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Overnight ortho-K study shows promising results with low levels of myopia
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SAN FRANCISCO — Although not approved by the Food and Drug Administration (FDA) for overnight use, a prospective study of the effects of overnight orthokeratology (ortho-K) lenses was presented at the recent American Academy of Optometry (AAO) meeting here. The ongoing study, which involves eight subjects, comes on the heels of an FDA notification letter cautioning practitioners about the unapproved use of ortho-K lenses for overnight wear.
This twist on contact lens wear provides yet another option for patients wanting freedom from correctable lenses — at least temporarily — without choosing surgery. Ortho-K, the temporary treatment of refractive error by the application of rigid contact lenses designed to re-shape the cornea, has been practiced in the United States for more than 30 years.
The OK lens from Contex Inc., of Sherman Oaks, Calif., became the first ortho-K lens to receive FDA approval in April of last year. The notification letter the FDA distributed late last year served a dual purpose: to caution practitioners against possible effects of unapproved use of ortho-K lenses as well as to amass further information on these types of lenses for the FDA itself.
Mark A. Bullimore, MCOptom, PhD, of The Ohio State University College of Optometry, thinks that overnight ortho-K wear is definitely worth researching. “The attractive aspect of overnight ortho-K is this: with the original concept of daytime wear, you had to wear your lenses a fair amount of the time, undermining the goal of the process, which was to be lens-free. If you had to wear your lenses 8 hours a day, what’s the point of wearing an ortho-K lens? With overnight ortho-K, you can sleep in them, take them out in the morning and be free of the lenses all day. That’s a much more attractive option to any patient,” he said.
Prospective study results
This idea is the basis of the study that Dr. Bullimore and his colleagues presented at the AAO meeting. To be included in the study, the subjects were required to have spherical refractive errors between –0.50 and –3.50 D; cylindrical refractive error of less than or equal to –1.00 D; keratometry readings greater than 41.00 D in the flatter meridian; and the absence of any ocular disease.
After being fit with their ortho-K lenses, the subjects were instructed to wear them overnight only for a 60-day period, during which their progress was monitored on day 1, day 7, day 14, day 30 and day 60. Surprisingly, Dr. Bullimore reported, the wearing schedule seemed to reach its maximum effectiveness after only 7 days. “The effects seemed to be remarkably self-sustained throughout the workday,” he said. He also noted that research, notably that of Helen Swarbrick, PhD, FAAO (see Primary Care Optometry News, “Researchers find orthokeratology changes epithelial, stromal thickness,” October 1998, page 21) suggests that the lens may re-distribute the corneal epithelium rather than re-shape the entire cornea as is typically thought. “It makes sense from a common sense perspective,” he said. “It’s much more likely that a rigid lens is smudging epithelium around rather than producing a change in a rigid collagen structure, which is basically what the stroma is.”
Best for lower levels of myopia
Dr. Bullimore said that ortho-K is most effective in people with lower levels of myopia. “We had success up to 3 D, but our mean effect was –1.75 D,” he noted.
He said that the data reporting how long it takes the refractive error to return have not yet been analyzed, but seemed to vary among the subjects. “When some people stopped wearing the lenses, all of a sudden they were back to where they started,” he said. “For other people, there was still a partial residual effect after 2 or 3 weeks.”
If and when the FDA approves the use of ortho-K lenses for overnight wear, studies like Dr. Bullimore’s should serve as a valuable tool. At least two companies are developing ortho-K lenses intended for overnight wear.
For Your Information:
- Mark A. Bullimore, MCOptom, PhD, may be reached at The Ohio State University College of Optometry, 338 West 10th Ave., Columbus, OH 43210; (614) 292-4724; fax: (614) 292-4949; e-mail: bullimore.1@osu.edu. Dr. Bullimore has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.