27 New-Technology Intraocular Lenses: The Next Generation
27.1 Introduction
Spherical monofocal intraocular lenses (IOLs) were traditionally the artificial lenses of choice, but new-technology IOLs have become widely desirable in the last decade. Major advances have been made in recent years for treating cataracts and presbyopia. Novel multifocal, accommodating, and toric IOLs have revolutionized cataract surgery. These new-technology IOLs provide improved quality of vision, maintain or induce spectacle independence, correct astigmatism, correct presbyopia, and possibly restore true accommodation. Many of these new-technology IOLs are widely available throughout Europe and are currently undergoing clinical trials in the United States to attain Food and Drug Administration (FDA) approval. These innovative IOLs vary in shape, size, and composition. What was once limited to monofocal IOLs has now grown into an assortment of multifocal, trifocal, pseudoaccommodating, and accommodative lenses. With many more IOLs making their way into the clinical setting, technology has brought us one step closer to making visual outcomes after cataract surgery as exceptional as with a healthy, natural lens.
Chapter 3 covered a variety of new-technology IOLs in use today that have allowed surgeons to do more than simply replace the natural lens with a monofocal IOL. This chapter discusses the next generation of technology, which promises to address some of the persistent shortcomings in our field. Table 27.1 provides an overview to novel new-technology IOLs, many of which are not yet available clinically.
|
Characteristic |
Lens |
Manufacturer |
Characteristic |
FDA Approval |
CE Mark |
|
Monofocal open capsular bag device |
Zephyr |
Anew Optics |
Open capsular bag device |
No |
No |
|
CleaRing |
Hanita Lenses |
Square-edged design ring; can implant lens of choice |
No |
No | |
|
Harmoni |
ClarVista Medical |
Two component system—base and optic |
No |
No | |
|
Light adjustable lens (LAL) |
Calhoun Vision |
Composed of silicone polymer matrix containing photosensitive macromere molecules, which undergo photopolymerization in response to ultraviolet light and cause a change in shape |
No |
Yes | |
|
Sapphire AutoFocal |
Elenza |
Microsensors detect the changes in pupil size; connected to an electroactive element that adjusts the focusing power |
No |
No | |
|
Lens Refilling |
N/A (Jinshikai Medical Foundation Nishi Eye Hospital) |
Varying volumes of silicone polymers are injected into the capsular bed beneath an accommodating-membrane lens |
No |
No | |
|
SmartIOL |
Medennium Inc. |
30 mm rod composed of a thermodynamic material that reconfigures itself into a natural lens shape at human body temperature |
No |
No | |
|
Liquilens |
Vision Solutions Technology |
Gravity-dependent lens composed of two immiscible fluids of different refractive indices within one optic |
No |
No | |
|
Phaco-Ersatz |
N/A (Ophthalmic Biophysics Center at Bascom Palmer Eye Institute) |
Polymer injected into capsular bag using lens refilling technique after phacoemulsification |
No |
No |
27.2 New-Technology Monofocal IOLs
Used for many years, monofocal IOLs are now the standard of care for cataract surgery. Despite a relatively limited number of FDA-approved IOLs available in the United States, European surgeons benefit from a wider range of monofocal IOLs with various options, such as the aspheric/non-aspheric profile, the biomaterial of the lens (one-piece vs. three-piece IOL), and the hydrophobic/hydrophilic characteristics. Two other important aspects of IOLs are their capacity to induce postoperative glistening and postoperative posterior capsule opacification (PCO).
Glistenings are fluid-filled microvacuoles that form in the optic of the IOL in an aqueous environment. They have been found in many lens types, but have been found most frequently in hydrophobic acrylic IOLs, which are the most commonly implanted lens type in the United States. Glistenings form within the superficial layer of IOLs, potentially causing light scattering, thus inducing a deleterious effect on the postoperative quality of vision (see Fig. 2.2, Chapter 2).s. Literatur , 2 For more information please see Chapter 13.
Although many advances have been made in improving visual acuity since the introduction of new-technology IOLs, PCO still poses a barrier to successful cataract surgery outcomes. PCO results from the migration of epithelial cells along the capsule, hence creating an opaque layer at the back of the capsule, causing blurry vision for the patient. Many studies have shown that IOL design represents a nonnegligible factor in epithelial cell migration. Indeed, results have shown that the rate of PCO is lower with square-edged IOLs than with round-edged IOLs. Square-edge IOLs exert 60 to 70% more pressure on the posterior capsule at the optic edge than round-edge IOLs, thus providing a physical barrier to lens epithelial cells as they migrate within the capsular bag. 3 , 4 To prevent PCO, new monofocal IOL designs have emerged in various materials, shapes, and sizes.
27.2.1 Open Capsule Bag Devices
The open capsule bag devices were developed with the goal of reducing PCO. This device creates a separation between the anterior and posterior capsule that allows for increased movement of fluid within the space. This is believed to reduce the growth factor levels available within the capsular bag and create a barrier by the haptic for the proliferation of lens epithelial cells. This new implantation method showed promising results with low PCO formation rates.
Zephyr (Anew Optics)
Anew Optics is developing a new IOL design, Zephyr, based on maintaining an open capsule and allowing circulation of the aqueous humor. Zephyr is a modified one-piece hydrophilic acrylic monofocal IOL lens that keeps the anterior and posterior capsule separated from the haptics, hence maintaining the natural curvature of the capsular bag. This IOL also incorporates five apertures between the haptics and optic to allow nutrient flow throughout the capsule bag system (Fig. 27.1). The lens is fully circular and has an overall diameter of 8.8 mm. Researchers hypothesized that an open capsular bag enhances endocapsular inflow of aqueous, thus reducing PCO without the need for a square-edged design.
Leishman et al performed a study evaluating the rate of PCO after Zephyr versus a one-piece hydrophilic acrylic IOL (model C-flex, Rayner) implantation in New Zealand rabbits. The results were conclusive, with a PCO score of 0 at 4 weeks in the Zephyr group versus a PCO score pf 1.75 ± 0.5 in the control group (p = 0.005). 5 A recent presentation by Wormstone at The Association for Research in Vision and Ophthalmology (ARVO) 2014 annual meeting in Orlando showed similar results after comparing Zephyr versus AcrySof (Alcon) on cadaver eyes. 6 The company announced that, in the future, toric and accommodating designs will be implemented.
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