Multifocals 101

BY MARY JO STIEGEMEIER
May 1999

Build your practice and boost patient satisfaction by honing your expertise with multifocal
contact lenses.

As the population ages, it is estimated that by the year 2000, there will be 100 million presbyopes in the United States. However, only 1 million of these people currently wear contact lenses, with 700,000 wearing monovision and 300,000 wearing multifocal lenses. This represents the largest untapped contact lens market today.

Although presbyopic contact lens fitting can be difficult and time-consuming, today's technology offers many more options and modalities, improving success rates and decreasing chair time. By successfully fitting these patients in lenses, you gain growth potential and loyalty from these patients.

Broaching the Topic

Although the topic of multifocal lenses is likely to arise for patients who already wear lenses, it's important to remember to mention contact lens options to the nonwearer. Patients must understand all of their options. Many do not know whether or not they are good candidates for contact lenses and are reluctant to ask questions if you don't introduce the topic.

Screening Patients Properly

To achieve a high success rate with multifocals, it's best to screen your patients adequately. Before the fitting, talk with your patients about their expectations for lens wear and their visual needs for work and hobbies. I also discuss fitting and lens costs and explain fees and office refund policies in case their fitting is unsuccessful. This helps determine their level of commitment. Fit only patients who have better than a 50 percent chance of success.

Once you commit to fitting the presbyopic patient, convey your enthusiasm. This attitude also should be reinforced through your staff -- from the receptionist to the contact lens technician.

Evaluating the patient's current lens helps me select the bifocal design, material and lens size and determine the lens-to-cornea relationship. I prefer to overrefract their lenses to ascertain residual astigmatism and add power. The patient's pupil size in ambient lighting, upper and lower lid positioning, and tonicity influences the type of bifocal lens chosen.

Special Considerations and Challenges

Several physiologic changes in the eye and adnexa associated with advancing age are relevant to multifocal lens wear. The two major changes I consider are changes in the lids and tear production.

With age, the orbicularis oculi lose elasticity, causing a gradual loss of tonus and changes in the interpalpebral aperture. This affects multifocal contact lens wear because the lower lid may not be able to support the lens or the lower lid tone may not be adequate to control the segment height. General lid tonus is also important in lens removal.

Secondly, tear flow gradually decreases as a person ages. These patients also may take systemic medications or have systemic conditions affecting tear film integrity. With these considerations, several options are available to the presbyopic patient.

In addition, corneal shape and refractive and lenticular astigmatism must be evaluated. These values are useful in choosing between a rigid gas permeable (RGP) and soft lens design.

Fitting Techniques for Presbyopia

I view presbyopic lens fitting as a continuum -- from the early presbyope who has never worn lenses to the absolute presbyope. I categorize presbyopia cases into early, moderate or absolute stages, using this as a guide to fitting lenses. Several fitting approaches work well for different levels of presbyopia.

Refractive Compensation -- I use refractive compensation for patients with early presbyopia -- those new to contact lenses, as well as established wearers. This term refers to simple binocular overcorrection of hyperopia or undercorrection of myopic distance refractive error to improve near acuity. This works exquisitely in patients with low hyperopia and early presbyopia. Many of these patients function uncorrected most of their day. Applying their full hyperopic correction or slightly overcorrecting their hyperopia with single-vision contact lenses dramatically improves their near and intermediate vision and slightly improves their distance visual acuity.

Monovision and Modified Monovision Contact Lenses -- These work well in patients with early or moderate levels of presbyopia. The dominant eye (usually) is for distance, while the nondominant eye (usually) is corrected for near vision. Although it seems contrary to theories of binocular vision, patients maintain some stereopsis because peripheral vision remains largely undisturbed, but reaction times may increase significantly. Again, patients with low uncorrected hyperopia do very well with this technique because addition of plus does not decrease distance acuity and can only help intermediate and near vision. When using this technique, do not overlook the possibility of distance overcorrection for night driving.

Bifocal Contact Lenses -- Patients advancing from moderate to absolute presbyopia sometimes complain about inequality or imbalance in their vision at distance or near. Fortunately, several bifocal designs and modalities address visual acuity and binocularity issues.

As you know, two basic types of bifocal lenses are used: alternating, in which distance optics are over the pupil in primary gaze, while near optics are over the pupil in downgaze, and simultaneous designs, in which distance and near optics are within the pupillary area at all times. Patients learn to "cortically adapt," ignoring the near image that is out of focus while viewing a distant point, and ignoring the distant image that is out of focus while reading.

I initially fit emerging presbyopic patients with simultaneous vision lenses. These lenses work very well in computer users, who rely on intermediate vision for a good portion of their workday. Simultaneous vision lenses are available in disposable, daily and extended-wear modalities. I like them because I can demonstrate vision and comfort immediately with trial fitting lenses and adjust prescriptions immediately if necessary. The health benefits and convenience offered by disposable lenses are also well known. Patients often leave the office that day with bifocal trial lenses while they are still motivated and enthusiastic. Simultaneous vision lenses used to lack bifocal power, but newer modalities boast a true +2.50 add power.

I offer RGP simultaneous vision lenses, aspheric designs, for patients wearing RGP designs or soft toric lenses or if the lower lid is below the limbus.

I opt for an alternating design for the mature presbyope or when a patient wearing a simultaneous vision design needs increased add for near vision. The lower lid must be firm enough and in the correct position to support the lens and afford translation. This lens style also works best if the pupil diameter is moderate to small.

Modified Bifocal Contact Lenses -- This technique is correcting presbyopia with either a single-vision contact lens in one eye and a bifocal in the other or two bifocal contact lenses with unequal adds. With this technique you may increase your success rate by tweaking the power to fit a particular patient's needs. For example, a golfer who wants to maintain binocularity and see well in the distance but also wants to read his score card and view at an intermediate range (for putting) may use a full-distance bifocal in the dominant eye with an intermediate add and center distance bifocal in the nondominant eye with full near add.

Hybrid Bifocal Lenses -- Finally, a hybrid lens system can maintain binocularity and ease the imbalance of monovision even in advanced presbyopia. These complementary systems provide the patient with good distance, intermediate and near vision. The dominant eye is fit with a distance center intermediate surround simultaneous vision lens, while the nondominant eye is fit with a near center intermediate surround simultaneous vision lens.

Successfully Fitting Monovision Lenses

To fit presbyopic patients successfully, choose a few lenses in each design as your "workhorse" lenses. No single design is perfect for all patients. Know those designs well and when to use them. Use trial sets if possible. With about six types of lenses, you should have an 80 percent success rate for fitting within two to three visits. Charge appropriately for the lens type, your expertise and your chair time.

Because of the newest technology, I actively promote bifocals and use them as my lens of first choice. If they fail, I rely on monovision as a second choice. Although fitting bifocal lenses is not without challenges, when you are successful your patients will be loyal and your referrals will increase.

Dr. Stiegemeier is in private practice in Chesterland, Ohio. She lectures throughout the country on the subject of contact lenses and performs clinical research.