In today’s contact lens market, more multifocal options exist than ever before to address our presbyopic contact lens wearers’ visual and comfort needs. In the last several years, parameter and modality options have increased to include several new daily disposable options, and power ranges have expanded sphere power choices and even offer multifocal toric powers.
Prescribing trends show that eyecare providers (ECPs) are recognizing the benefits multifocal contact lens options have over monovision modalities,1,2 and multifocal options have increased to overtake the market when it comes to presbyopic contact lens prescribing.3
These advances are great news for presbyopic contact lens wearers. As prescribing options increase, however, ECPs might feel overwhelmed with options and unsure how to determine what brand or modality is best for each individual patient.
Making a great multifocal lens choice starts with understanding how soft multifocal contact lenses work and understanding the nuances of the designs that are available. Below, let’s review the optics of soft multifocals and highlight features that lead to presbyopic visual success.
How does a multifocal work?
You might remember learning about several different types of multifocal optical designs in the past. Most modern soft multifocal designs, however, use aspheric optics, which are sometimes described as simultaneous vision designs. These lens designs manipulate aspheric aberrations to increase depth of focus and “pseudo-accommodate” for the wearer.4-6
This essentially means that a gradient of power is distributed concentrically around the lens. To simplify this concept, think about a spectacle progressive addition lens (PAL). A PAL has distance power at the top, and the power gradually transitions to intermediate and near as the eye moves down the lens.
A soft multifocal contact lens has a similar power gradient, but it is oriented circumferentially around the lens to allow the different powers to enter the pupil from all angles. All soft multifocal lenses have what is known as a power profile. This is the distribution of power from the center of the lens optic to the periphery.
Understanding power profiles in multifocal contact lenses
This power profile represents the distance to near ratio of the design and depends on the size of the aperture (in this case, the pupil) in order to allow that power ratio to enter the eye.7,8
With this concentric power gradient, a multifocal contact lens has the option of having the distance or near power in the center of the lens. Most presbyopic multifocals on the market have a “center near” design. This type of design works in concert with the physiology of the pupil as it constricts during near viewing.
Figure 1: Illustration of the center near design in multifocal contact lenses.
Figure 1: Courtesy of Johnson & Johnson Vision.
When the eyes focus at near, pupil size decreases.9 If a multifocal has center distance optics, the portion of the lens with near power may not be able to get into the pupil, and the near vision will suffer. With a center near design, however, the near power is situated within the central pupil.
Even in a miotic pupil state, the near power can easily enter the eye and provide clear near vision. When the wearer changes focus to the distance, their pupil size increases, and the more peripheral distance portion of the lens can then provide good distance vision. So, center near designs are most appropriate for presbyopic multifocal wearers.
Pupil size matters
A good visual result with a multifocal contact lens is reliant on light passing through each power portion of the lens (near, intermediate, and distance) and entering the eye in an optimal ratio to allow for clear vision at all distances.
Several factors may influence if light rays from all power portions of a multifocal contact lens can enter the eye. Lens centration, for instance, can affect this power ratio. Ultimately, however, the pupil is the primary regulator of what light rays enter the eye once they pass through the contact lens and the cornea and, most importantly, how a patient perceives vision at all distances.4,10,11,12
Pupil size is dynamic. Pupils get larger in dim light and smaller in brightly lit environments.10 It would be difficult for a lens design to account for these minute-by-minute pupil size changes, but a lens design can consider broader, age, and anatomical facts and features regarding pupil size.12,13
How does pupil size impact multifocal contact lenses?
For instance, we know that pupil size tends to decrease with age.12,13 A 75-year-old patient will have notably smaller pupil sizes than a 35-year-old patient. As well, myopic eyes tend to have larger pupil diameters than hyperopic eyes.12,13 A 9-diopter myopic eye will be expected to have a markedly larger pupil than a 6-diopter hyperopic eye.
These facts mean that older patients with hyperopic powers have smaller pupils than younger patients with myopic prescriptions. Or, more specifically, presbyopes needing higher add powers with hyperopic prescriptions have smaller pupils than patients needing lower add powers with myopic prescriptions.
Pupil size, therefore, should be carefully considered when choosing a multifocal. Each individual presbyopic patient could benefit from a uniquely sized power profile designed to anticipate pupil size based on their distance and add power needs.
Improve outcomes with an optimized option
Most multifocals on the market today are manufactured with a single “one-size-fits-all” power profile per add. This means that an eye with a pupil size smaller than the design intent of the power profile may be flooded with near power only, making distance vision blurry.
Conversely, an eye with a pupil size much larger than the power profile of the lens may be flooded with peripheral distance light rays, making near vision blurry. If you want to enhance your multifocal contact lens fitting, however, there are options that adjust the lens power profile to account for anticipated age and refractive error-dependent pupil size factors.
Johnson & Johnson has modernized multifocal technology across all of their multifocal lenses to feature a Pupil Optimized Design.
How does the Pupil Optimized Design work?
This innovative design creates a unique series of power profiles that change in relation to the distance and add power of the lens. The power profile of every lens in the fitting set is different from the one before or after it.
This nearly-custom lens design means that the patient is most likely to achieve that ideal ratio of distance, intermediate, and near power entering their unique pupil at the same time, resulting in optimal vision at all distances.
A Pupil Optimized Design is seen in all Johnson & Johnson presbyopic products (1-Day Acuvue Oasys MAX, 1-Day Acuvue Moist, and Acuvue Oasys Multifocal), and can lead to a more effective and efficient fitting process.
Because the power profile of the contact lens is optimally matched to the pupil size of the patient, the first trial pair is more likely to provide good initial vision at all distances, leading to an easier, more enjoyable adaptation process for the patient and minimal troubleshooting, chair time, and follow-up visits.
Final thoughts
Understanding the optical nuance of multifocal contact lens design and how it varies across products can help ECPs choose a multifocal that will best address their presbyopic patients’ needs.
Products that consider pupil size in relation to the optical design are most likely to deliver good vision at all distances with the first trial pair, making the fitting process easier for the patient and the ECP.
