case study

Corneal Reshaping Lenses for a Pediatric Patient

The insertion of corneal-reshaping contact lenses enabled this seven-year-old to thrive.

BARBARA ANAN KOGAN, O.D., Washington, D.C. AND LARRY B. WALLACE, O.D., Ithaca, N.Y.

A seven-year-old white female presented complaining of blurry distance vision. Past ocular history revealed no previous prescription, and her family history was unremarkable.

Exam findings

Visual acuity (VA) was 20/100 O.U. Refraction revealed -1.50D O.U. with 20/20 distance VA. Phoria testing showed an esophoria of four at distance and near. Vergence measurement revealed an abduction, or divergence, of 11/0 O.U. Adduction, or convergence, was 10/4. Positive relative accommodation (PRA) showed -1.25D O.D. and -0.50D O.S., while her negative relative accommodation (NRA) was 3.50D O.D. and 3.00D O.S. The patient's corneal curvatures were 4500/4625 O.D. and 45.25/4600 O.S.

Diagnosis

Given her slight tendency to over converge at distance, her -1.50D O.U. refractive error and her constricted near visual fields, which are often associated with early and progressive myopia, the diagnoses were esophoria and myopia.

Corneal topography shows data for a similarly aged female (age nine) post-fit of the Contex OK-E lens, the lens in which this patient was fit.

Discussion

When young myopic patients present, we naturally discuss the benefits of distance spectacles. What some of us tend to forget or overlook, however, is that this option can often make childhood activities, such as sports, difficult, decrease self-esteem and lead to bullying.¹ As a result, some practitioners offer young patients corneal-reshaping (CR) contact lenses — devices that have been found to have a corrective and preventive/control effect in childhood myopia.²

CR lenses, also known as orthokeratology, first gained recognition in the 1960s, when George Jessen, a Chicago O.D., used a gas permeable (GP) contact lens to alter refractive error. He called the technique "Orthofocus."³

The scientific community, however, resisted the validity of CR for more than 20 years because they suspected that changing the cornea's shape was dangerous.³ It seems their concerns were warranted, as early CR lens designs were simply standard lenses that were fit progressively flatter over a period of time. The result: flat-fitting creations that often de-centered up or down, inducing corneal distortion and increased astigmatism.³

To correct this problem, Nick Stoyan (one of the early pioneers of CR) and colleagues created and patented "reverse geometry" designs, which employed three individual zones to provide a more controlled and deep flattening of the central cornea, than their predecessors, while decreasing the time to achieve myopia reduction.³ The results: The designs provided better control of lens centration than the previous offerings, though patients were less than thrilled with the three- to six-month treatment time to achieve a maximum myopic reduction of 2.00D to 3.00D.³

Since then, the Food & Drug Administration (FDA) has approved two families of overnight CR lenses: Corneal Refractive Therapy (CRT) from Paragon Vision Sciences in 2002, and Vision Shaping Treatment, from Bausch & Lomb in 2005. Despite these approvals, however, many practitioners have opted to stick with their previous lens choices.

Research has implicated CR lenses in corneal higher-order aberrations, an increase of corneal astigmatism and corneal iron ring (as the result of the fitting curve of the reverse-geometry lens).^4-9 Higher-order aberrations are not necessarily adverse here, as spherical aberration is one of the mechanisms for controlling myopia. You can offset corneal astigmatism via proper patient selection (less than 1.50D of with-the-rule astigmatism or by lens-parameter changes post fit).

CR lenses have also been implicated in microbial keratitis (pseudomonas aeruginosa and acanthamoeba spp.), central corneal epitheliopathy lesions, corneal-pigmented arc, microbial flora of the tears, corneal infiltrates, toxic keratitis and lens-binding.^10-15

Because non-compliance has been linked with the development of microbial keratitis and flora in CR lens-wearers, and young children are deemed not as hygienic and/or as responsible as adolescents and adults in complying with the prescribed contact lens-wear and care regimen, many practitioners don't offer CR lenses to this population.^11,14 Obviously, the primary fear for the practitioner is the induction of vision loss, though many practitioners are, no doubt, just as concerned about malpractice law-suits, should such complications arise from these lenses.

Research has shown, however, that we can minimize the aforementioned risks by educating this young population and their parents on the importance of complying with our directions and having parents sign an informed-consent document.^16-20

Management

After this patient's parents described their daughter as "responsible" and "neat" and assured me they were committed to helping her obtain the best vision anyway they could, I offered the patient a CR lens. I immediately told the family, however, that the success of the device depended on their commitment to following my directions on lens-care and wear. Then, I explained my reasons for my directions and had the patient and her parents sign a contract that outlined the procedure and our individual roles in the process.

I asked the patient to return for weekly follow-up visits, so I could check the health status of her eyes and conduct one-hour vision-therapy sessions for her esophoria. She complied.

I last saw this patient six months ago. She has achieved 20/20 VA O.U. unaided, her myopia has not worsened, and her eyes are healthy. She continues to wear her lenses overnight six times a week. On night seven, she takes a break with no resulting loss of acuity. OM

References furnished upon request.

Dr. Kogan, a former orthokeratology specialist, has written and lectured extensively on orthokeratology since 1991.

Dr. Wallace has been president of The college of Syntonic Optometry as well as the director of education since 1995. He has been in private practice in Ithaca, N.Y. for 30 years.