Do the potential benefits of orthokeratology outweigh its potential infection risks?
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Too risky
I do not believe that the potential benefit of reducing the progression of myopia in children outweighs the risks, which include microbial keratitis.
Most pediatric ophthalmologists are uncomfortable prescribing rigid gas permeable contact lenses in children, let alone for them to sleep with lenses in their eyes at night. The idea of sleeping with the lenses was an attempt to reduce the foreign body sensation that occurred with frequent blinking during the day. I have seen children in my practice present with central subepithelial corneal opacities following prolonged orthokeratology treatment. These may be reversible changes, but I am uncomfortable accepting this sequela in a child. Poor contact lens hygiene in children is another negative to consider. Furthermore, the debate is still on whether the refractive error modification is permanent when treatment is stopped.
Recently, there has been great interest in reducing the progression of myopia by other interventions that may be safer and more practical. A disposable radial refractive gradient (RRG) soft lens has been approved by the FDA to slow the progression of myopia in children. The theory is that progression of myopia with use of standard contact lenses may actually be enhanced by the peripheral image being focused behind the retina because of the curvature of the globe. Simplistically, the axial length of the eye may increase to “reach” this image behind the retina in the process of emmetropization. The concentric peripheral rings in the RRG lens move the peripheral images in front of the retina and potentially reduce the growth of the eye.
For those of us who prefer to stay away from contact lenses in children, we have the option of using off-label low-dose atropine drops daily to attempt to reduce the progression of myopia. Numerous studies have shown this treatment to be of benefit. I am anxiously awaiting the results of the two ongoing FDA drug trials in the U.S. that are studying the pharmacologic reduction of myopia progression in children (PEDIG and CHAMP).
Rudolph S. Wagner, MD, is an OSN Pediatrics/Strabismus Board Member.
Risk is low
Orthokeratology is FDA approved for correcting myopia by using a specialized contact lens overnight to temporarily reshape the corneal curvature, allowing for good vision without need for refractive correction during the day.
Unexpectedly, it was found that these lenses could also affect myopia progression. The exact mechanism for reducing myopia progression is not completely understood but may involve relative myopic defocus on the peripheral retina, leading to stabilization in eye growth and slower axial elongation.
Myopia is now considered a global epidemic. A meta-analysis by Holden and colleagues suggested that by 2050 half the world population may be affected by myopia, with tremendous social and economic burden.
Many modalities have been investigated to slow the progression of myopia, including spectacle lenses, soft contact lenses, rigid gas permeable lenses, antimuscarinic agents and orthokeratology. In a recent Cochrane review including 41 studies, antimuscarinic topical agents, such as atropine, were effective at slowing myopia progression, as was orthokeratology (axial length).
Despite the advantages of topical agents, orthokeratology remains a viable option for myopia control in many children who may not tolerate drops. Patients with greater degrees of myopia and longer axial length benefit more from orthokeratology lenses than those with lower myopia in terms of slower rate of progression of axial length. Orthokeratology may also have synergistic effects when combined with other myopia progression interventions, such as atropine.
The primary risk of orthokeratology is microbial keratitis, which can be potentially blinding, and remains a concern given the pediatric target population for this intervention. However, studies to date suggest that the overall risk remains low, especially in those pediatric patients who are able to maintain appropriate lens hygiene, often with the help of caregivers. In a systematic review analyzing the safety profile of orthokeratology, they reported the incidence of microbial keratitis was 7.7 cases per 10,000 patient-years.
Like all interventions, risk-benefit analysis needs to be reviewed for each individual patient and their family. Orthokeratology should be discussed when reviewing options for myopia control.
- References:
- Cho P, et al. PLos One. 2020;doi:10.1371/journal.pone.0243416.
- Fu AC, et al. Cont Lens Anterior Eye. 2016;doi:10.1016/j.clae.2015.07.006.
- Holden BA, et al. Ophthalmology. 2016;doi:10.1016/j.ophtha.2016.01.006.
- Lee YC, et al. BMC Ophthalmol. 2017;doi:10.1186/s12886-017-0639-4.
- Liu YM, et al. Eye Contact Lens. 2016;doi:10.1097/ICL.0000000000000219.
- Sánchez-Gonzáez MC, et al. J Clin Med. 2020;doi:10.3390/jcm9082371.
- Vagge A, et al. Diseases. 2018;doi:10.3390/diseases6040092.
- Walline JJ, et al. Cochrane Database Syst Rev. 2011;doi:10.1002/14651858.CD004916.pub3.
Penny A. Asbell, MD, MBA, is an OSN Cornea/External Disease Board Member. Andrew Fernandez, BA, is a fourth-year medical student at Virginia Commonwealth University School of Medicine and a clinical research coordinator at the University of Tennessee.
Literature is limited
Progressive high myopia is a serious public health concern. Parents and pediatric ophthalmologists alike are united in a desire to decrease the extent of myopia reached by children around the world. Many techniques have been explored, including environmental modifications, dilute atropine, bifocal add, orthokeratology and multifocal contact lenses.
Orthokeratology is a practice in which special lenses similar to rigid gas permeable lenses are worn overnight, achieving flattening of the cornea centrally and steepening it peripherally. This approach provides uncorrected myopia relief and 20/20 vision during the day, while also reducing peripheral hyperopic defocus. The concept of reducing peripheral defocus is a unique method of myopia prevention thought to work by slowing axial elongation. While this is an attractive approach, the safety profile of orthokeratology raises concerns about whether the risks may overshadow the benefit.
Infectious keratitis is the most significant risk of overnight contact lens wear. Specifically, due to the compressive forces necessary to flatten the cornea and offset daytime myopia as well as reduced oxygen transmission with overnight use, the corneal epithelium is more likely to suffer injury compared with routine contact lens wear. Unfortunately, unlike reports on the use of dilute atropine, many of the available reports on orthokeratology do not include the long-term follow-up necessary to definitively establish a risk profile. Furthermore, when reported, the pathogens identified in infectious keratitis associated with orthokeratology are particularly virulent and include most commonly Pseudomonas and Acanthamoeba, followed much less frequently by coagulase-negative Staphylococcus. Children afflicted required hospitalization in many reports and an average of 4.5 months of antimicrobial treatment. Most common complications of infectious keratitis include corneal scars, but corneal transplantation, cataract formation and glaucoma development did occur.
Because literature remains limited and susceptible to participation and reporting bias, we likely do not know the true relative risk of infectious keratitis in children using orthokeratology for myopia prevention. Obviously, diligent follow-up and patient education can prevent many cases of severe vision-compromising complications. Nonetheless, the availability of other techniques of myopia prevention that do not include corneal transplantation as a possible adverse outcome render orthokeratology as a less attractive treatment approach.
- Reference:
- Kam KW, et al. Infection. 2017;doi:10.1007/s15010-017-1023-2.
Courtney L. Kraus, MD, is an OSN Pediatrics/Strabismus Board Member.
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