due to limited visual fields and diminished
contrast sensitivity. Furthermore, the potentially negative
impact of multifocal IOLs on clinicians' ability to follow
visual fields is a concern. Currently, we recommend
using standard visual field testing techniques and using
near vision corrections per one's usual protocols.
Ocular Hypertension and Early Glaucoma
We would characterize glaucoma as a relative contraindication
for the placement of accommodating and
multifocal IOLs. This technology may bring tremendous
satisfaction to patients who have well-controlled ocular
hypertension or early glaucoma without any visual field
loss. A thorough, well-documented discussion of the
possible risks of decreased visual function with progressive
glaucomatous damage is essential, however, with all
glaucoma patients undergoing cataract surgery.
Moderate Glaucoma
We tend to avoid multifocal IOLs for patients with
moderate, well-controlled glaucoma and mild visual
field loss, because their contrast sensitivity may already
have diminished, and the risk of a dissatisfied patient is
considerable. Because the Crystalens functions much
like a monofocal lens, it may be an option in patients
who have reasonable expectations for their outcome.
Caution, however, is certainly warranted here.
Progressive or Advanced Glaucoma
We do not recommend the use of presbyopia-correcting
IOLs in patients with advanced or uncontrolled glaucoma.
The benefits of these lenses will be minimal or nonexistent
for these individuals. More likely, the IOLs will provide a
lesser quality of vision than an aspheric or toric monofocal
design. We also favor monofocal IOLs for patients undergoing filtration surgery. After less invasive procedures such as
Trabectome surgery (NeoMedix Corporation, Tustin, CA)
and canaloplasty (iScience Interventional, Menlo Park, CA),
we have had some success with the Crystalens in select
patients. Caution is clearly recommended in these cases.
CONCLUSION
Presbyopia-correcting IOLs offer certain glaucoma
patients the promise of an increased range of vision and
more independence from spectacles. Surgeons must
ensure, however, that these individuals have realistic expectations
for their outcomes. We prefer monofocal IOLs for
most glaucoma patients, but in our experience, select
patients benefit from the newer accommodating IOLs.
The judicious use of multifocal IOLs in patients with documented
well-controlled ocular hypertension or glaucoma
with full visual fields may also be reasonable.
Randall E. Cole, MD, is a cataract and refractive surgery consultant at Boozman-Hof Eye Clinic, PA, in Rogers, Arkansas. He receives research support from Abbott Medical Optics Inc. and is a speaker for Alcon Laboratories, Inc. Dr. Cole may be reached at (479) 246-1700; dreyerecole@aol.com.
Steven D. Vold, MD, is a cataract and glaucoma surgery consultant at Boozman-Hof Eye Clinic, PA, in Rogers, Arkansas. He receives research support from Alcon Laboratories, Inc. Dr. Vold may be reached at (479) 246-1700; svold@cox.net.
