The Secrets to Success With RGP Multifocals

Take it from the experts. Knowing just a few general principles can help you get and keep more presbyopes in RGPs.

BY CAROL A. SCHWARTZ, OD, MBA, & EDWARD S. BENNETT, OD, MSEd
JUNE 1998

Why do some practitioners enjoy fantastic success fitting RGP multifocals while others insist that they just don't work? Obviously there's a secret to multifocal fitting -- something so elusive that even those who have it can rarely articulate it. We surveyed a subgroup of the Rigid Gas Permeable Lens Institute's Advisory Committee to try to find an answer.

The Advisory Committee consists of over 50 U.S. contact lens practitioners who have been recognized by their laboratory or by industry leaders as having exceptional skills in rigid lens fitting. Eighteen of these who have special interest and/or great success with rigid multifocals participated in the bifocal success project. One-third of this group fit over 40 percent of their presbyopic contact lens patients in RGP multifocals, fitting over six multifocal patients each month. When asked what factors they take into consideration before presenting options to patients, the respondents offered a variety of pearls.

Overcoming Obstacles

Start by presenting all of the patient's options, stressing the advantages that RGP multifocals have to offer, including crisp vision, easy care and handling and longer lens life than soft contact lenses. To find the best match for each patient's needs, first explain the different design types and how they work. Explain that despite the complexity of these designs, they will work, but not as well as eyeglasses. When patients know this up front, they are generally happy. One respondent noted that he always compares the lenses to a crescent wrench or sewing machine, telling patients that if they learn to use them properly, the lenses will serve them well. The perfect candidate already wears RGPs successfully, is highly motivated and does not want to use eyeglasses. Any patient fitting this profile, such as the 40-something current RGP wearer complaining of near blur at a follow-up visit, is a very likely candidate for RGP multifocal success.

Fitting existing RGP contact lens wearers can be a mixed blessing. Having already passed the adaptation hurdle, these wearers take to prism ballasted lenses easily, but they may have unrealistic expectations of a difficult and time-consuming fit. One practitioner noted that he is more aggressive with current wearers in his case presentation, assuring them of an 80 to 90 percent chance of success.

Building Confidence

The only way to become confident is to fit lenses successfully. Five of the 18 practitioners we surveyed felt that only three or four fits were necessary to become comfortable fitting RGP bifocals. Eight practitioners felt that the basic tool kit should include three fitting sets -- one each of aspheric, concentric and segmented designs. All respondents recommend knowing which designs work best with visual needs and lid anatomy.

Remember too, that the confidence the practitioner has in the type of correction is key to motivating and instilling confidence in the patient. If you're hesitant or skeptical about the modality, patients will pick up on it no matter how good of an actor you think you are. "If you're wearing the lenses successfully, you'll demonstrate to potential wearers that they work," one respondent said. Others noted that knowing the basics of RGP fitting helps, as does having a large RGP practice. The manner in which you charge may also make a difference. Many of these practitioners have set up a nothing-to-lose, everything-to-gain fee schedule in which the patient pays only a fitting and exam fee until a satisfactory pair of lenses is found. Warrantied lens prices make this a viable option.

TABLE 1: Physical factors that influence fitting LID POSITION This factor is critical to the success of translating designs. If the lower lid is below the limbus, the patient may not access the near correction on downgaze. Consider fitting aspheric designs. A high upper lid position is best for aspheric designs that require good centration. If the upper lid is too low, consider fitting an aspheric designed for a lid-attached fit. LID TORICITY A too-tight lid can hinder the centration of aspheric or concentric designs; a too-loose lid may not support translating lenses. Evaluate diagnostic lenses carefully for lid capture. PUPIL SIZE Patients with very large pupils may experience ghost images with aspheric bifocals, and large pupils may complicate the fitting of some translating lenses. Very tiny pupils may prevent efficient near correction in aspheric and some concentric designs. A rule of thumb one expert offered is to fit pupils greater than 5mm with translating lenses and to fit those smaller than 5mm with aspheric lenses. CORNEAL TOPOGRAPHY Not all of these successful fitters use a corneal topographer. Those who do use it concentrate on acquiring information about the location of the corneal apex. If the apex is centered, a concentric or aspheric design is feasible; if it is inferior, a translating lens may be most successful; and if it is superior, a lid-attached lens works best. TEAR FILM A good precorneal tear film is a must when fitting RGP multifocals.

Who Not To Fit

Part of the reason these practitioners are successful is because they are able to rule out poor candidates before they begin diagnostic procedures. Exclusionary factors can be: psychological -- negative attitude, excessive expectations, impatience and lack of motivation; situational -- occupations that demand perfect near vision (i.e. accountants), current soft lens wear, no previous contact lens experience, work in dusty environments and the need for precise night vision (i.e. long distance truckers), or physical -- patients with low myopia or hyperopia, emmetropic presbyopia, poor tear film, large amounts of internal astigmatism, extremely high refractive error, keratoconus and absolute presbyopia (add 2.50D). Table 1 lists the physical factors that affect the fit of an RGP multifocal contact lens.

Obviously, the amount of near work patients do and the amount of time they spend working at a computer are important considerations. Translating designs generally provide a better result for those with intense near demands. For those with an intermediate demand, an aspheric design will provide variable powers. An aspheric bifocal is the best design for early presbyopes who use computers. Segmented designs, followed by aspherics, are preferred for nearly absolute presbyopes. Most experts would fit a segmented lens when clear distance vision is a critical demand.

Modified Monovision

Modified monovision is popular among this group of practitioners, particularly one conventionally fitted bifocal on the dominant eye and one fitted for intermediate and near vision on the nondominant eye. They may also fit a single vision contact lens for distance on the dominant eye and a multifocal lens for intermediate and near use on the nondominant eye. Consider these and similar variations when the lower lid position makes fitting a translating multifocal impossible, when the patient requires intermediate correction, when a successful aspheric design patient needs a little stronger add than is available in their design, or when one design fitted on both eyes does not yield satisfactory vision.

Dr. Schwartz is a contact lens consultant in vista, ca, and is editor of specialty contact lenses: the fitter's guide.

 

Dr. bennett is a professor at the university of missouri and is executive director of the rgp lens institute.

 

More Multifocal Fitting Pearls For Aspheric Multifocals: Centration is critical (unless fitting a lens that must position with the upper lid) Fit for minimum acceptable movement The lower edge of the lens should be 0.5mm to 1.0mm below the pupillary margin Decreasing diameter reduces edge lift and therefore decreases movement Pupil size is more critical with front-surface designs Some designs require over-plussing For Segmented Translating Multifocals: All require different segment positions-- use the manufacturer's guide for each lens If the lens rotates nasally, flatten the base curve; if rotation is temporal, steepen the fit Use a reticule in the biomicroscope to make measurements Lens should center laterally and move quickly Use enough prism to get the lens to drop quickly after blink View seg position in primary and down gaze with an ophthalmoscope at arm's length Position the seg line just into the pupil in primary gaze; too low is better than too high Avoid too large a diameter to enhance translation Measure seg height with a cobalt filter in dark conditions Always overestimate seg height by 0.2mm to 0.4mm; modify in-office fit as needed Use more prism for high minus corrections For Concentric Translating Multifocals: Centration is critical Avoid fitting patients who have small pupils Fit for rapid recentration after the blink Glare usually resolves within three weeks Use a front toric for residual astigmatism Reduce flare by using aspheric junction Recommended for high near and distance demand