Refitting Soft Multifocal Patients Into GPs
Patients seeking crisper vision from multifocals may benefit by switching to GP lenses.
By Phyllis Rakow, COMT, NCLE-AC, FCLSA
|Phyllis Rakow, COMT, NCLE-AC, FCLSA, director of contact lens services for The Princeton Eye Group, is a member of the NCLE Board of Directors and the GPLI Advisory Group. She has received travel funding from Blanchard Contact Lens.|
The development and widespread availability of soft multifocal lenses have reawakened an interest in presbyopic contact lens correction by current soft lens wearers and contact lens dropouts. With the United States presbyopic population at approximately 100 million, the pool of candidates is virtually unlimited.
What Are Patients Telling Us?
Our practice is located in an area with more than 10,000 homes in “active adult” communities. Many of our patients have worn soft lenses for much of their teen and adult lives and desire to continue to see and be seen without glasses. Most have transitioned reasonably well from single-vision spherical contact lenses to soft multifocals with low add powers, but satisfaction tends to decrease as time goes by and their near vision needs increase. When higher add powers are needed to perform routine near tasks, distance vision may be adversely affected. Do we want our patients to be 20/happy or 20/20?
When soft multifocal wearers with center-distance add powers complain that they are unable to attain satisfactory near vision, their typically small presbyopic pupils may be preventing them from reaching the maximum add. Conversely, if they are fit with center-near designs, their small pupils may preclude satisfactory distance vision. With higher add powers, some soft multifocal wearers are unable to resolve simultaneous images and complain of ghosting and the “3-D” effect, especially when reading. Another complaint we hear frequently from presbyopic soft lens wearers is that their vision and comfort decrease as the day progresses.
Patients who have 0.75D or more of refractive astigmatism generally complain of decreased vision at both distance and near with soft multifocals. Although there are now two planned replacement and several conventional soft toric multifocal lens designs, fitting fees and material costs are high, and rates of success relatively low, in my opinion. In many practices, presbyopic astigmats who currently wear—or are being fit with—soft lenses ultimately wear toric single-vision lenses and either reading glasses over their distance contact lenses or monovision, with its inherent compromises. Amblyopic astigmats have even greater limitations with soft lenses as monovision is not a viable option for them.
Consider GP Multifocals
Some fitters hesitate to recommend GP lenses to mature adults because they fear that patients will not be able to adapt to a rigid material at this point in life. By leaving these patients in soft lenses, both visual acuity and corneal health are compromised. Placing a diagnostic GP lens on astigmatic patients' eyes will often produce a “wow” factor when patients realize how sharp and stable their vision is. Patients who have keratometry values greater than 45.00D in both principal meridians are often unable to achieve rotational stability with soft toric lenses. Many of these patients, if they have worn soft toric lenses (especially low-water-content toric designs) in the past, will also show signs of corneal hypoxia, including neovascularization under the base of the prism, and even inferior corneal ectasias that simulate early keratoconus.
As astigmatic patients enter their presbyopic years, they will find soft lens options even more limited. A multitude of excellent GP multifocal lenses are available in anterior- and posterior-surface designs. Some of the posterior-surface designs allow you to incorporate an additional concentric zone of add power on the anterior surface of the lenses for mature presbyopes. As most patients today spend time at a computer, we prefer using a multifocal GP to an alternating vision bifocal design whenever possible.
In our practice, if presbyopic patients express frustration with their current soft lenses or if we can demonstrate the limitations of their soft multifocals, the time is right to present the advantages of GP multifocals. While it is not uncommon for these patients to have been told that they will have to live with their frustrations because that is the best that can be currently achieved with soft multifocals, we carry the conversation to the next level.
Have the Conversation
We ask the following screening questions to soft multifocal patients.
1. Did you ever wear rigid lenses in the past? If so, why did you switch to soft lenses?
Some patients will tell you that they were doing well with rigid lenses, but switched “because it was the thing to do—everyone was getting soft lenses.” These patients are easy to convince that GP multifocals are worth a try. They have expressed their disappointment with soft multifocals and are highly motivated. They are willing to trade immediate comfort for crisp vision, for they have adapted successfully to rigid lenses in the past and understand that it takes a little time to achieve optimum comfort. Other patients who had been successful GP lens wearers have told us that they were refit with soft lenses because they were unable to find a doctor who still fit GPs. They are delighted to learn that we not only fit GP lenses, but that there are GP multifocals.
Rigid lens dropouts coming from active adult communities range in age from 55 to 80, so many were fit with polymethyl methacrylate (PMMA) or early, very low-oxygen-permeable (low-Dk) GP lenses. For some individuals in this group, spectacle blur and corneal warpage were major concerns. We discuss the fact that today we now have hyperpermeable GP materials and lens designs that should not cause any significant spectacle blur. The very steep posterior surface multifocals that so often caused spectacle blur in the past have been relegated to the replacement market for the most part, and the majority of new GP multifocals are anterior-surface or bi-aspheric designs that are fit conventionally, similar to the fit of a single vision lens.
Soft lens wearers who have never tried GP lenses may be apprehensive about initial comfort. With them, we discuss the advances in material technology in layman's terms. “The lens material is made up of an acrylic plastic, like Lucite or Plexiglas, to give it its strength, silicone to make it permeable to oxygen, and a third component that is similar to Teflon. This enables the lens to glide more smoothly on your eye and allows protein deposits to be blinked easily off the lens surface.” Occasionally, the question about whether the “Teflon” will peel off, like it did on the patient's frying pan, comes up. We explain that the three components are mixed in the liquid state and heat-cured in molds, and that nothing will separate and peel. We also discuss the advantages of plasma treatment with our patients and include it automatically on GP multifocal orders.
2. How do you use your eyes? Are you still working? Do you drive at night? Do you need good near or distance vision for crafts, hobbies, or recreational activities? Do you read a lot?
Many GP multifocal options are available, and our rate of success depends on finding the lens design that will best meet the needs of each patient. Most current soft multifocals have a fixed center optical zone that cannot be adjusted to accommodate different pupillary diameters. The optical zone of most GP multifocals can be customized for different pupil sizes. In addition, GPs provide better all-range vision because they combine translation with simultaneous vision—enhancing near vision as patients look down and the lenses translate upward and decreasing pupil dependency for optimum vision.
Most GP laboratories have developed proprietary multifocal designs that meet the needs of a wide range of candidates. Most of my multifocal patients have been fit with lenses from Art Optical and Blanchard Contact Lens, laboratories that we have used for many years for our general GP needs, but the basic principles presented here will also apply to the selection and fitting of other anterior-surface GP multifocals. As multifocal diagnostic fitting sets are not readily available and several would be required to fit a wide range of myopes and hyperopes, it is important to establish a good relationship with the laboratory manager and consultation staff of your preferred vendors. They will provide invaluable assistance and help you rapidly manage the learning curve. To order empirically, you will need patients' refraction, reading add power, vertex distance (if applicable), keratometry readings, pupillary diameter in ambient and mesopic lighting conditions, and horizontal visible iris diameter (HVID). Once you are familiar with the available lens designs and fitting criteria, nomograms are usually available to assist in choosing the initial parameters. All GP laboratories offer generous guaranteed fit programs for their multifocal contact lenses.
We tell our patients that the adage, “It takes a lens to fit a lens,” is more true when fitting multifocals compared with most other lenses, and we explain that, “because fitting sets are not usually available, the first set of lenses that we order will become our diagnostic lenses. They may be perfect; however, if not, they will give us the information we need to adjust the fit and improve your vision and/or comfort.” We explain the adaptation period and use the analogy of how comfort gradually increases as we break in a new pair of shoes. We pull the patients' lids apart to demonstrate that most of the initial sensation comes not from the cornea, but from interaction of the lens edge with the lids. We ask our laboratories to taper edges well and roll them slightly inward to optimize comfort.
For patients to whom distance vision is a priority, such as golfers, hunters, tennis players, patients who have larger-than-average pupils, and those who drive frequently at night, an anterior-surface multifocal with a large central distance optical zone, like Art Optical's MagniClear Plus (Figure 1) is a good choice. This lens has a standard 7.0mm, low-eccentricity distance zone; a 0.5mm transitional aspheric intermediate zone; and a 1.0mm spherical near zone with add powers available up to +4.50D. Good translation is necessary to access the full add power; otherwise, patients will be limited to the power of the aspheric intermediate zone for reading. We have found that the large distance zone makes the MagniClear Plus a good choice for emerging presbyopes, patients who do not have critical near vision demands, and patients who have experienced halos and starbursts when driving at night.
Figure 1. MagniClear Plus lens.
Moderate and mature presbyopes, especially those with greater near demands, may achieve more success with multifocals that allow greater flexibility in design, such as Art Optical's Renovation (Figure 2) and Blanchard's Reclaim (Figure 3). Both modalities allow you to adjust the diameter of the distance optical zone to account for variations in pupil size as well as distance, intermediate, and near needs. The aberration control of these lenses helps to improve contrast and provide clear visual acuity throughout the entire range of focus. Both lenses have an aspheric posterior surface with a low eccentricity value and, because they fit like spherical GPs, corneal integrity is maintained. It is rare to hear complaints of spectacle blur from patients wearing anterior-surface GP multifocals.
Figure 2. Renovation lens.
Figure 3. Reclaim lens.
3. Do you have problems with dryness when you wear your soft lenses?
Dryness is endemic in the presbyopic population and is not limited to menopausal and postmenopausal women. Men and women in the presbyopic age group may have diabetes, thyroid disease, arthritis, other collagen diseases, or may be on medications that cause dry eyes. They have expressed their frustration with soft lens vision that decreases as the day progresses and they want stable acuity throughout the day. Materials such as Hydro 2 (Innovision Inc.) and Onsi 56 (Lagado Corporation) are inherently wettable and will provide vision that remains constant all day long; plasma treatment will also help.
Tips For Fitting and Problem-Solving
Some GP laboratories allow you to keep the original lenses when changes are made, so in time you may be able to build a small fitting set. It's important, however, when choosing the base curve, to never use a minus lens on a hyperope or a plus lens on a myope. The mass, weight, and forward center of gravity of a plus lens will usually cause it to ride much lower compared to the same base curve in a minus lens and will mislead you regarding the choice of a base curve. Likewise, power differentials of more than 3.00D or 4.00D will alter the lens profile and may also require compensations for vertex distance.
Previous soft lens wearers may experience excessive tearing when GP lenses are applied for the first time. Instillation of a topical anesthetic may help and enable the lens to settle in more quickly. Our fitting criteria include good centration, lid attachment, and apical alignment.
Refine distance vision using a trial frame or loose lenses because the phoropter will cause alterations in pupil size that might affect vision. If distance vision is not acceptable, the lens may not be well centered or the anterior optical zone may be too small, resulting in the patient looking through the intermediate or near zones. The base curve, optical zone diameter, and overall diameter should be reevaluated. Residual astigmatism may also cause reduced distance acuity.
If near vision is a problem, evaluate the lenses for translation. Translation will be easiest to attain in patients whose lower lids are at or slightly above the inferior limbus. If the lids are loose and flaccid or significantly below the inferior limbus, translation may not be possible. Unsatisfactory near vision may also be due to residual astigmatism, insufficient add power, or an anterior optical zone that is too large. If the patient has already been given the maximum add, +0.50D to +0.75D of additional add power may be possible if the lens is manufactured in a high-refractive-index material such as Contamac HR with a refractive index of 1.53 or Paragon HDS HI (Paragon Vision Sciences) with a refractive index of 1.54.
Patients who have larger-than-normal pupils or anterior optical zones that are too small may experience flare. These patients may need a lens with a large distance zone, such as the MagniClear Plus, or a lens in which the distance optical zone can be specified by the fitter. If the flare is caused by decentration or inferior pooling, adjust the base curve radius. Complaints of ghosting are generally due to decentered lenses, residual astigmatism, or the inability to resolve simultaneous images. Resolution of simultaneous images is less of a problem with GP multifocals than with soft multifocals, and often resolves with time.
We dispense well-fitting lenses only if distance vision exceeds the minimum requirement for a driver's license in our state. Near power and overall diameter can be adjusted, if necessary, at a follow-up visit, but our patients must be safe on the road. We advise our patients who are still in the active workforce to begin wearing their lenses on a weekend or while they are on vacation when their visual demands are not as critical. We make sure that they are able to apply, remove, recenter, and clean their lenses without difficulty before they leave the office as the techniques and care products are new to them, and we make sure that we emphasize the many advantages of GP contact lenses. CLS