The Benefits of Oxygen Permeable Contact Lenses
New FDA-approved GP lenses offer niche opportunities in patient care and practice management.
BY BARBARA ANAN KOGAN, O.D.
Today's gas permeable (GP) lenses are prescribed for vision needs ranging from routine myopia to accelerated orthokeratology for crisp, unaided acuity during waking hours. And GP lens manufacturers continue to improve specialty lens designs for
keratoconus, post-surgical applications and high amounts of astigmatism.
Lee Dickerson, secretary/treasurer of the Contact Lens Manufacturers Association
(CLMA), represents the association's member labs. With 16 years as president and co-owner of ABBA Optical and 32 years' total contact lens experience, he suggests that you think of GPs as "offering patients a safer ocular environment and a wider range of products with greater profit potential than hydrophilic lenses for the practitioner." Here's what you should know about these lenses along with a description of the GP lenses approved by the Food and Drug Administration (FDA) since October 2001.
ILLUSTRATION BY ANTHONY
New bifocal GPs
The presbyopic population is the most rapidly expanding segment of the eyecare market. Recognizing this opportunity, CLMA members, working independently, have developed a wide array of
multifocals, bifocals and trifocals for emerging-to-advanced presbyopes and also for patients who have large amounts of astigmatism. Per-patient cost-of-goods sold range from about $100 to $230. Fees range from $450 to $800, and doctors realize about $350 to $570 in profit.
Here's a run down on individual bifocal lenses that received recent FDA approval.
Custom Eyes bifocal by ABBA. Available since October 2001, this hybrid bifocal combines the progressive features of aspheric lenses with the sharp acuity of spherical lenses. This translating bifocal GP is available for early, moderate and advanced presbyopes with up to a +3.50D add. It provides good mid-zone vision (especially for computer work) because it has no center segment line.
MagniClear plus by Art Optical Contact Lens, Inc.
The FDA approved Art Optical's newest GP bifocal lens in March 2002. Mike Johnson,
F.C.L.S.A., and director of consultation services for Art Optical, explains, "The MagniClear plus lens was specifically brought out for the presbyope who is 50 years or older and needs an add from a +2.25 to a +6.00 to provide good distance and near acuity."
The following are some new contenders who've appeared in the specialty GP lens market and have received FDA approval over the past year.
Intra-Limbal by Lens Dynamics. In April, 2002, the FDA granted Lens Dynamics approval to manufacture this GP lens for patients who have:
- highly asymmetric corneas
- pellucid marginal degener ation
- keratoconus with an inferior apex
- had a penetrating keratoplasty.
Lens Dynamics President and CLMA Board Member Al
Vaske, N.C.L.C., says, "This standard 11.2 overall diameter GP, worn inside the limbal area, is designed to achieve .1 mm to .2 mm of movement without infringing on the
limbus." The Dyna Intra-Limbal's easy-to-fit 14 lens fitting set in Boston's XO material has detailed fitting guidelines for each type of irregular cornea.
Menicon Z by Menicon Co., Ltd.
Carl Moore, F.C.L.S.A., past CLMA president and president of Con-Cise Contact Lens Company for 43 years, received the exclusive right to manufacture Japan's Menicon GP lenses at the beginning of the Q4 2001.
At the beginning of Q3 2002, the FDA approved Menicon's application to market its Menicon Z GP contact lens for up to 30 days of continuous wear. This was a first for a GP contact lens and for a Japanese developer and manufacturer.
Moore, who also serves as chair of the CLMA's RGP Lens committee, cites Menicon Z's high Dk of 163 as "one that also provides a high degree of confidence in ocular health following continuous wear of a GP contact lens." He notes that the next highest Dk for GP lenses is 100.
The Menicon Z lens maintains ocular health and, according to its continuous wear approval, can be worn in spherical, aspheric, custom toric and multifocal designs.
In the real world
How do these lenses perform in practice? John Ray,
O.D., of Lansdale, Pa., has 5 years of experience fitting bifocal lenses on 300 to 400 patients. He says, "Custom Eyes works from early to advanced presbyopia and for when a patient's near vision requirements are above average (such as seeing sutures or jewelry though a loop). This lens provides exceptional near vision."
A significant advantage of the MagniClear plus bifocal, according to Gary Anderson,
O.D., of Grand Rapids, Mich., is "its ability to keep its well-centered, spherical and back toric design for existing GP wearers. You're not limited by the base curve or overall diameter."
RGP versus GP
At the Contact Lens Manufacturers Association's spring 2002 board meeting, members agreed to delete the word "rigid" from the term "rigid gas permeable"
(RGP) and instead use the term "gas permeable" (GP).
The Dyna Intra-Limbal differs from other GP lenses for irregular corneas because "it's diameter is larger than most corneal lenses, but not quite as large as a scleral lens, and it maintains an intracorneal position," says Shelley I. Cutler,
O.D., of Lower Gwynedd, Pa.
"I can see the Menicon Z as a niche lens in my practice, especially for patients who have a corneal cylinder of more than 0.75D," says Mike
Gzik, F.C.L.S.A., of Syracuse, N.Y. "The lens needs to have good movement, good
centration, good visual acuity and provide the same physiology as a daily wear lens," he adds.
Try them, you'll like them
Today's GP contact lenses have a lot to offer. Along with the visual acuity they offer patients, most of them have a delivery time of 24 to 48 hours after the order, with or without lab consultation. And proficiency with them can help you set your practice apart from the crowd.
Dr. Kogan has authored nearly 50 contact lens articles since 1983. She frequently prescribed bifocal and specialty GPs in her downtown Washington, D.C. practice for 13 years and relied on lab consultation for successful fitting. She's been wearing GPs since their FDA approval more than 20 years ago and wore PMMA contact lenses for 15 years before that.
GP Educational Opportunities
O.D., MSEd, University of Missouri at St. Louis School of Optometry director of Student Affairs and executive director of the CLMA's educational division (the RGP Lens Institute
[RGPLI]), suggests that practitioners at all levels of GP experience participate in the RGPLI monthly online symposia. Scheduled for the second Tuesday of each month from
8:00 p.m. to 9:30 p.m. (Central Standard Time), the topics include:
- GP bifocal fitting and problem solving
- GPs for the irregular cornea and for young people
- practice management.
Dr. Bennett selects experts in each category as faculty for the symposia, which he describes as "offering healthy discussion pertaining to specific GP designs and multiple options."
"You can register under any name to join the chat and have the option to observe or participate with other chat attendees, as well as ask the symposia faculty questions," Dr. Bennett says. Online symposia are one of the many RGPLI resources for enhancing your education. They frequently feature case studies.
For more information about the
RGPLI, call (800) 344-9060.
Dr. Kogan has authored nearly 50 contact lens articles. She frequently prescribed bifocal and specialty GPs in her downtown Washington, D.C. practice for 13 years and relied on lab consultation for successful fitting. She's been wearing GPs since their FDA approval more than 20 years ago and wore PMMA lenses for 15 years before that.
Optometric Management covered the GP lenses approved by the FDA in 2001 in our October 2001 issue ("What's New in
RGPs?" page 59). The feature includes information on the HDS 100 bifocal, Blanchard's Essential RGP bifocal, the Mandall Seamless bifocal, Art Optical's Magni Clear bifocal, Lens Dynamics' Presbylite bifocal, and Specialty Ultravision's
Epicon. It is also available on the OM Web site at www.optometric.com/archive_results.asp?article=70286&iss=10/1/01.
Optometric Management, Issue: October 2002