By PAT KEECH, O.D.,
KEITH AMES, O.D.
Shoreline, Washington

Presbyopes are best served when you offer optometric care with a full scope of contact lens options. If you have tried only soft lenses, then you"ve only just begun. Effective RGP multifocal fitting builds both your practice and your professional self-esteem. By thinking outside the box, you will be rewarded not only with referrals and insurance reimbursement, but also by many grateful presbyopic patients. While current RGP wearers are obvious candidates, soft lens wearers and non-lens wearers also are viable candidates. The only patients not suitable to try this type of correction are those with no significant distance refractive error or those unwilling or unable to wear contact lenses full-time.

With an appropriate trial-lens selection and the ability to listen to the patient"s requirements, you can achieve success. You can control RGP multifocal visual performance either by selecting an appropriate design or by varying the lens parameters to adjust the mechanical fitting relationship of the lens. Here"s how to get started.

ASPHERIC DESIGNS
You will need at least two or three RGP designs to mix and match, including trials in at least one aspheric design (simultaneous vision) and one translating design (prism ballasted). Aspheric designs work better for computer users unless they work on laptops. Since computers are now ubiquitous, many people need good intermediate vision, so be sure to ask about your patient"s requirements.

FIG.1: Preferred fitting appearance for patient wearing a prism-ballasted design.

FIG.2: Lens immediately after blinking rides high at first.

Test the distance and near acuity and ranges binocularly. Some patients prefer the closer working distance, while others want to maintain good intermediate vision and wear readers occasionally for pr olonged near work at a closer working distance. For most computer users, simultaneous-vision aspheric designs work better for intermediate vision. Some patients may want auxiliary glasses that equalize the eyes for distance when driving. Tailor the permutations and combinations for each individual patient.

Translating designs are preferable for patients with more traditional reading positions and those who do prolonged near work. Lid position and pupil size are more crucial for the translating designs. I tend not to truncate these designs, since it limits the effectiveness of the prism ballast. If the pupils are too large (greater than 4mm) or the lower lid too lax, you may need to go to the high-riding aspheric designs. As the aspheric options have improved, I find myself using them more frequently. Patients achieve good comfort with remarkable speed.

As with any new fit, you can experiment with two different brands or designs, or use different parameters on the two eyes to compare fit and function. This minimizes chair time, and you can glean a great deal of information with minimal effort. Many patients end up wearing two different brands of lenses, enjoying the optical advantages of both. Unequal adds extend the near range for the patient.

TRANSLATING DESIGNS
Alternating-vision designs usually provide the least compromised vision because their on-eye movement allows for distance and near optics at different times. Alternating RGP multifocal lenses work by means of upper-lid attachment and lower-lid interaction. Lid-attached designs require the upper lid to cover at least a portion of the upper limbus so that larger and slightly flatter lenses position superiorly for maximum effectiveness. Lower-lid-interaction designs are prism-ballasted and require a lower lid at or near the lower limbus to support the slightly steeper-fit, inferiorly positioned lenses.

Consider these guidelines to maximize your practice efficiency and minimize your and your patient"s time commitment:

 Don"t fool Mother Nature. Focus on the patient"s lid anatomy rather than vision requirements, and try to fit the lens Mother Nature intended. If the patient has a relatively narrow aperture with a good upper-lid position, attempt a lid-attached fit. If the aperture is wider with good lower-lid support, try a prism-ballasted fit, since the upper lid will be less involved.

Patience is a virtue. Consider the first lens you dispense a trial lens. Avoid making changes too early. Allow the patient to at least partially adapt before considering any parameter changes. These lenses often can be fit empirically with acceptable reorder rates.

CASE STUDY
Consider a case example that demonstrates how to achieve success with no previous RGP experience and minimal chair time.

Spotting Candidates

Many bifocal candidates aren"t even aware that contact lenses are an option for them. The most overlooked patients are those new to glasses. Many don"t like the limitation of their peripheral field or the limited reading area in their bifocal or progressive spectacles. RGP multifocals work especially well for the new presbyope who now needs a distance prescription. Low hyperopes are another group for whom RGP multifocals are an attractive option. When a patient has outgrown the available monovision or single-vision options, it is time to embark on a bifocal fitting. You can spot motivated patients by their interest in seeing without spectacles or readers. Explain that fitting requires both a commitment to the process and acceptance of some visual compromise. Explain that you will find the best available compromise for their visual function. If they are not willing to make that commitment or accept some visual compromise, inform them that bifocals are not for them. A signed contact lens fee agreement, spelling out the costs and expectations, avoids surprises.

A 50-year-old female who wore soft monovision contact lenses successfully for six years complained that reading and close work were becoming increasingly difficult. She was ready to give up contact lenses if this was the best we could do.

Her parameters were O.D.: ­1.50 ­.50 x 90, 45.00/45.00 @ 90; O.S.: ­3.00 ­.25 x 90, 45.00/45.25 @ 90. The lid configuration was characterized by moderately wide apertures with acceptable upper- and lower-lid positions O.U.

A prism-ballasted design was the best choice, since her work entailed primarily written-document review rather than computer use. The initial parameters ordered were O.D.: 7.50 mm base curve, 9.6 mm diameter, ­1.50/+2.00 add, medium prism, seg 1 mm below center; O.S.: 7.50 mm base curve, 9.6 mm diameter, ­3.00/+2.00 add, medium prism, seg 1 mm below center. The material was the XCEL Solutions Bifocal, HDS, Paragon.

The lenses showed acceptable positioning, fluorescein patterns, and movement at dispensing, and the initial visual acuity was 20/20 at distance and near. Figure 1 conveys the fitting appearance preferred with this type of lens. After one week of wear, the patient reported overall satisfaction but a bothersome fluctuation of vision at distance, especially after blinking. Figure 2 shows the left lens after blinking, riding high and taking a few seconds for the lens to drop to the pre-blink position.

We ordered a second lens for the left eye with identical parameters except an increase in prism ballasting to maximum prism; this lens comes in minimum, medium, and maximum prism. The new lens showed much better dynamics on the eye and quickly dropped to the pre-blink position after the blink. Her distance-vision fluctuation decreased without sacrificing near vision. The higher-minus lens--which was interacting with the upper lid more, riding higher and dropping more slowly after the blink--benefitted from increased weight.

This example reinforces several points about fitting this type of lens. First and foremost is exceptional visual acuity. The fitting process does not have to be cumbersome, provided you pay close attention to the aperture/lid configuration and solve problems logically to improve the patient"s visual performance.

Offering full-scope presbyopic contact lens services is a great source of referrals from your colleagues and from satisfied patients. Don"t ignore this interesting and rewarding area of practice. Next time you"re ready to tell that soft-lens-wearing presbyope there"s nothing else you can do, give RGPs a try.

Drs. Keech and Ames specialize in fitting contact lenses. They prescribe both aspheric and translating RGP bifocal designs.