Corneal Topography: The Harbinger of RGP Quality

BY EDWARD S. BENNETT, O.D., M.S. ED.
DEC. 1996

RGP lens quality continues to improve and new technology is largely responsible. While Computer Numeric Controlled (CNC) lathing and advances in the polishing process have led to better accuracy, reproducibility and comfort, today's RGPs must also give credit to corneal topography.

In the following investigative report, I asked representatives from several Contact Lens Manufacturers Association (CLMA) member laboratories to identify the impact of corneal topography on RGP fitting now and in the future.

RELAX, YOU'RE NOT OBSOLETE

It's evident that the role of corneal topography will increase with future RGP lens design, fitting, ordering and fabrication. "There's little doubt that in the near future, contact lenses will be prescribed, ordered, downloaded onto a lathe, manufactured and mailed to the doctor automatically," according to Philip Buscemi, O.D., a private practitioner and consultant to Tomey Technology, Inc.

Corneal topography will not, however, replace diagnostic fitting entirely. "No matter how great the technology is, the doctor examining the patient with the contact lens on the eye can never be superseded by automation," Dr. Buscemi said. "The nuances of contact lens fitting are still an art and will stay that way for some time to come."

One reason corneal topography poses little threat to diagnostic fitting is because it still does not take into consideration the power of the lens (lens shape and profile), lid tension, palpebral aperture, tears, blink rate and other details, according to Carl Moore, president of Con-Cise Contact Lens Co.

COMPETITION IS HEALTHY

Moore sees topography's greatest contribution as "the higher standards of success it will generate when we realize what a proper fit versus an improper fit will do to the cornea." He predicted that corneal mapping will "press the industry and professions to greater achievement in lens designs and materials."

The CLMA's Seal of Excellence program also encourages quality. Member laboratories that pass the testing program may exhibit the seal on their letterhead and in advertising. According to Moore, "This has challenged the industry to move to a higher plane and may also be a reason why laboratories have improved in manufacturing excellence."

SHARPEN YOUR FITTING SKILL

Topography helps the inexperienced and the experienced fitter alike. It enhances the confidence of the inexperienced fitter, who will "learn much sooner that the lens actually fits the mid-periphery of the cornea rather than the center, and will become proficient much quicker," said Frank Mastroianna, vice president of Precision Vision, Ltd.

For practitioners who are experienced with RGP fitting, Mastroianna said that specialized fitting of abnormal corneas will be topography's most valuable role. This includes the postsurgical cornea.

"With an increase in the number of refractive surgery patients who need contact lens correction, corneal topography is a necessity," said Michael Elton, director of marketing for Omega Group. Comanagement of postsurgical patients can be quite profitable for practitioners, Elton noted, and initial topography screenings by optometrists could foster symbiotic relationships between the surgery centers and the O.D.s.

BONDING WITH YOUR LAB

It's apparent that this technology makes for a good marriage between practitioner and laboratory. Mastroianna notes that topography is a great tool for consulting with practitioners when designing a contact lens because both the lab and the practitioner can review the data simultaneously. "The entire exam can be sent over the Internet to allow the laboratory to aid in lens design using its own software," Dr. Buscemi said.

THE BOTTOM LINE

Corneal topography can mathematically define the shape of the cornea better than it has ever been defined before, and since today's computerized manufacturing can accurately recreate any shape the topographer defines, RGP lens quality continues to improve, according to Mark Parker, director of manufacturing and inventory control for X-Cel Contacts. "This means the term 'custom fit RGPs' can actually be achieved rather than merely talked about in marketing terms," Parker said. CLS

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