Success with multifocal contact lenses requires the application of two complementary skill sets: science and art. Science, in essence, teaches us how things work, while art is our approach to implementing the science. Here’s how to combine these two aspects of contact lens fitting so that they add up to multifocal contact lens success.

SCIENCE WEIGHS IN ON MULTIFOCALS VERSUS MONOVISION

Numerous studies comparing the performance of multifocals to monovision have reported that approximately seven out of 10 patients prefer multifocal contact lens correction.^1-3 These same studies indicated that the most challenging visual scenario that patients encounter while wearing multifocal contact lenses is performing near tasks in dim light.

Share this science with your patients when you embark on multifocal fitting. The high preference rate for multifocal contact lenses demonstrated in these studies will give you confidence that you’re doing the right thing for your patients. In addition, the awareness of near vision performance in low light gives you the opportunity to arm your patients with strategies and tools, such as the use of additional light and/or magnification, to manage this issue. A subsequent study revealed subjective preferences for multifocals over monovision for driving at night, watching television, and working on a computer, even though objective findings such as visual acuity measurements may be better with monovision.⁴

How to put this science into action? Although visual acuity measurements can be helpful, when weighing whether a lens modification is indicated, let patients’ subjective feedback be your primary guide.

INITIAL CONSIDERATIONS

Start the Multifocal Conversation Early Science and clinical experience tell us that the higher the add power of a multifocal contact lens, the higher the likelihood of disturbance to distance vision.^5,6 In other words, success tends to be easier to achieve when patients require low adds. Our advice? Fit your patients early. Better yet, share what you know is coming and inform incipient presbyopes that their near vision will soon begin to drop off. This no-surprise approach encourages patients to seek you out for help—rather than dropping out—when they begin to experience visual strain with near tasks.

Be Proactive Multiple studies have demonstrated how important it is to be proactive in recommending contact lenses to new patients, particularly presbyopes.^7,8 In one study, patients were 2.5 times more likely to be fitted when contact lenses were proactively recommended compared to when they were not.⁷ When this study was repeated with presbyopia-only patients, more than two times the number of patients were fitted with contact lenses when they were proactively recommended.⁸

The Role of Astigmatism in Multifocal Fitting Science tells us that low amounts (0.75D to 1.00D) of uncorrected astigmatism can result in a one-line reduction in visual acuity under mesopic conditions.⁹ From this, we can conclude that astigmatic errors of about 0.75D or more must be corrected to achieve success with multifocal contact lens fitting. Fortunately, many multifocal contact lens designs achieve this effectively.

GP MULTIFOCALS

The hallmark of GP contact lenses—in any form and for any type of patient—is quality of vision. This is particularly true for emerging presbyopic patients who may take for granted that they can see well at all distances until they start noticing blur at near and possibly at other distances if they’re not well corrected or satisfied with a soft lens. Studies comparing high- and low-contrast acuity as well as contrast sensitivity indicate that GP multifocal wearers performed at the highest level, followed by soft multifocal wearers and, finally, monovision wearers.¹⁰ Several different types and designs of GP multifocal lenses are available to provide your patients with this superior level of vision quality. Table 1 provides a quick guide to GP multifocal selection.

Corneal Multifocal Designs Corneal GP multifocals are available in either aspheric or translating designs.

• Aspheric Lenses Aspheric designs have become a popular form of correction as scientific advancements have been translated into technological improvements. Today’s lenses have better polished surfaces and can be manufactured to incorporate high add powers. In addition, many designs are completely or predominantly front-surface aspheric, with the add power on the front. This allows the back surface to be fitted similarly to a spherical lens, thus encouraging empirical fitting. Typically, the first GP lens worn with empirical fitting provides very good vision and likely reduces subjective concerns about lens awareness. In fact, 75% of practitioners fit their aspheric GP multifocal patients empirically.¹¹

Most presbyopic patients can be fitted with aspheric designs, because good-quality vision can be achieved at all distances. Most have a center-distance design, and the center zone can typically be reduced to achieve a higher add for patients who have advanced presbyopia or small pupils.¹² With the add on the front surface, a reverse curve can be incorporated on the back surface, which is ideal for post-refractive-surgery patients who have an oblate corneal shape and are not satisfied with other types of vision correction. This is an important option to mention to patients initially. If they decide to go with soft multifocal lenses or monovision but are not satisfied with their vision, they’ll know that they have other options.

• Segmented Translating Lenses These lenses often elicit an emphatic “Wow!” from patients when they first experience their quality of vision. When properly fitted, these lenses translate or shift superiorly on downward gaze for near work, enabling patients to view through the near optics in the inferior region of the lens.

Because these lenses include a segment (seg) line (or two) and are prism-ballasted to sit at or near the lower lid margin, diagnostic fitting is recommended. If diagnostic fitting is not possible and the lower eyelid is tangent to the lower limbus, a seg height that is 1mm below the geometric center of the lens will often function well. For example, for a 10mm diameter lens, the geometric center is 5mm, so you would specify a 4mm seg height.

Translating lenses are ideal for patients who want uninterrupted vision at distance and at near. Of course, as much of today’s work is at an intermediate distance, every laboratory has one or more designs that incorporate an intermediate correction, using either a distinct separation (i.e., executive or upswept seg) or an aspheric intermediate zone.

To achieve inferior centration, these lenses are often fitted with a base curve radius slightly flatter than K, which encourages downward movement; combining this with a thin upper edge minimizes the likelihood that the lens will be picked up too superiorly and positioned in front of the pupil during straight-ahead gaze. The contoured lower edge of these prism-ballasted designs—together with limited movement with the blink—results in better initial comfort for segmented, translating (as well as aspheric) lenses compared to conventional spherical corneal GP lenses, which typically move more on the eye with the blink.¹³

Scleral Multifocal Designs The availability of scleral multifocal lens designs is increasing, as every laboratory now has at least one such design. Scleral multifocals are ideal for emerging presbyopes who currently wear scleral lenses, and they are one of the few, if not the only, contact lens options for presbyopes who have moderate-to-severe dry eye disease. Patients who have mildly irregular corneas (i.e., absence of scarring) and patients who have undergone refractive surgery are also candidates for scleral multifocals.

Most scleral multifocal designs are center-near, as they don’t translate with downward gaze; however, the GP optics typically provide satisfactory vision at distance and excellent intermediate and near vision. They are relatively simple to fit. Often, all that’s necessary to fit a patient currently wearing scleral lenses is to provide the add power and possibly the pupil size to the laboratory. Otherwise, patients can be fitted with a conventional scleral lens, and the best-fit parameters along with add power and pupil size can be sent to the laboratory.

Scleral multifocal designs are becoming more customizable by the day. Back-surface toric and even quadrant-specific haptics assure good lens-to-sclera alignment. We know that scleral lenses tend to decenter inferior-temporally because of the elevated nasal sclera combined with the mass of the lens. Science indicates that decentering the optics superior-nasally so that the center of the center-near zone aligns with the visual axis improves the visual response.¹⁴ Over-topography can be used for this purpose,¹⁵ and for an optimum visual response, the decentration should be measured for each individual patient.¹⁶

Hybrid Multifocal Designs Hybrid multifocal designs have also improved in recent years. The latest generation of lenses designed for regular corneas has a 14.5mm diameter, with a hyper-Dk (130) GP center and an 84Dk silicone hydrogel skirt. The primary design is center-near and is available in three progressive add powers. The manufacturer has also introduced a progressive center-distance design for emerging presbyopes that has an adjustable center-distance zone ranging from 1.8mm to 4mm.

The most recent introduction to this line of presbyopia-correcting lenses, SynergEyes ID Multifocal EDOF, employs extended depth of focus (EDOF) optics and is custom-designed based on keratometry, horizontal visible iris diameter, and refractive error. The online SynergEyes Empirical Lens Calculator can be used to determine the appropriate design as well as the specific lens parameters for each individual patient.

The Bottom Line on GP Multifocals In our opinion, the primary resources for successful GP multifocal fitting are the laboratory consultants. These design and fitting experts are aware of current science and technology as it pertains to their specific lens designs. Laboratories typically offer aspheric, segmented translating, post-refractive-surgery, and scleral multifocal designs. The consultants can recommend which lens to use, provide a diagnostic set if indicated, direct practitioners to pertinent resources on their laboratory’s web site, and assist with every step of the design, fitting, and troubleshooting process.

In addition, science and technology advances have provided us with tools not available several years ago, including topography maps, high-quality photographs, and video that is easily captured with digital devices.

TORIC SOFT MULTIFOCALS

When vertexed spectacle astigmatism is not equal to corneal astigmatism, GP lens designs may not be applicable. Toric soft multifocals are particularly attractive in these cases.

Fortunately, the availability of toric soft multifocal designs has exploded in recent years. Whereas a short time ago, designs of this nature were available only in custom or quarterly replacement modalities, several are now offered with a monthly replacement option.

When fitting toric soft multifocal lenses, make sure that the astigmatic error is properly corrected before employing any multifocal problem-solving strategies. To do otherwise will likely be an exercise in frustration, as residual astigmatism usually will adversely affect visual performance at both distance and near.

If a custom design is indicated, consider placing an initial order of three lenses per eye: one with toric power on the spectacle axis, and ones with toric power on either side of the spectacle axis. This approach improves fitting efficiency in the event that either lens rotates in a nasal or temporal direction.

The axis at which the off-axis lenses should be ordered depends on the astigmatic power in the lens. The higher the toric power, the closer the axis should be to the spectacle axis. This rationale has been explained in detail elsewhere (use Table 2 as a guide).¹⁷

CHOOSING A LENS

It’s important to choose the right type of multifocal contact lens to achieve success with each patient. How do you decide?

Happy with Habitual? When considering what presbyopia-correcting contact lens to recommend to a patient, answer these two questions: Is the patient currently wearing contact lenses? If so, is he or she happy with the lenses?

If a patient is happy overall but is having difficulty with near vision because of the onset of presbyopia, consider staying with that type of lens and adding multifocal correction to the prescription.

Patients who are frustrated with the performance of their habitual correction, for whatever reason, will be more open to other approaches. This may seem obvious, but it’s important to recognize because attitude plays an essential role in a patient’s ability to adapt to change.

Mulling over Modalities When soft contact lenses are the preferred option, which modality should we recommend? There is strong evidence that daily disposable lenses are the safest, most comfortable option with the best compliance rate when compared with other soft lens modalities.^18-20 These benefits make the daily disposable modality the first-choice option to recommend for most soft lens-wearing patients, including presbyopes.

SIMULTANEOUS VISION FITTING TIPS

Simultaneous optics, in which distant and near optics enter the pupil at the same time, are employed for many multifocal contact lens designs, including some corneal GP lenses and most, if not all, soft hybrid and scleral multifocal lenses. Here are some tips on fitting these widely available lenses.

Control the variables. The goal when fitting multifocal contact lenses is to find the visual balance that provides good vision at all distances. This balance is influenced by many factors, some that you can control, and some that you cannot. For example, add zone or distance zone sizes can be controlled in some GP and custom soft multifocal lenses but not in many frequent replacement soft lens designs. Most companies will recommend starting parameters. Be aware of what you can change for each design, and manipulate these parameters as needed.

If you’re unable to control lens parameters, control the environment. Your testing environment should mimic the environment in which your patients habitually function while wearing their lenses. This usually means with the room lights up and the patient viewing with both eyes open.

Test ocular dominance. Ocular dominance testing during contact lens fitting is an attempt to determine which of a patient’s eyes is given visual preference by his or her brain. Numerous studies have reported little correlation between sighting dominance (i.e., lining up an object with the hands or a tube) and success with monovision.^21,22 Similar results could be expected when employing different add powers between the right and left eyes. Other studies suggest that sensory dominance (i.e., determining which eye is more tolerant of blur) may be a better method, as it mimics what is done when prescribing asymmetric add powers.²³ The following cases illustrate the impact of eye dominance on multifocal lens success.

Case 1 A 47-year-old woman had happily worn monthly replacement multifocal lenses fit elsewhere, but she developed giant papillary conjunctivitis. A new provider refit her with daily disposable multifocal lenses; however, she reported blur at distance and near.

Additional examination revealed that the provider had assumed that the patient was right-eye-dominant and had prescribed a low add for the right eye and a high add for the left eye. Sensory dominance testing revealed that the patient was left-eye-dominant; after reversing the adds in the daily disposables, the patient was pleased with her vision. Further investigation showed that this was the approach that had been taken with her monthly multifocals.

Case 2 A 62-year-old man had worn GP multifocals in the past but had stopped wearing them because of ocular dryness, likely associated with an autoimmune disease. He missed the freedom that he had enjoyed with contact lens wear and expressed interest in daily disposable multifocal lenses for occasional wear. His spectacle prescription was OD –3.75 –0.25 x 170 and OS –4.75 –075 x 100, with +2.50D add.

Sensory dominance testing showed no strong preference. Sighting dominance testing indicated that the right eye was dominant. Therefore, a low-add lens was fit on the right eye, and a high-add lens was fit on the left eye.

Numerous attempts to manipulate distance and near powers were unsuccessful. Perhaps the uncorrected astigmatism in the left eye was the problem? Because toric multifocal lenses were not available in a daily disposable modality, the left eye was fit with a single-vision toric contact lens set for near vision. The patient, a physician, reported clear reading vision, but he had difficulty seeing his electronic health records at arm’s length. The amount of plus in the left lens was manipulated, but we were unable to achieve satisfactory vision at both intermediate and near with this approach.

Because the patient did not have a strong dominance preference with sensory dominance testing, we considered that reversing which eye was biased for near could solve the problem. The add in the right eye was increased from low to high, and the left eye was fit with a single-vision toric soft lens corrected for distance viewing. The patient was pleased with this result.

STEP UP TO ADD UP

It’s never been a better time to be prescribing presbyopia-correcting contact lenses. The wide array of multifocal tools available is impressive, including a comprehensive lens selection guide.²⁴ Step up and fit your next presbyope with multifocal contact lenses. It will add up to visual satisfaction for your patient and to professional satisfaction for you. CLS

REFERENCES

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