Perscribing for Astigmatism

Corrected Vision - Where do you draw the line?

RGP insights

RGPs Are Easy

August 2000

What has made rigid lenses so special has been their custom nature. The "art and science" associated with fitting RGP lenses is something that practitioners greatly cherish and consider a badge of honor. However, the harsh reality is that the industry has changed. The simplicity associated with the limited design parameters and shorter adaptation time of soft lenses ­ notably disposable lenses­ has changed the perception of contact lenses by both patient and practitioner.

The profession has also changed greatly in the last 25 years. Practitioners are diagnosing and treating eye disease as well as having an active role in the care of refractive surgery patients. From a time management standpoint, RGP lenses are often considered too complex and time-consuming. The following recommendations will make RGPs a more desirable option in these changing times.

1. A Material Solution. Do not allow the multitude of materials and different Dk values to represent a hurdle. I recommend a simple approach in which all daily wear myopes are typically fit into a low Dk (25-50) lens material. Although several materials have names such as ES, 30, 300, 500 and SGP3, no great differences exist among them. Ask your laboratory what its "bread and butter" material is. With hyperopes and flexible/extended wear patients, I use higher and hyper (>100) Dk lens materials. Have faith in your laboratory for the best material for your needs.

2. Present with Comfort. I always assume that a patient has previously been told that RGP lenses are uncomfortable. With that knowledge in mind, I present this option in a positive but realistic manner. Remember that the word "rigid" in itself can be threatening to a patient. Using a topical anesthetic at the fitting visit will also ease the patient into the adaptation experience.

3. Provide Vision. The greatest benefit of RGP lenses is vision. However, a very common method of fitting is selecting a -3.00D diagnostic lens for a patient who may have a refractive error much higher or lower than -3.00D. Combining initial lens awareness with less than optimum vision will not be a positive experience for the patient. Use a large diagnostic set or inventory with a wide range of powers. Or, take advantage of warranty programs provided by laboratories which encourage empirical fitting.

4. Simplify the Design. The recent introduction of ultrathin designs has been a blessing. Each lens is consistently thin which often results in improved lens centration and patient comfort. These standard designs use anywhere from only one to three diameters to simplify this specific parameter. One large manufacturer has a large diameter "comfort" design with a standard center thickness and periphery. Another laboratory has the option of providing its ultrathin aspheric design in a two-pack for the price of one pair. These programs minimize practitioner effort providing high quality lenses.

5. To Modify or Not? Many practitioners perceive modification as an obstacle for fitting RGP lenses. I believe that modifying RGPs is an important tool which provides immediate benefit to many patients. Instead of peripheral curve change and optical zone/diameter reduction, edge and surface polishing procedures are most important to learn and most commonly indicated. Modifications are relatively easy to perform and unlikely to result in any compromise in lens performance.

RGP lenses do not have to be complicated and, in fact, with many of the new designs and programs being introduced by laboratories, the fitting of this modality should continue to increase in both simplicity and patient satisfaction.

Dr. Bennett is an associate professor of optometry at the University of Missouri-St. Louis College of Optometry and executive director of the RGP Lens Institute.