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The Latest Lenses for Corneal Reshaping
Manufacturers strive to deliver the best designs.
By Barbara Anan Kogan, O.D.

Results of the Contact Lens and Progression of Myopia (CLAMP) study¹ concluded GP lenses resulted in a slower rate of progression of myopia compared with soft contact lenses, with GP wearers increasing 1.56D (.52 D/year) versus soft lens subjects increasing 2.19D (0.73D/year). �With a bottom-line showing a myopia refractive error of 28.8% slower in the GP wearing group, this significant finding can influence your contact lens decision when fitting a young progressive myopic patient,� said Ed Bennett, O.D., M.S. Ed., the executive director the Contact Lens Manufacturers Association�s (CLMA) GP Lens Institute (GPLI).

This demonstrated efficacy in reducing myopia leads to orthokeratology, or corneal reshaping � for why not make the correction as long-lasting as possible and (almost) eliminate the patient�s need for contact lenses? The options at our disposal are only getting better. Overnight corneal reshaping�s place in the eye care practitioner�s arsenal seems assured as the FDA approves additional lenses for the procedure. Manufacturers have new GP lenses to meet the various design needs of your patients, with even more in the pipeline. Following is a run-down of what�s available now and what will be available to you soon.

Overnight options

►Euclid Systems� Emerald ortho-k  (oprifocon A) lens was approved in 2004 for overnight wear. The lenses are made of Boston R Equalens II GP material and feature a Dk of 85. They�re indicated for the reduction of myopia up to 5.00D and astigmatism up to 1.50D. The Emerald is one of the designs approved for use with Bausch & Lomb�s (B&L) Vision Shaping Therapy (VST).

►Contex Inc. has won FDA-approval for its OK Lenses (also as part of B&L�s VST) to be worn for overnight ortho-k. The lenses are made of Boston R Equalens II GP material and feature a Dk of 85. They�re indicated for the reduction of myopia up to 5.00D, and 1.50D of with-the-rule astigmatism and 0.75D of against-the-rule astigmatism.

►C&E GP Specialist�s Fargo and GP Express lenses are approved for Corneal Reshaping Treatment (CRT). The overnight-wear approval allows for correction of up to 6.00D myopia, with or without astigmatism up to 1.75D. Additionally, the company�s Quadra RG and Quadra RG 100 generic lenses, manufactured in Paragon�s HDS (Dk of 58) and HDS 100 (Dk of 100) materials respectively, are approved for Advanced Corneal Reshaping Therapy. They are indicated for the treatment of myopia up to 3.00D and up to 1.50D of astigmatism. Myopia of less than 3.00D requires one pair of lenses, and myopia between 5.00D and 6.00D requires two pairs for treatment.

►Paragon�s Corneal Refractive Therapy (CRT) lenses, the first to win FDA approval for overnight wear, are indicated for up to 6.00D of myopia and up to 1.75D of astigmatism. The lenses are made from the company�s HDS and HDS 100 materials.

►ABBA Optical�s Orison lens is also made of Paragon HDS 100 material, featuring a Dk of 100. It�s indicated for myopic correction from 3.00D to 6.00D, and for up to 1.50D of with-the-rule astigmatism.

Waiting in the wings

Manufacturers are busy trying to give eye care practitioners even more options for overnight corneal reshaping. E&E Optics will present the Vipok trial fitting lens, which uses a subjective spherical equivalent and mean corneal curvature measurements for lens selection. The designer of that lens, Tsaio-Ching Tung, M.D., reports that he has another patented design to address hyperopic correction � a dual geometric ortho-k lens in a reverse design of traditional myopia ortho-k. It features a steeper central optical zone than the central cornea, followed by a flat plateau zone to prevent tissue pile-up in the mid periphery. �A series of additional curves allows for tear circulation and centering,� Dr. Tung said.

Finally, Paragon is currently in clinical trials using the first GP material approved for 30 days of continuous wear, Menicon-Z, for overnight CRT specialty use. Once FDA approved and certified, the company plans to call this siloxanyl styrene and fluoro-methacrylate GP material Paragon-Z-CRT. It has a Dk value of 163. The primary zone�s central base curve provides the mold for the final corneal shape, while its flatter radius facilitates tissue movement. The secondary, sigmoid-shaped curve controls the amount of lens clearance across the cornea. A shallower sigmoid curve in the return zone, which brings the base curve closer to the cornea, results in greater apical clearance. A third zone uses a unique tangent angle to provide a landing zone in the peripheral cornea to maximize patient comfort.

Take the next step

�We encourage you to use a CLMA-member laboratory for more information about corneal reshaping designs, and support with necessary materials for certification,� says newly-elected CLMA president, Dan Bell. CLMA-member laboratories and materials are available at: www.rgpli.info.

References

1. (A Randomized Trial of the effects of Rigid Contact Lenses on Myopia Progression. Walline JJ. Archives of Ophthalmology. Vol 122 (12), p 1760-1766. www.archofophthalmol.com.

Barbara Anan Kogan, O.D., has written and lectured extensively on orthokeratology since 1991 when she began the modality in her contact-lens-only Washington, D.C. practice. Thanks to guidance from ortho-k inventor Dr. Grant, Dr. Wesley�s National Eye Research Foundation and CLMA-member contact lens consultants, 22% of her patients completed a combined ortho-k treatment with vision therapy.