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KEEPING UP WITH THE PRESBYOPES

As the population of presbyopes has grown, so have their multifocal contact lens options.

There has never been a better time to care for presbyopic patients who desire contact lenses. With the wide range of products and parameters available today, we can offer emerging-to-advanced presbyopes who have nearly every eye shape and refractive error an opportunity to decrease their dependency on additional eyeglasses for reading or computer use.

The presbyopic lane of the contact lens market plays a big part in the success and progress of the industry as a whole. Presbyopia drives manufacturers to develop materials that have higher oxygen transmission, softer modulus, and better surface wettability to ensure comfortable lens wear for this aging population. It also challenges manufacturers to continue to improve the optical performance of their designs to enhance the visual experience for presbyopes who have a wide range of vision demands.

In this article, I discuss current—primarily soft—lens designs for presbyopes, fitting techniques, and troubleshooting as well as some of the latest technological advancements in the multifocal contact lens arena.

ANSWERING THE QUESTION “AM I A CANDIDATE?”

Many presbyopic patients have been told in the past that they are not candidates for multifocal contact lenses. With the expansion of lens designs and parameters in the last several years, however, the answer to the question “Am I a candidate?” has likely changed for many of these patients.

The best candidates for multifocal contact lenses are current lens wearers. They can already report on their lens comfort and function, and practitioners can immediately evaluate on-eye lens performance. New contact lens wearers require a few extra steps—determining which lens fits well and confirming the distance prescription—before we can introduce multifocal optics. In general, there is a good multifocal contact lens option for most patients.

Reviewing lens performance capabilities and managing patients’ expectations are important aspects of the conversation when determining candidacy for multifocal contact lenses. Practitioners must make it clear that these lenses produce images on the retina differently than progressive addition spectacle lenses do and that the processing of the images requires adaptation.

When describing how a multifocal contact lens works to patients, I explain that both near and far optics are placed in the center of the lens, and the lens wearer sees through both sets of optics at the same time. The brain selects the clearer image and learns to ignore the other one.

Images produced through most multifocal contact lenses are described as simultaneous vision or simultaneous images, as the goal is to place both near and far optics in the pupillary area for all gaze positions.1 Initially, contrast is reduced in exchange for increased depth of focus, but contrast improves with time.2,3 Some researchers suggest that clinicians prepare patients for ghosting or shadowing of vision during the first seven days of multifocal lens wear4 and that lenses should be worn for 15 days prior to a complete vision reassessment to adjust lenses.5 Encourage patients to allow sufficient time for the visual system to adapt, as this is essential to success with multifocal contact lenses.

ANATOMIC ASSESSMENTS

Before starting a contact lens fitting with a new presbyopic patient, ensure that his or her vision, ocular surface, and lid dynamics can support contact lens wear. Ocular surface changes occur as people age, so ensuring the quality of the tear layer and meibomian gland function will rule out dryness as a reason for decreased vision quality as the contact lens fitting progresses.

Eyelid dynamics also play a role in a successful contact lens fitting. While excessive eyelid laxity would require surgical intervention to improve function, practitioners should still note poor apposition or poor tear spreading on the eye and watch for a dry or decentered lens as a result.

Screening for lenticular opacities is also an important step to identify the potential for decreased visual acuity and vision quality that cannot be addressed by spectacle or contact lens correction. Asking patients about their vision in moderate-to-dim lighting and about their comfort while driving at night can reveal the effect of cataracts on current visual function. A fundus examination to assess macular health will complete the screening.

INITIAL CONSIDERATIONS

When selecting a multifocal lens design, consider the wearing schedule that a patient desires and what he or she would like to see while wearing the lenses. For example, if a patient is interested in part-time lens wear, GP lenses are not the best option unless the patient is already wearing GP lenses. Provided that the appropriate parameters are available, daily disposable multifocal lenses are a better choice for part-time lens wear.

The desired acuity will also influence your lens choice, particularly when working with custom soft or GP lens designs. Multifocal contact lens designs can be categorized as simultaneous vision or alternating vision, also known as translating lenses.

Aspheric Multifocals Aspheric multifocal lens designs are in the simultaneous vision category. They feature a gradual change in surface curvature to create a change in power from the center to the periphery (Figure 1A).6 Light rays from the power distribution across the lens surface enter the pupil at the same time, creating multiple images on the retina. The change in power increases depth of focus, providing functional vision at near, intermediate, and far distances. The visual system then adapts to select and process the clearest image.7

Figure 1. Examples of how optics can be distributed across a multifocal contact lens.
Images courtesy of allaboutvision.com

A concentric multifocal is a lesser-utilized simultaneous vision design that consists of specific curves rather than a smooth blend (Figure 1B). Some designs in this category combine aspheric and concentric lens features.

Aspheric multifocal lenses offer several benefits. First, these lenses are comfortable. If a patient is wearing a single-vision lens with good comfort, then he or she should also experience good comfort in an aspheric multifocal lens. This makes aspheric multifocal lenses an adequate choice for most presbyopes. It also often helps reduce chair time, as patients are already wearing a well-fitting lens most of the time, which allows practitioners to focus on the lens optics.

Aspheric multifocal lenses are pupil-size-dependent, and their performance may be reduced for patients who have larger- or smaller-than-average pupils. Custom soft and GP lenses have adaptable zone sizes to make the optical power distribution more proportionate to the pupil size.

A challenge for some new multifocal wearers is the perception of the simultaneous images. Some patients will describe a subtle doubling or ghosting of the image. This usually subsides with adaptation, and most patients are satisfied with the performance of their aspheric multifocal lenses in adequate lighting.

Translating Multifocals Translating or alternating vision multifocal lens designs separate the lens power (Figure 1C), with the line of sight alternating between the distance and near powers as the eye moves behind the contact lens. This lens design is exclusive to corneal GP lenses at this time. It is custom-made based on measurements of the eye, and it uses eyelid interaction to maximize lens performance.

Because a translating lens separates lens powers rather than blending them, a significant benefit is the quality of vision that patients can achieve. While the optics require less adaptation, patients may need to adapt to the lens comfort. Most corneal GPs interact with the upper eyelid for lens positioning, but translating multifocal GP lenses interact with the lower lid, which creates a different sensation even for habitual GP lens wearers.

THE WORKUP

Fitting a multifocal contact lens is similar to fitting any type of contact lens, with just a few modifications—particularly if you are considering a custom-designed multifocal lens. Begin with a thorough contact lens history to determine whether patients have worn contact lenses successfully or whether they have had vision or comfort issues in the past. Gaining an understanding of overall ocular comfort with respect to dryness or ocular allergies is also important.

Next, determine the refractive error with the add and the best-corrected visual acuity to ensure that adequate vision can be achieved with multifocal optics. Best distance acuity may decrease for patients who have advanced irregular corneal conditions or mild-to-moderate cataracts because of aberrations and light scatter. I also recommend measuring pupil size in various light conditions, taking keratometry readings, and determining eye dominance. We can use pupil size to select the optical multifocal design or upgrade to custom lenses. Eye dominance will help us modify add powers or zone sizes to maximize visual function. Corneal topography can be helpful in cases of moderate-to-high amounts of astigmatism to help determine how to maximize rotational stability.

FITTING (IN) MULTIFOCALS DURING A BUSY DAY

Multifocal contact lenses can be a challenge for patients and practitioners. For patients, it can take some time and lens changes before the desired vision is achieved. For practitioners, that means extra visits and chair time, which can make it difficult to stay motivated to fit these lenses. It’s tempting to switch from brand to brand if initial outcomes are less than expected and to conclude that a patient is not a candidate for multifocal contact lenses when nothing is successful. To optimize the patients’ experience and the practitioners’ chair time, try these tips from beyond the fitting guides:

  • Aim for a well-fitting lens. Making predictable vision changes is difficult when a lens is decentered (Figure 2) or moving excessively. Select lenses that are sufficient in diameter and movement, and when working with toric optics, make sure that the lenses are rotationally stable. A well-fitting lens is essential to success.

    Figure 2. This image shows the temporal decentration of a soft contact lens. Significant decentering can affect optical performance and lens comfort.
    Image courtesy of Matt Lampa, OD

  • Tell patients what they can expect visually while the first lens is settling. Acknowledge that vision may not be “perfect” right away, and remind patients of the adaptation period and of your ability to make changes, if needed. This conversation reassures patients, builds their confidence in the process, and saves practitioners time in troubleshooting.
  • Use real-life vision challenges. Having patients view their cell phones for near targets and look out a window for distance can be more predictive of success compared to using an acuity chart. (Note: Distance acuity with multifocal lenses should be recorded in patients’ charts for medical-legal purposes and to ensure driving safety.)
  • Use loose lenses to assess lens power. The phoropter can change pupil size, affect binocular vision status, and make it more difficult to judge a patient’s responses. Always present a plus-power loose lens first to rule out potential over-minusing. Then, optimize distance vision in the dominant eye before addressing near acuity.
  • Don’t confuse increased contrast for increased acuity. The trade-off for increased depth of focus is decreased contrast sensitivity.8 Most of the time, patients will accept minus power if it is presented to them. Sometimes it’s needed, but oftentimes they are appreciating the increased contrast.
  • Remember that adaptation can take two weeks. Remind patients that their vision quality will improve if they wear the diagnostic lenses. The goal of the first visit is to get patients to a functional place with the lenses, then reassess at a follow-up visit.

TROUBLESHOOTING

According to research, insufficient vision quality is one of the main reasons why patients stop wearing multifocal contact lenses.9 Patients report a range of symptoms including compromised acuity, reduced stereoacuity, ghost images, haloes, and vision fluctuation.10 Practitioners have tools and options available to them if their patients are less than satisfied with their multifocal lenses.

For patients wearing mass-produced soft multifocal lenses, first address the fit to ensure that you can continue working with the same brand. We have minimal to no control over the lens diameter and base curve; therefore, our only option when the fit is not acceptable is to switch lens designs. Evaluate the lens with the slit lamp for adequate centering, quick and limited movements on blink, and sufficient drape over the limbus. Also, look for deposits and poor tear spreading on the lens surface.

If the fit appears adequate, evaluate the lens power. Use loose lenses to determine power adjustments for best acuities at distance and near. If the lens power is significantly different from the manifest refraction, consider a brand or design change. Patients may be sensitive to the optical design or the zone size; the lens material may not agree with their tear layer or eyelids; or the lens may not be centering well, and patients cannot utilize the optics.

Another tip from the pros is to select an appropriate lens design based on a patient’s pupil size. Although larger pupils are less likely in the presbyopic population, the perception of glare and haloes is more common when the pupil is greater than 5.0mm in normal room illumination.10 You may observe this in younger presbyopes when in dimmer light conditions.11 A concentric ring design can improve vision quality for these patients.11 Conversely, patients who have small pupils will need a design with a compact power distribution in the center, so that all powers, near to far, can enter the pupil. These patients may need an add power for the intermediate distance in spectacles, but with multifocal contact lenses, a high add may perform best.

If you are using a custom soft multifocal, a consultant can guide your next steps. He or she may suggest switching the optical design from near-center to distance-center or changing the zone size to make the optics more accessible to the pupil. Another suggestion might be to change the diameter or base curve to improve the lens stability and centration.

TECHNOLOGICAL ADVANCEMENTS

Discomfort related to contact lens dryness is the primary reason why patients stop wearing their contact lenses.12 In one study, more than 40% of previous contact lens wearers cited dryness as their reason to discontinue use of their lenses.13

Until recently, practitioners had to rely on changing lens materials or prescribing pharmaceutical agents to try to improve the wearing experience for their patients. We now have a new option to consider. A polyethylene glycol-based coating that is bonded to the surface of a contact lens attracts water and improves deposit resistance on GP and soft contact lenses. The treatment increases lens surface lubricity and aims to increase daily wearing time, according to the manufacturer. As the eyes become increasingly dry with age, this technology may help reduce contact lens dropout related to lens discomfort. It is available on certain soft, hybrid, and GP lenses.

Dissatisfaction with quality of vision is another well-documented reason why patients stop wearing multifocal contact lenses.10,15 One technological advancement in multifocal lenses mirrors a surgical approach to improve visual outcomes in patients undergoing refractive surgery; surgeons are decentering laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) treatments over the line of sight rather than over the center of the pupil to reduce postoperative glare and haloes.16 The line of sight is located superior nasal to the pupil center, and the difference between these two landmarks is defined as angle kappa. Decentering the optics of multifocal contact lenses over the line of sight is a new approach that is showing improvement in visual performance compared to traditional multifocals that have centered optics (Figure 3).17 The main improvements are fewer reports of haloes and double vision or ghosting. Decentered optics are available in soft and scleral GP contact lenses.

Figure 3. Decentered optics in multifocal lenses are a technological advancement improving the visual experience for lens wearers.
Image courtesy of Matt Lampa, OD

THE BOTTOM LINE

The development of high-quality multifocal contact lenses has grown exponentially in the past decade. As a result, our outcomes are better than ever with the use of appropriate lens designs, guidance from consultants, and the latest technologies.

Today’s presbyopes are tech-savvy, active people who aren’t planning to slow down anytime soon. Thankfully, our multifocal contact lens designs can keep up with them. CLS

REFERENCES

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  2. Plakitsi A, Charman WN. Comparison of the depths of focus with the naked eye and with three types of presbyopic contact lens correction. J Br Contact Lens Assoc. 1995;18(4):119-125.
  3. Montés-Micó R, Alió JL. Distance and near contrast sensitivity function after multifocal intraocular lens implantation. J Cataract Refract Surg. 2003 Apr;29:703-711.
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  14. Richdale K, Mitchell GL, Zadnik K. Comparison of multifocal and monovision soft contact lens corrections in patients with low-astigmatic presbyopia. Optom Vis Sci. 2006 May;83:266-273.
  15. Moshifar M, Hoggan R, Muthappan V. Angle Kappa and its importance in refractive surgery. Oman J Ophthalmol. 2013 Sep;6:151-158.
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