Article Date: 10/1/2008

A Different Method for Diagnostic GP Lens Fitting
contact lens case reports

A Different Method for Diagnostic GP Lens Fitting


Gas permeable fitting with diagnostic lenses is the cornerstone of every specialty contact lens practice. However, diagnostic fitting can be somewhat disconcerting for the following reasons:

• The image portrayed to the patient at the time of the diagnostic fitting, especially if an older diagnostic set is used (Figure 1).

• Questionable cleanliness and safety of the diagnostic lenses.

• Previous fitters may have returned lenses to incorrect storage cases.

• The diagnostic lenses may not be the laboratory's most up-to-date design or may have been manufactured on equipment that has been replaced by modern computer-controlled lathing systems.

• Rarely are the diagnostic lenses the appropriate power for the patient's ocular requirements.

• Wasted chair time, required to clean the lens and verify the parameters prior to application.

Figure 1. A traditional diagnostic lens set. Imagine the thoughts going through patients' minds as we select diagnostic lenses.

A New System

We are currently evaluating a new GP delivery system from Paragon Vision Sciences called SureFit. With SureFit, the practitioner provides the laboratory consultant with a patient's Ks and prescription, and together they determine the most appropriate contact lens design for the patient. The consultant then selects two to four different base curve and power combinations for each eye. The lenses are shipped in sealed, wet-storage blister packs labeled by letters starting with A. (Figure 2).

Figure 2. The SureFit diagnostic/dispensing system.

The blister pack includes directions to use the "A" lens first. This is the lens the laboratory has determined is most likely to be successful. If this lens fails to provide the appropriate lens-to-cornea fitting relationship or vision, evaluate lens "B," and so on. This systematic analysis of new, clean and accurate diagnostic lenses may help in determining optimum lens parameters.

Put to the Test

Our patient was a 46-year-old female interested in multifocal GP lenses. Her spectacle Rx was OD –1.50 –1.75 ×010 and OS –2.00 –1.50 ×170 with a +1.50D add and VAs of 20/20 at both distance and near. We forwarded the patient's Ks and Rx to the laboratory consultant and received three lenses for each eye manufactured in the laboratory's most up-to-date multifocal design.

We noted that the "A" lenses were slightly flat; ultimately the "B" set provided optimum lens centration and movement. The resulting binocular acuities were 20/20 at distance and at near.

Once you successfully fit a patient, you can discard the remaining diagnostic lenses. For us "older" practitioners, this requires a complete rethinking of how we dispense GP lenses.

While the SureFit System may not be appropriate for all practices, for some it may represent a fast and accurate way to diagnostically fit more complex lens designs. CLS

Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Paragon Vision Sciences. Mark André is an associate professor of optometry at Pacific University. He is also a consultant for CooperVision.

Contact Lens Spectrum, Issue: October 2008