RGPs
What's New in RGPs?
Advances in manufacturing and new lens designs are creating easier-to-fit, highly customized lenses.
By Barbara Anan Kogan, O.D.

Over the past year or so, we've seen some niche areas of rigid gas permeable (RGP) contact lenses expanding, mainly for two reasons. First, practitioners are demanding more customized lenses, and second, labs are more capable than ever of designing specialty RGPs -- especially for patients who need multifocals, or need lenses following refractive surgery and for patients who have keratoconus. These niche areas are expanding where soft lens materials aren't feasible or patients have dry eyes.

Advances in technology

According to Ed Bennett, O.D., M.S.Ed., F.A.A.O., executive director of the RGP Lens Institute (RGPLI), a survey he conducted of some member labs of the Contact Lens Manufacturers Association (CLMA) revealed several advances in manufacturing technology that have resulted in better RGP production. These include the following:

• Computer numerically controlled (CNC) lathes have improved RGP reproducibility. Also, newly manufactured lenses need less polishing and lens curves are automated.
• S-form lathing technology, a type of aspheric technology, has resulted in improved presbyopic RGP product application.
• Manufacturing lenses with higher Dks is now possible because of lathing technology that has enabled improved quality of optical surfaces.
• Better edge production machinery enables improved RGP comfort for patients.

With these advances in mind, let's look at new RGPs, plus a line-up of new lens care options.

A look at the lenses

Paragon added the HDS 100 this summer to its HDS family. With a Dk of 100, this lens material received FDA approval for up to 7 days of wear and for use in corneal refractive therapy. It can be used for patients when oxygen permeability is the highest concern. The HDS 100 boasts the highest percentage of methylmethacrylate to provide both excellent wettability and comfort.

"The recent U.S. introduction of Boston's XO RGP contact lens, following its European popularity, provides another 100 Dk RGP lens with very good wettability," comments Larry Brumbaugh, director of sales, market- ing and professional relations at Gaithersburg, Maryland's, Corneal Design. He finds practitioners are "opting for this lens for post laser-assisted in situ keratomileusis (LASIK) patients because of its high Dk, too.

"Bifocals are driving the RGP market up by 30%, and we're seeing an increase in executive bifocal designs that provide a full field of view, compared with an aspheric design," he adds.

Getting help from your lab

Better communication between the practitioner and the lab is increasing fitting success rates. Take the example of Blanchard's Essential RGP bifocal, which is fit intrapalpebrally.

Mr. Brumbaugh offers this advice for a better success rate and for solving problems with this RGP lens and others: "Instill fluorescein into the eye and call the lab's consultant while the patient is behind the slit lamp." A special diagnostic Wratten filter for the slit lamp may be necessary to better describe the fluorescein pattern and a Burton lamp will help with an evaluation, he adds.

"Our lab reproducibility has been enhanced by a new astigmatic lathe that allows us to have numerically controlled computerized manufacturing," Mr. Brumbaugh says. This will enable Corneal Design to meet an "increasing demand for bitoric RGP designs, and we can improve overall consistency of polishing torics and all lenses."

Other new bifocals

Mandell Seamless bifocal. Since the late 1960s, Bob Mandell, O.D., Ph.D., F.A.A.O., has been a bifocal design pioneer and Con-Cise consultant. He received a patent for this lens last spring.

"This bifocal provides a no-jump transition between the distance and near optic zones," says Carl Moore, past CLMA president and current RGPLI chair and president of Con-Cise.

He further explains that Mandell's lens is a "translating bifocal without prism, and the bifocal optics are on the front of the lens." It's manufactured in Boston ES or EO materials from + to -20.00D with true add powers of up to +3.00D. "It's customarily fit slightly larger with overall diameters of 9.6 mm to 10 mm," comments Mr. Moore.

Magni Clear. Art Optical's Director of Consultation Services, Mike Johnson, describes this lens, which is a semi-simultaneous bifocal RGP with 7-mm distance and 0.5-mm intermediate zones and a translating full near zone in the periphery.

"There's no fitting guide for this lens because it's fit like any other RGP," he explains. Parameters for the Magni Clear include bitoric designs to unlimited add powers in 0.25D steps.

He adds, "Magni Clear has front surface optics. We often use the Boston EO material because the lens has a high Dk of 58."

Presbylite. Lakewood, Colorado's, Lens Dynamics manufactures RGPs for the conven- tional presbyopic market and patients who have compromised corneas. Presbylite, the company's translating, segmented RGP bifocal was introduced in the U.S. market last January.

"This lens isn't for the beginning presbyope, but for someone who usually needs a +2.00 to +3.00 add," says Lens Dynamics' President and CLMA board member Al Vaske.

Computer users can benefit from the lens as well because all of the optics are on the front of the lens. Presbylite is a thin, non-truncated lens that "provides comfort and visual clarity for both myopes and hyperopes from +20.0D to -20.D distance parameters," says Mr. Vaske.

The most unique design aspect is the lens's use of an isosceles triangle. It contains a small aspheric intermediate area at the top, and the near-zone sector comprises the balance of the triangle. The lens is manufactured in the Boston ES or EO material.

"We're also awaiting FDA approval on our Rose K2 keratoconus lens," says Mr. Vaske.

Prior FDA approval was granted in 1995 for the Rose K RGP. According to Mr. Vaske, the Rose K2 lens has improved optics and it controls the spherical aberration, photophobia and glare from keratoconus."

Practitioner pearls

After reviewing new lens technology, I find that it's also helpful to get a sense of how successful practitioners are fitting RGPs for all types of patient needs.

RGPs for children. "I'm pushing a lot harder with "kid fits" to contain their nearsightedness, and I routinely fit kids under age 10," says Robert Reed, O.D., St. Joseph, Mich. "However, I make sure they have some maturity before fitting them."

This 22-year practitioner describes the impact of topography as enabling him to fit RGPs better but, he stresses the importance of having a good contact lens lab consultant.

Los Osos, Calif., optometrist, Gary Englund uses the Boston EO Thinsite as his lens of choice for kids because "the edge is really thin and comfortable."

Bifocal RGPs. "Use an aspheric bifocal on a medium to high add," suggests Des Moines' Dave Hansen, O.D. As a participant in Blanchard Lab's bifocal study group, he finds their Essential III RGP good for patients with large pupils.

"This bifocal contact lens gives options for clear visual acuity at near, mid and distance ranges," says Dr. Hansen. The S-form technology of this Boston XO material provides added plus power on the front of the lens in up to a +2.75D add.

Lens Dynamics' Presbylite is a thin, comfortable translating bifocal. "Its small trifocal area in the top triangle of the lens provides useful vision," explains Dr. Hansen. "And, it's more forgiving with varying pupil sizes. Conduct a trial bifocal contact lens fitting for confidence in the final prescription," he suggests.

Excellent solutions for RGP bifocal designs, according to Walter Choate, O.D., F.A.A.O., Madison, Tenn., include a translating lens. He favors Lens Dynamics Presbylite which has an "intermediate that can be used with computer patients and provides up to a +2.75 add for mature presbyopes." This lens is also a good choice for current RGP wearers who are now emerging presbyopes.

"Con-Cise makes an excellent standard tri-curve design with its Mandell Seamless bifocal," says Dr. Choate. "This concentric RGP bifocal is fit the same as a single vision RGP," he adds.

Dr. Choate's recommendation for an aspheric RGP bifocal is Blanchard's three series Essential for the patient who needs adds from +1.25 to +2.75. His emerging presbyopic aspheric lens of choice is Boston's Multivision.

"I choose Art Optical's Magni Clear for new bifocal RGP wearers because it offers clarity in all three distances -- far, intermediate and near," says Dr. Reed.

Dr. Englund says, "I've never missed when prescribing a Carter RGP bifocal, manufactured by a small California lab." This lens, which is fit steep like other bifocal RGPs, "has a smiley face that looks like an Ultex spectacle lens and works well with high adds."

Additional RGP custom options. Although Specialty Ultravision's Epicon RGP is primarily for keratoconus patients, Dr. Englund's experience since the lens's February 2000 introduction is, "This lens works with patients who've had eye injur-ies." He also has success with moderate and high astigmats whose corneas are >46.00D when he wants an RGP fit versus a soft toric contact lens.

Dr. Englund further explains that the Epicon's 13.8-mm diameter makes this a scleral lens and "patients find it's a comfortable lens that works wonderfully for 3.00D of cylinder."

Embracing RGPs

As you can see, we have a lot that's new to choose from when selecting RGPs, and as technology progresses -- with manufacturing and materials -- fitting these specialized lenses will only get easier.

Barbara Anan Kogan, O.D., has published more than 50 of her 225 articles on contact lenses. This former 13-year Washington, D.C., doctor attributes her high success with RGP prescriptions in all modalities to lab consultants and her own experience wearing RGPs since 1981.