The add powers are unique, and understanding them requires an understanding of the lens's optics. "The PureVision Multifocal uses aspheric optic technology over the entire optic zone of the lens," Dr. Pier says. "We've increased the wearer's depth of focus, instead of refocusing the light in different powers as you would in a bifocal or trifocal. 

The lens allows the patient to see at various distances without a separate zone-of-focus change, meaning there's no ghosting, shadows or doubling of images that we were used to having with more traditional styles of bifocal or trifocals in spectacles or early contact lenses. The change of focus starts in the center of the lens, and then moves out toward the periphery, gradually changing the curvature of the anterior surface, making it aspheric instead of spheric. 

"We use these aspherics as we would use add powers, such as +1, +1.5, etc., but because they're fully translatable, it's not an individual focus," explains Dr. Pier. "So, we've separated it into two primary aspherics, a low add and a high. The low add is less aspheric and the high add is more. This has worked well for the lens, since we no longer have to worry about whether a patient is an early presbyope or a little bit more advanced; we can cover more area with less add power by virtue of using these aspherics, and we don't have to have four or five adds. This can be easier for the patient because he's able to wear those lenses longer without having to go to a different focal power, as many presbyopes do as they progress from early presbyopia to mid-presbyopia and eventually absolute presbyopia." 

In terms of fitting the lens, Dr. Pier says the company counsels doctors to try to fit toward subjective refraction and spectacle add based on whether the patient is an emerging or mature presbyope. "We use the low add for emerging presbyopes, and the high add for mature," he says. "Mixing adds might be a secondary option if the initial fit wasn't performing correctly, but balancing the eyes for binocularity is what we're looking for." 

The lens also has a rounded, polished edge that the company says makes for a better interaction with the limbal conjunctival surface.

• SofLens Multifocal.  This is composed of HEMA material, the same type of polymacon material B+L uses in its other SofLens products. Dr. Pier says that, though the SofLens optics are primarily of the same design as those in the PureVision Multifocal, the latter has recent design upgrades that were possible as the company "got more technologically capable with manufacturing." 

• SofLens Multifocal . This is composed of HEMA material, the same type of polymacon material B+L uses in its other SofLens products. Dr. Pier says that, though the SofLens optics are primarily of the same design as those in the PureVision Multifocal, the latter has recent design upgrades that were possible as the company "got more technologically capable with manufacturing." 

CIBA Vision offers Air Optix Multifocal Aqua lenses for monthly replacement and Focus Dailies Progressives for daily disposable wear. 

• Air Optix Multifocal Aqua. This is a silicone hydrogel contact lens that comes in sphere powers of +6 to -10 D in 0.25-D steps, with one of three add choices: low; medium and high. The company says that the low add works well for patients who need up to +1.25 D of spectacle add; the medium is recommended for those who need from +1.5 to 2 D of add power; and the high is for +2.25 to +2.5 D of add. The near zone of the lens is in the center. It has a base curve of 8.6 and a diameter of 14.2 mm. 

Dwight Akerman, OD, director of professional affairs and programs for CIBA Vision's North America operations, says the lens is popular for a couple of reasons: "First, the design itself is a benefit," he says. "It's a bi-aspheric design, with the back and front being aspheric. The specific design is proprietary, but it allows us to provide patients with an increased depth of focus. In essence, the AO offsets the loss of accommodation by extending the depth of focus and allows presbyopes to have normal binocular vision that monovision doesn't provide. We fit both eyes fully corrected for near and for distance. The next reason the lens works well is the Aqua Moisture System, which consists of the silicone hydrogel material that transmits five times as much oxygen as HEMA, a plasma surface treatment and a moisture agent in the packaging solution that binds to the lens surface and creates a silky layer to enhance wearing comfort." 

Dr. Akerman says that even though in the past established presbyopes with high add requirements often had to compromise distance vision with multifocal contact lenses, wearers are having a good experience with the AO Multifocal Aqua. "In studies of our sales, the medium add is the most frequently utilized add, but the high add is actually second," he says. "We're pleased with that, because it means our lens is working well for these high-add patients."

• Focus Dailies Progressives. This is CIBA Vision's daily disposable lens for the presbyope, composed of nelfilcon A. Dr. Akerman says it doesn't have the flexibility of the three add powers as the AO lens does, and instead has what amounts to one add power. "It's a progressive add power that has up to 3 D of add in an aspheric, center-near design," he says. "The add power changes with each lens power. The add stays the same across the power range with the AO lenses, but with the Focus Dailies it changes with each sphere power. So an add for a -3 D Focus Daily lens will be different than that for a -2.5 D lens." It's available in +5 to -6 D, and has a base curve of 8.6 and a diameter of 13.8 mm. "The great thing about dailies is there's no deposition to speak of," says Dr. Akerman. "There's no need for lens solutions and no risk of allergic or toxic reactions." 

CooperVision
CooperVision offers several lens-es for a variety of presbyopes: the Proclear Multifocal; Proclear EP (for early presbyopes); Proclear Multifocal Toric and the Frequency 55 Multifocal. 

• Proclear line of multifocals. These are all made of omafilcon A, a material that the company says retains moisture throughout its wearing cycle. "It's the only lens on the market with an FDA labeling indication for improved comfort for patients with dry eye," avers Doug Brayer, CooperVision's director of marketing. "This means a lot for the presbyopic patient, who is more mature and often experiences contact lens dryness." The Proclear Multifocal lenses use an optical system the company calls Balanced Progressive Technology. This design involves putting a different lens on each eye, but having them work binocularly to give the patient good vision. "We have a D lens for the dominant eye that's center-distance with intermediate and near vision in the periphery," says Mr. Brayer. "And then we have an N lens that's center-near with distance and intermediate vision in the periphery. So, it provides more options for the prescribing practitioner to get a good fit." Though Mr. Brayer says patients don't necessarily experience problems with having two different lenses in their eyes, there may be instances where alterations have to be made after the initial wearing. "There are many cases of patients with greater near vision needs in which the practitioner might prescribe two N lenses," he says. "This works because even though they're N lenses with the near correction in the center, they also have distance and intermediate correction in them, as well. For lower presbyopes, we often find two D lens fittings to be more effective." The add powers start at +1 D and go up to +2.5 D. The sphere powers run from +6 to -8 D, with a base curve of 8.7. 

There's also an XR lens with adds up to +4 D and a spherical range from +20 to -20 D. The Proclear Multifocal Toric can accommodate patients with cylinder values of up to -5.75 D, spheres from +20 to -20, adds up to +4 and round-the-clock astigmatic axes in 5-degree steps. The toric has two base curves: 8.4 and 8.8. 

The Proclear EP lens is for emerging presbyopes, and just has one low add power, +1.25, rather than having separate D and N designs like the other lenses in the line. Its center is set for distance vision. "With fewer variables, the EP is an easy fit for a practitioner," says Mr. Brayer. "And it gives the patients just enough near vision to help them without having them sacrifice distance correction." 

• Frequency 55 Multifocal. This lens has the same approach to correction as the Proclear line, using N and D lenses, but is made of a different material, methafilcon A. Mr. Brayer says that while this is a good material, it doesn't offer the benefits of omafilcon A, such as the FDA labeling indication and the overall comfort in wearing. 

Vistakon/Johnson & Johnson
Vistakon has two options for presbyopes, a multifocal Acuvue Oasys for Presbyopia and the Acuvue Bifocal.

• Acuvue Oasys for Presbyopia. The Oasys for Presbyopia is a soft, lubricated silicone hydrogel made of cenifilcon A. "The material has good oxygen-delivering capabilities and doesn't need a surface treatment," says Sheila Hickson-Curran, MCOptom, Johnson & Johnson's director of medical affairs. "The lens also contains Hydraclear Plus, a built-in wetting agent." The lens comes in a spherical range of +6 to -9 D, with adds from +0.75 to +2.5 D. The base curve is 8.4 and the diameter is 14.3 mm. It's for patients with no more than 0.75 D of astigmatism. 

"The optics, located on the front surface, are simultaneous vision op--tics," explains Dr. Hickson-Curran. "This technology combines a concentric ring type of optic with an aspheric optic. We use a zonal aspheric optic with a central zone that's biased toward distance, with the next zone being aspheric but biased toward near vision." Dr. Hickson-Curran says the lens's back is aspheric in order to optimize lens centration. "The mechanics of the back curve help maintain the fidelity of the optics on the front surface," she says. "To understand how this helps, consider what would happen if you were to put a 'drapey' contact lens on a cornea. The lens would drape to the particular shape of the cornea and transmit some of that shape to the front surface, affecting the optics. In a multifocal lens the optics are pretty complex and this shape change could alter its effectiveness." 

• Acuvue Bifocal contact lenses. The Acuvue Bifocal is composed of etafilcon A. It's available in sphere powers from +6 to -9 D, with four add powers (+1, +1.5, +2 and +2.5). Its base curve is 8.5, and its diameter is 14.2 mm. "A lot of doctors have found the Acuvue Bifocal to be a good choice for hyperopic presbyopes," says Dr. Hickson-Curran. "The way the optics are set up, they work very well on the plus side of the spectrum. It's always been good for near vision, but sometimes patients have had to compromise their distance vision—myopes aren't going to do that." 

The optics are a concentric-ring design, with distance in the center and five zones moving out from the center and alternating distance and near. 

Though presbyopia can be a moving target as your patients age, the makers of all these advanced multifocal contact lenses believe they can help you hit the target more accurately, both now and in the future.  REVIEW