Anterior Segment Cataract and Refractive
Advances in Single-optic Accommodating Intraocular Lenses John A Hovanesian, MD
Clinical Instructor, University of California, Los Angeles Jules Stein Eye Institute, and Private Practice, Harvard Eye Associates, Laguna Hills, California
Abstract
This article reviews the evolution of single-optic accommodating intraocular lenses (IOLs) from the development of the first commercially available model, the Crystalens AT-45, through to newer models of these presbyopia correcting IOLs, including the Crystalens AO, the Lenstec TetraFlex, the Human Optics 1-CU, and the Tekia Tek-Clear. Current clinical data for all lenses are reviewed, as well as the importance of a thorough pre-operative work-up in order to ensure success with these lenses.
Keywords Accommodating intraocular lenses (IOLs), presbyopia, baby boomers, quality of vision
Disclosure: John A Hovanesian, MD, is a consultant to Bausch & Lomb and Abbott Medical Optics. Received: September 15, 2010 Accepted: February 22, 2011 Citation: US Ophthalmic Review, 2011;4(1):49–51 Correspondence: John A Hovanesian, MD, 24401 Calle De La Louisa, Suite 300, Laguna Hills, California 92653. E:
DrHovanesian@harvardeye.com
The ‘baby boomers’, those born between 1946 and 1964, are now in their 60s, 50s, and late 40s. Unlike previous generations, baby boomers view the world with a future-forward perspective. According to a report published in January 2010, baby boomers feel younger than they actually are and fully expect that medical breakthroughs will allow them to live past 100. However, they are not completely satisfied with their lives: virtually all members of this generation want to make substantial life changes that include taking better care of their physical health. Hand-in-hand with this fact is that baby boomers promise to wield considerable buying power.1 These are certainly interesting facts, but how do they relate to advancements in single-optic accommodating intraocular lenses (IOLs)? Quite simply, for this generation, the handicap of presbyopia is not an acceptable situation. Furthermore, after cataract surgery, this population increasingly expects that they can reduce or eliminate the need for glasses. For a growing number of baby boomers, accommodating IOLs represent an effective choice. Clinical studies have demonstrated that accommodating IOLs can reduce or eliminate the need for glasses following implantation, while providing a good range of near, intermediate, and distance vision. Finally, because the optic is a either a spherical or aspheric monofocal, patients do not experience the side effects seen with multifocal IOLs, such as glare, halos, and loss of contrast sensitivity.2
Although the use of accommodating IOLs is on the rise today, the story of these IOLs actually dates back approximately 20 years to when ophthalmologist Stuart Cumming began to notice that patients implanted with a 10.5mm plate haptic IOL could read even though they were close to emmetropia. When Cumming refracted these patients, even if they were best-corrected for distance, the patients were able to read at J3 or better under dim light. Slit-lamp examinations in these patients found that the plate haptic lenses had a tendency to vault more posteriorly than was observed with a three-piece IOL. To confirm these observations, an
© TOUCH BRIEFINGS 2011
ultrasound study was performed and found that the plate haptic lenses consistently moved to the posterior part of the capsular bag and compressed the vitreous 50% of the time when the patients accommodated to read.
The ultrasound study found that the most anterior location was only 0.77mm in front of the original location of the posterior capsule. By comparison, when three-piece IOLs were looked at, this lens design reduced the vitreous cavity only 20% of the time and lengthened it by as much as 2.17mm. As a result of this work, Cumming began to develop a new lens that was designed to increase accommodation. The first prototype was implanted in 1991, with the design being modified as Cumming and his colleagues worked to achieve the ideal optic/haptic combination. Thirteen years later, in 2003, the Crystalens AT-45 was approved for use in the US by the US Food and Drug Administration (FDA) and a new era in IOL surgery and presbyopia correction had begun.
The main concept of the Crystalens IOL was to make the optic smaller than standard IOLs while the haptics were designed to be longer. The optic was 4.5mm for the original AT-45 model. The reason for reducing the optic size was to create a greater range of travel for a given angle of deflection. With this design, the Crystalens is intended to have two mechanisms of action: forward axial movement of the lens and optic arching. When implanted in a posterior vaulted position within the capsular bag, the accommodative process causes the ciliary muscles to contract, displacing the vitreous mass, and causing forward motion of the Crystalens.3
Available Single-optic Accommodating Intraocular Lenses
Since the commercial introduction of the Crystalens, other manufacturers have introduced single-optic accommodating IOLs. Here, we will briefly
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