The use of overnight corneal reshaping with contact lenses for the temporary reduction of myopia was FDA approved in June 2002. Since its approval, an estimated 5,000 U.S. practitioners specialize in the use of these lenses.¹ But the adoption rate outside the U.S. has exceeded the rapidly-growing U.S. rate in recent years; there is a greater prevalence of myopia in the Asia-Pacific Rim.² The increase in the adoption and practice of this specialty is also fueled by the growing evidence of the effectiveness of corneal reshaping in regulating the development of myopia.^3,4 Recent advances in lens design and clinical practice show an increased effectiveness for higher amounts of astigmatism and the temporary reduction of hyperopic refractive errors.

A Global Perspective
A Global View of Specialty GP Lenses report indicates significant growth in the corneal refractive therapy market internationally with wide regional variance.² One factor is the difference in the regulatory control of corneal reshaping from country to country. While the predominant purpose in recommending the treatment in North America and Asia today is myopia control in children and adolescents, adults make up the majority of fits in most European countries.^2,5

When corneal reshaping was introduced in the Netherlands in 2002, fitters were required to have an on-site topographer and to complete a training course before prescribing the lenses.⁶ In the U.S., the FDA required training and certification. Training courses were provided at meetings or online and certification was required before a practitioner could order lenses. In China, however, lenses could be purchased from unlicensed vendors with no credentials or training documentation. Japan’s regulatory body required an extensive five-year data collection study before approving corneal reshaping; the final approval was for patients over the age of 18. The first U.S. FDA approval for overnight corneal reshaping was for paflufocon B and D (Paragon CRT, Paragon Vision Sciences) and no age restrictions were placed on its labeling indication.

• United States: Corneal reshaping, pioneered by optometrists, began as contact lens specialty in the United States over 40 years ago. In the late 1990s, when the specialty first appeared in Asia and Europe, there was a lack of interest by U.S. ophthalmologists. Today, optometry does not even exist in some European and Asian countries and, as a field, suffers from medical-political disadvantages. However, optometry remains well-established in North America. The passing of National Board and State Board exams assures that graduates from U.S. institutions have a minimum standard in their knowledge, skill level and ability. This is not always the case in the rest of the world, including Europe, where each country may have a different level of optometric training and assessment of competency. The practice of corneal reshaping in a given country appears to correlate with the respective state of optometry.

• Europe: This correlation is apparent in France, with one of the lowest percentages of new corneal reshaping fits in Europe.⁷ France has no educational and regulatory framework for optometrists. In contrast, in the strong eyecare community of the Netherlands, the prevalence of corneal reshaping therapy is greater than any country in Europe.^5,6

In Germany, where optometry is nonexistent, motor vehicle regulations require drivers who utilize contact lens corneal reshaping to have their visual acuity checked every three months to maintain driving privileges; post-LASIK drivers require no such follow up. In contrast, those who practice corneal reshaping in Italy have an active organization that conducts annual educational meetings and boasts an excellent fellowship program. The Netherlands also has a strong contact lens society, which holds an educational conference (NCCL) that drew 1,500 mostly local attendees in 2010. Similarly, the British Contact Lens Association provides an expanding curriculum of corneal reshaping education as part of its annual meeting. While the European Union is large and influential in the world community, it has been fragmented in its application of corneal refractive therapy due to political, regulatory and educational differences.

• Asia-Pacific Rim: The Asia-Pacific Rim countries suffered from the absence of regulation and enforcement of health care delivery policies. China, in the late 1990s, had minimal regulation for corneal reshaping and had a number of cases of microbial keratitis in its adolescent population reportedly secondary to wearing overnight corneal reshaping lenses. In response to the reports, the government prohibited the practice of corneal reshaping until it could be properly regulated. In 2007, the first corneal reshaping product received approval by the Chinese regulatory body.⁸ The hiatus allowed for careful evaluation and planning in the region and facilitated a safe reintroduction of the practice in China.
There have been regulatory approvals in Japan, Korea and Taiwan in the last several years. China, with more than 50% of its population manifesting myopia, will continue to work toward myopia control with corneal reshaping and other new technologies.^9,10 Recently, the regulatory body in China has expressed interest to expand the indication in their regulatory approval for patients under the age of 18.

• Australia and New Zealand: Practitioners and researchers in Australia embraced corneal reshaping early and have invested in advancing the technology. The Research in Orthokeratology group, founded in 2002, has focused on the need for basic research in the field. Research has included the mechanisms of corneal reshaping and the safety and efficacy of corneal reshaping for myopia control. The Oceania Society made up of practitioners from New Zealand and Australia holds comprehensive annual educational events on the latest in corneal reshaping.
Corneal reshaping internationally is at a crossroads. The acceptance by ophthalmology—which is the dominant eye care delivery profession in a number of European and Asian countries—was a turning point. Further, since most of the current worldwide organizations with interest in corneal reshaping are small in number and lack coordination, a united international entity is envisioned. This month, groups from Asia, the Americas and Europe will come together at the Vision By Design meeting in Orlando, Fla. to form an international organization. The first corneal reshaping educational events are scheduled for Europe in Fall 2011 and Asia in 2012.

Refractive Error Regulation
The growing body of science supporting the role of peripheral hyperopic defocus in the growth in axial length in myopia, along with the apparent effectiveness of corneal refractive therapy in modulating the defocus, has stimulated a growing number of practitioners to recommend corneal refractive therapy (CRT) for myopia regulation. Fortuitously, CRT for myopia results in a zone of curvature in the mid-peripheral cornea, which is shorter in radius than the post-treatment central cornea. This steeper zone causes light to be focused in front of the retina in the mid-periphery, while the central axial light is focused on the fovea.

However, CRT is not the only optical intervention for refractive error regulation. CIBA Vision has licensed the technology for non-corneal reshaping contact lenses for refractive error regulation and Carl Zeiss Vision has licensed the technology for spectacle lenses to control the peripheral defocus. Even so, an increasing number of practitioners worldwide are recommending CRT for refractive error regulation. They deem this to be in their patients’ best interest; the patients garner the benefit of vision correction without spectacle or contact lenses during their waking hours.

Overnight Hyperopia Care
The first reports of the potential for success in the treatment of hyperopia with overnight corneal reshaping were in 2004 and 2005.^11-15 The results of a study by Luigina Sorbara, O.D., M.Sc., at the University of Waterloo showed that the fitting of Paragon CRT for hyperopia has a significant effect on corneal shape and refractive error, supporting the effectiveness of hyperopic CRT.^16,17 While this is an off-label procedure today due to the absence of the indication in the FDA approved labeling for the products, practitioners offer hyperopic treatment. In Paragon CRT, practitioners used the same design as that approved lens for the treatment of myopia. The sigmoidal return zone, unlike reverse geometry designs, automatically reverses when the base curve is steep and the return zone depth is relatively shallow.

This reversal causes the medial aspect of the return zone to become convex to the eye to create a “knee” that assists the movement of corneal tissue inward to result in the central cornea reducing in radius of curvature to match the base curve of the lens. As a result, the central cornea becomes steeper to correct the hyperopia while the mid-peripheral cornea becomes relatively flatter. Interestingly, this causes the eye to have a peripheral hyperopic defocus while the central light is focused on the retina. This suggests that there may be value in regulating of hyperopic refractive error development in children by providing a peripheral hyperopic defocus to stimulate axial length growth to create resultant emmetropia. While animal studies suggest that peripheral defocus in hyperopic refractive error regulation operates in the same manner as myopic regulation, there have not been any studies presented to support the phenomena in humans after corneal reshaping.^3,4,18,19

Advancements in Astigmatism
Paragon Vision Sciences launched the dual axis design as an extension of Paragon CRT. The intention of the design was to improve lens centration on eyes having corneal cylinder. In a standard design, the lens would first contact the flat meridian and would at times decenter due to the elevation difference between the flat and steep meridians in the periphery of the cornea. The design has a spherical base curve with a peripheral system, which allows the two orthogonal meridians to have a depth that is different from each other. The depth of the return zone in the two meridians can be modulated as well as the angle of the landing zone in the two meridians. The most frequently prescribed dual axis lenses have a 50µ difference in the return zone depth with no difference in the landing zone angles.¹

While the design of the return zone and the landing zone is not a torus, it can be understood in a similar way. Practitioners use the elevation plot provided by their corneal topographer to determine the need for the dual axis design. The design is recommended when the elevation difference between the two meridians at a chord of 8mm is greater than 25µ. The FDA approval for Paragon CRT includes myopia up to 6.00D with and without astigmatism up to 1.75D. Practitioners are reporting greater accuracy in treating astigmatism up to the limit of approval. Cases have been presented of treatment of as much as 3.00D of astigmatism.²⁰

Overnight Corneal Reshaping
Though corneal reshaping dates back more than four decades, much of the data used to substantiate safety and efficacy of the procedure are anecdotal. Understandable questions arose about safety of the modality from reports of injury and vision loss related to the treatment. To answer these questions, a review of the literature was conducted to report the total number of infectious keratitis cases secondary to corneal reshaping and the causative agents worldwide.²¹ The results of this research showed that the majority of these cases occurred around 2001 and a significant causative agent was Acanthamoeba. It could not be determined from the literature if the lenses worn by the affected adolescents were corneal reshaping designs and the material of the lenses involved was not reported.

Today there is a preponderance of evidence to support the conclusion that corneal reshaping lenses worn according to their labeled indications, recommended fitting and patient instructions are safe and efficacious. A number of studies have been conducted that address the safety of corneal reshaping including the Children’s Overnight Orthokeratology Investigation (COOKI), Longitudinal Orthokeratology Research in Children (LORIC), Corneal Reshaping And Yearly Observation Of Nearsightedness (CRAYON), Stabilizing Myopia by Accelerating Reshaping Technique (SMART), Overnight Corneal Reshaping (OCR), Myopia Control With Orthokeratology Contact Lenses in Spain (MCOS), Role of Corneal Reshaping In Myopia Control (ROMIO), Toric Orthokeratology-Slowing Eye Elongation (TO-SEE), High Myopia-Partial Reduction Orthokeratology (HM-PRO) and a retrospective safety study conducted at The Ohio State University.^{3,18,19,22-25} Here are the results of these studies:

• Results from the COOKI and CRAYON studies suggest that 75% of children are capable of wearing corneal reshaping lenses.²⁶
• The MCOS study concluded that, “the incidence of adverse events found with OK in MCOS is higher than that reported with RGPs, but similar to that reported with soft contact lenses (both SiH and Hi).”^18,27
• The SMART study results, revealed at the 2011 Global Specialty Lens Symposium (GSLS), reported that both the test group and the control group of soft contact lens wearers had the same safety findings.^4,28
• ROMIO found only mild grade I peripheral staining in the corneal reshaping test group versus a control group of spectacle wearers.²⁹
• The Ohio State study found that “the risk of MK (microbial keratitits) with overnight reshaping lenses is similar to other overnight modalities.”²² The study was performed at the request of the FDA to address concerns about the safety of overnight wearing of corneal reshaping lenses in children. The researchers obtained data from 86 randomly selected practitioners and 1,317 patients fitted during 2005 and 2006. The patients contributed 2,593 patient years of wear, divided almost evenly between adults and children. Fifty event forms were submitted with 11 reporting corneal infiltrates. Two of these were MK (both adult wearers), resulting in an estimated incidence of 7.7 events per 10,000 years of wear. These data suggest that corneal reshaping patients have a slightly higher risk of developing MK than daily wear soft contact lens wearers. The risk of MK in overnight corneal reshaping wearers may be as high as that for silicone hydrogel lenses worn overnight.^30,31

Future Forecasts
Corneal reshaping lenses do not increase the risk of eye infection any more than wearing contact lenses. This has been demonstrated both in controlled study conditions, and by retrospective data analysis from clinicians fitting these lenses. Most of the above studies fit only subjects who fell within FDA approved labeling for corneal reshaping. Practitioners are encouraged not to deviate from these indications in order to ensure a safe outcome.

The practice of corneal refractive therapy is global and growing. It is driven by the primary benefit of providing the temporary reduction of refractive error to allow useful vision during waking hours, free of spectacle and contact lenses. Recent studies support the safety as equivalent to wearing silicon hydrogel lenses overnight and slightly lower than wearing daily wear soft lenses. The evidence of the possible benefit in regulating refractive error has stimulated additional acceptance for CRT. The application of designs for the temporary treatment of hyperopia and the increased effectiveness for refractive errors with greater amounts of astigmatism are forecast to expand the number of patients who can benefit from CRT.

The correlation of the strong modality where optometry is established may indicate a medical-political bias. We forecast a continued acceptance of the modality in both ophthalmology and optometry. This is expected to be supported by regulatory practices that are more stringent in training and certification, along with expanded labeling to indicate the modality for juveniles where it is presently only indicated for adults. What we need now is an international organization to serve as an educational forum and to provide advocacy for the modality is forecast to support future growth. Once formed, it will support the successful standard of care and reduce the medical-political barriers. 

Dr. Cary M. Herzberg is a 35 year veteran of the optometry field. He is the founder, president, a board member, and a fellow of the Orthokeratology Academy of America.

Dr. Legerton is an author, lecturer, inventor and consultant to the ophthalmic industry. The former managing partner of a San Diego practice, he was the co-founder of SynergEyes and has 24 issued U.S. patents.

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