Following cataract surgery, a conventional lens implant will usually provide clear vision at a single distance, but you will still need glasses for the correction of presbyopia. This means that if your lens implants are for distance vision, you will need reading or computer glasses for close-up vision.
Monovision
If appropriate for your individual situation, you may opt for monovision correction to enhance your reading vision. This is where one eye receives a distance lens implant and the other receives a lens for closer up. There are some limitations and compromises associated with this, however, which you can discuss with your surgeon.
Presbyopia-correcting lens implants
Over recent years, many improvements in lens implants have allowed for the development of presbyopia-correcting IOLs. Where appropriate, for presbyopic patients who do not qualify for laser refractive surgery and do not want to rely on reading glasses, these premium lens implants may offer significant advantages over conventional monofocal IOLs by enabling clear vision at multiple distances. Depending on the condition of your eyes, presbyopia-correcting lenses may be implanted to expand your range of clear vision, allowing you to see well at a broader range of distances with reduced need for eyeglasses.
Presbyopia-correcting lenses can be divided into two broad categories—multifocal and accommodative.
Multifocal lens implants
Multifocal lens implants consist of multiple zones of lens power that produce more than one focal point, allowing for enhanced vision at both near and far. The multifocal IOLs can be further subdivided into diffractive and refractive types.
Diffractive IOLs, such as Tecnis and ReSTOR, create two distinct images at near and far distances. ReSTOR was the first diffractive lens approved by the FDA in 2005. Its mechanism of action is based on apodization, in which a near-dominant central area is surrounded by 12 concentric rings of decreasing height, resulting in diffraction of light at both near and far distances. The Tecnis diffractive IOL is an acrylic lens with an aspheric anterior surface and a posterior surface featuring diffractive rings that focus both close and distant light, regardless of pupil size.
Diffractive IOLS are typically less limited by pupillary diameter, but can result in poorer intermediate vision.
Refractive IOLs such as ReZoom and Array function by creating multiple focal points that allow for viewing at all distances. The Array zonal progressive silicone IOL consists of five concentric zones, alternating between distance- and near-dominant zones. The ReZoom IOL is a second-generation refractive IOL that enhances certain aspects of the Array design, including enlargement of the second and third zones, reduction of the fourth and fifth zones, and an aspheric transition between zones, thereby reducing visual disturbances.
While refractive IOLs produce reasonable quality distance, intermediate, and near vision, they are limited by pupillary diameter because of the zonal design of the lens.
Accommodative lens implants
Currently, the only accommodative lens implant approved by the FDA is the Crystalens IOL, a 4.5 mm optic with two haptic plates and four polyimide loops that help secure it in place within the capsular bag. Its placement within the capsular bag allows it to simulate the natural accommodative process in the eye by changing power in response to ciliary muscle contraction.
Is there anything better?
For many cataract patients, however, the possibility of glare, halos, and other visual quality issues has led them to shy away from multifocal lenses and opt for monofocal options.
There are, however, some lenses that aim to bridge the gap between multifocals and monofocals, allowing for more vision at different distances while minimizing visual side effects. The AMO Symfony lens is a recent example of this. This lens expands the depth of field while also addressing chromatic aberration that can decrease acuity. The Symfony uses diffractive optics to both improve the quality of vision from the lens and expand the range of distances at which the lens can adequately focus.
What about the cost?
Medicare and most other health insurance policies cover the basic costs of cataract surgery. However, presbyopia-correcting IOLs are not considered medically necessary by either. Typically, Medicare and health insurance companies will only cover the cost of a monofocal intraocular lens implant. Presbyopia-correcting IOLs are considered elective luxuries and are not covered by insurance.
The cost of presbyopia-correcting lens implants is higher because these specialized lenses cost more for companies to develop and produce, and because advanced surgical skills are often required to implant them correctly. Extra care must be taken with these lenses to make sure you receive the exact right prescription (IOL power calculation) for your eyes, which may require additional and advanced testing before surgery.
For a favorable outcome with a presbyopia-correcting lens implant, ensure your surgeon is dedicated to the necessary IOL technology and has received appropriate training in performing cataract surgery with these premium intraocular lenses. Be sure to thoroughly discuss the advantages and risks associated with presbyopia-correcting IOLs with your cataract surgeon at your preoperative exam and consultation.
