The New Focus for Future Myopia Control
BY MARJORIE J. RAH, OD, PHD
This summer I had the opportunity to attend the Global Orthokeratology Symposium (GOS) in Chicago. I left the meeting knowing that interest in orthokeratology is still strong. If you weren't able to attend the 2005 GOS meeting but are curious about new information on the topic, following is a recap of some of what I learned at the meeting.
Currently, myopia control seems to be one of the hottest "hot topics" when it comes to corneal reshaping contact lenses. Earl Smith III, OD, PhD, discussed the importance of the para-macular retinal tissue and its role in myopia development. According to the information that Dr. Smith presented, myopia can be induced even when the macula has been ablated, leading him to conclude that "the peripheral retina by itself can regulate emmetropization."
Dr. Smith's line of research ties into the research presented on aberrations. Researchers presented data showing the effects of ocular aberrations, most specifically spherical aberration. Both David Berntsen, OD, MS, and John Mountford, Dip. App. Sc, FAAO, FCLSA, FVCO, showed that a significant increase in spherical aberration occurs following ortho-k treatment. Although their data came from adult subjects, I theorize that most likely similar results would occur in younger patients as well. These data correspond to Dr. Smith's data: Spherical aberration can produce blur in the same para-macular or peripheral retinal region. This information is important in determining the mechanism by which orthokeratology may or may not prevent myopia progression.
Researchers also presented preliminary information on clinical studies that specifically investigated myopia progression and orthokeratology. Pauline Cho, BOptom, PhD, presented her results from the Longitudinal Orthokeratology Research in Children (LORIC) Study. Dr. Cho reported persuasive data on changes in axial length. On average, children in the ortho-k group showed less axial growth than those in the historical control group of matched age, gender and refractive error.
The top award in the poster session went to Edward Chow, OD, who presented information regarding refractive status based on axial length change after discontinuation of night wear orthokeratology. The patients had worn the lenses for a minimum of five years prior to discontinuation and were compared to an age- and refractive status-matched control group. Similar to Dr. Cho's data, Dr. Chow's findings showed less axial growth in patients who had undergone orthokeratology treatment.
Still Seeking Answers
Although these studies provide important groundwork regarding myopia control with orthokeratology, I think it's important to realize that we don't have a definitive answer regarding whether ortho-k will slow down or halt the progression of myopia. Future studies are necessary before we can have that answer. In the meantime, I give parents and patients who ask only the facts that I have and I tell them that I don't yet have a final answer to the question.
Dr. Rah is an assistant professor at the New England College of Optometry where she works primarily in the Cornea and Contact Lens Service in patient care, teaching and research.