Orthokeratology
Orthokeratology, or corneal refractive therapy, refers to the overnight use of RGP contact lenses to temporarily reduce myopia. The goal of this nonsurgical method of temporary myopia reduction is to achieve functional UCVA during the day. The contact lens is fitted at a base curve that is flatter than the corneal curvature. Temporary corneal flattening results from the flattening of corneal epithelium. Use of the lens is intended for the temporary reduction of naturally occurring myopia between –0.50 and –6.00 D of sphere, with up to 1.75 D of astigmatism.
Orthokeratology is most appropriate for highly motivated patients with low myopia who do not want refractive surgery but who want to avoid use of contact lenses and glasses during the day. These contact lenses do not treat astigmatism or hyperopia. Prospective patients should be informed that in clinical trials, approximately one-third of patients discontinued contact lens use, and most patients (75%) experienced discomfort at some point during contact lens wear. Complications of orthokeratology include induced astigmatism, induced higher-order aberrations, recurrent erosions, and infectious keratitis. Infectious keratitis—the most serious complication—can be bilateral and seems to be more common in children and teenagers. Pathogens implicated include Pseudomonas, Acanthamoeba, Staphylococcus, and Nocardia species.
The prevalence and incidence of complications associated with orthokeratology, such as bacterial and parasitic keratitis, have not been determined. Sufficiently large, well-designed, controlled studies are needed to provide a more reliable measure of the risks of treatment and to identify risk factors for complications. See BCSC Section 3, Clinical Optics, for further discussion of orthokeratology.
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Berntsen DA, Barr JT, Mitchell GL. The effect of overnight contact lens corneal reshaping on higher-order aberrations and best-corrected visual acuity. Optom Vis Sci. 2005;82(6): 490–497.
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Mascai MS. Corneal ulcers in two children wearing Paragon corneal refractive therapy lenses. Eye Contact Lens. 2005;31(1):9–11.
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Premarket Approval. Paragon CRT. PMA P870024/S043. US Food and Drug Administration website. Updated November 7, 2016. Available at https://goo.gl/7sOAnM. Accessed November 7, 2016.
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Saviola JF. The current FDA view on overnight orthokeratology: how we got here and where we are going. Cornea. 2005;24(7):770–771.
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Schein OD. Microbial keratitis associated with overnight orthokeratology: what we need to know. Cornea. 2005;24(7):767–769.
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Van Meter WS, Musch DC, Jacobs DS, et al. Safety of overnight orthokeratology for myopia: a report by the American Academy of Ophthalmology. Ophthalmology. 2008;115(12): 2301–2313.
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Watt K, Swarbrick HA. Microbial keratitis in overnight orthokeratology: review of the first 50 cases. Eye Contact Lens. 2005;31(5):201–208.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.