Orthokeratology has been well established as an effective way to not only temporarily correct myopia without the need for daytime contact lenses or glasses, but also control myopia progression. It is arguably the intervention with the most research evidence for myopia control, with multiple studies indicating a consistent effect in slowing axial elongation by around 0.26mm - representing about 50% less growth - over two years.1
We know orthokeratology (OK) works consistently well for myopia control - including for toric corrections up to 3.50DC2 and for partial correction in myopes over 6D.3 The newest research in orthokeratology has investigated compliance, safety, comfort and combination treatment with atropine. Here, we'll bring you the latest knowledge with implications for clinical practice.
Orthokeratology and compliance
In Taiwan, 253 parents of children wearing OK were surveyed on wear, care and follow-up visit behaviours. Over 70% of parents had a university education and almost 90% were myopes themselves, of a mean -5.0D.
Around than half of the children had worn OK for less than a year, with the remainder having at least a year of wear. All children were aged between 6 and 13 years, with average myopia of -2.40D and up to -7.50D.
There were two interesting aspects to the findings. Firstly, parents were given a true-or-false quiz on their understanding of myopia and OK lenses and most showed strong knowledge of reasons for follow up, wearing patterns and handling. When then quizzed on compliance, parents reported the highest compliance rates for getting at least 6 hours of sleep, using the proper cleaning liquid, replacing the lens storage case and accessories every three months, and proper cleaning procedure, which were undertaken correctly in at least 80%. Lowest compliance rates were for "intensive care for lenses (removing lens protein deposition)" and "Follow-up visit" which the authors had defined as being required every 3 months. The authors also noted that 36% of the OK wearers did not have back up spectacles.
What this means for your practice: parental education is crucial, as rightfully concluded by the authors. This parent group were highly educated, myopes themselves, and engaged in their child's OK lens wear as evidenced in their recruitment to the study through a closed Facebook peer support group. Overall, their knowledge and practices were broadly appropriate, but not all parents may be so informed - reinforcing care and handling procedures for both parents and children at each follow up visit is important to ensure best possible vision and eye health outcomes in OK-wearing children.
Chang LC, Sun CC, Liao LL. Compliance with orthokeratology care among parents of young children in Taiwan. Contact Lens Anterior Eye 2021 Feb 20:101427. (link)
Orthokeratology and safety
Previous research has indicated that the risk of microbial keratitis (MK) in children wearing OK is around 13.9 per 10,000 patient years of wear, utilizing data from 677 children representing 1435 patient-years of wear. Two corneal infiltrative events were classified as MK. Almost 200 eye care practitioners in the United States were surveyed in that study, with the clinical care having occurred between 2004 and 2006.4
A new paper indicates that the risk may be lower than that. This time, data was surveyed from a group ophthalmology and optometry practice and a local Children's Hospital in Moscow, Russia. With over 23,000 OK fits between 2010 and 2018, and a sample of just over 1,000 records surveyed, the incidence of MK was estimated to be between 4.9 and 5.3 per 10,000 patient years of wear.
The improved safety profile in this recent study likely reflects the effect of gathering data from a single group of practices with standardised training, whereas the previous study obtained data from numerous different practices. It could also reflect a concerted effort to improve OK safety and compliance in the past decade or so.
What this means for your practice: OK is perhaps safer than originally indicated, at least in the setting of an experienced group practice. The risk of MK appears similar to rates associated with use of daily wear soft contact lenses, which should give eye care practitioners and parents confidence in fitting OK to children.
Bullimore MA, Mirsayafov DS, Khurai AR, Kononov LB, Asatrian SP, Shmakov AN, Richdale K, Gorev VV. Pediatric Microbial Keratitis With Overnight Orthokeratology in Russia. Eye Contact Lens. 2021 Jul 1;47(7):420-425. (link)
In other safety research, a case series was examined of all contact lens wearers under 18 years of age who presented to the University of Illinois at Chicago (UIC) Cornea Service, USA, between 2003 and 2016 and were diagnosed with Acanthamoeba keratitis (AK). The analysis found 47 cases across the 13 year review period, with a mean age of 15 (range 12-17) years. Of these 47 cases, 6 were OK wearers (13%) and 39 (83%) were soft contact lenses. None had worn non-OK RGP lenses and two cases had an unknown lens type. In these 6 cases of AK in OK wear, 1 reported using an appropriate cleaning solution, with 1 admitting to using 'city water' and 4 being unknown.
The authors concluded from this case series that even if the frequency is low, finding that 13% of AK cases were associated with OK wear was not in alignment with the 1% market penetration of OK, hence likely representing an increased risk of AK in OK wear compared with other modalities.
What this means for your practice: OK likely carries an increased risk of AK compared to soft contact lens wear. Given that water exposure to the lenses and poor cleaning regimes are key risk factors for AK, these findings highlight the importance of reinforcing correct lens care regimes in young patients at every stage of their wearing journey.
Scanzera AC, Tu EY, Joslin CE. Acanthamoeba Keratitis in Minors With Orthokeratology (OK) Lens Use: A Case Series. Eye Contact Lens. 2021 Feb 1;47(2):71-73. (link)
Orthokeratology to improve contact lens comfort
This study aimed to compare soft contact lens comfort with that of OK by refitting symptomatic soft contact lens (CL) wearers in to orthokeratology, and measuring any improvement in ocular symptoms and signs. All wearers were aged 18-45 years and completed comfort questionnaires at baseline, as soft CL wearers, and again after three months of OK wear. Whilst 40 soft CL wearers were refit into OK, 5 didn't continue due to OK-associated discomfort.
In those who completed 3 months of OK wear, their acuity was equivalent in OK as it had been in soft CLs. Clinical signs of dry eye were evaluated through blepharitis grading, noninvasive tear break-up time (NIBUT), tear meniscus height (TMH), phenol red thread (PRT), and conjunctival staining. With almost 50% meeting the dry eye signs diagnostic criteria as soft CL wearers, this reduced to 26% after one month in OK.
The most dramatic improvements were in the surveyed comfort scores. The Standardized Patient Evaluation of Eye Dryness (SPEED) questionnaire results reduced from an average of 12.03+4.03 at baseline (where a score over 9.9 indicates severe dry eye symptoms) to an average of 3.66+4.82 indicating an improvement to mild or absent symptoms. This improvement was significant after only one month of OK wear.
What this means for your practice: pre-presbyopic adult patients with symptomatic dry eye in soft CL wear are likely to feel more comfortable when refit into OK wear. Although not all may be able to be successfully refit, the symptomatic improvement can be noticeable after only one month of OK wear.
Duong K, McGwin G Jr, Franklin QX, Cox J, Pucker AD. Treating Uncomfortable Contact Lens Wear With Orthokeratology. Eye Contact Lens. 2021 Feb 1;47(2):74-80. (link)
Combining orthokeratology with atropine
A new meta-analysis of low-concentration atropine combined with OK showed a mean 0.25mm axial elongation in a year, compared to 0.35mm in OK alone, giving a mean difference of 0.09mm additional efficacy provided by the combination. The study involved data from 341 participants in 5 studies, from one month to two years in duration. The greatest effect was noted in the first six months of combined treatment and a variety of atropine concentrations were used: 0.01%, 0.025% and even 0.125%. Interestingly, the 0.125% dataset showed the least efficacy, although the meta-analysis was unable to isolate which concentration could be most effective, and did not provide any data on impact of age or baseline refraction on the combined efficacy.
Gao C, Wan S, Zhang Y, Han J. The Efficacy of Atropine Combined With Orthokeratology in Slowing Axial Elongation of Myopia Children: A Meta-Analysis. Eye Contact Lens. 2021 Feb 1;47(2):98-103. (link)
A one-year study of Chinese children aged 6-11 years with myopia of 1-4D found axial elongation of 0.07mm in the atropine-and-OK (AOK) group and 0.16mm in the OK monotherapy group, again reflecting an increased efficacy of 0.09mm over one year. The difference was measured in the first six months, with no significant difference in axial growth between the groups from six to twelve months. There was no comment made on whether the effect was increased in children based on their age or baseline refractive error. Pupil size increased 0.36mm in bright light (photopic) measurement in the AOK children, and there was a relationship found between larger pupils and less axial growth, although pupil size only explained 18% of the variation.
Tan Q, Ng AL, Choy BN, Cheng GP, Woo VC, Cho P. One-year results of 0.01% atropine with orthokeratology (AOK) study: a randomised clinical trial. Ophthalmic Physiol Opt. 2020 Sep;40(5):557-566. (link)
The longest clinical study of 0.01% atropine combined with OK involved 80 Japanese children aged 8-12 years with myopia of 1-6D. Interestingly, the combination showed a significant effect only for 1-3D myopes and not for 3-6D myopes. This appeared to be the case because the moderate (3-6D) myopes were progressing more slowly than the low (1-3D) myopes. In these low myopes, axial length increased 0.30mm in the combined treatment group compared to 0.48mm in the OK-only group, representing a 0.18mm improved efficacy over two years. There was no correlation between younger age and increased efficacy with the combined treatment.
Kinoshita N, Konno Y, Hamada N. et al. Efficacy of combined orthokeratology and 0.01% atropine solution for slowing axial elongation in children with myopia: a 2-year randomised trial. Sci Rep 2020;10:12750. (link)
What this means for your practice: OK wear combined with atropine is likely to increase myopia control efficacy, with the effect most pronounced in the first six months. Whilst current research indicates that higher concentrations than 0.01% are needed for effective atropine monotherapy, 0.01% has been most commonly researched in combination with OK and appears to be effective. Perhaps it is best targeted to low myopes of 1-3D, although this needs to be confirmed with further research. There is a small relationship between increased pupil size in combined treatment and a better myopia control effect.
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- Sun Y, Xu F, Zhang T, Liu M, Wang D, Chen Y, Liu Q. Orthokeratology to control myopia progression: a meta-analysis. PLoS One. 2015 Apr 9;10(4):e0124535. (link)
- Chen C, Cheung SW, Cho P. Myopia control using toric orthokeratology (TO-SEE study). Investigative ophthalmology & visual science. 2013 Oct 1;54(10):6510-7. (link)
- Charm J, Cho P. High myopia-partial reduction ortho-k: a 2-year randomized study. Optom Vis Sci. 2013 Jun;90(6):530-9. (link)
- Bullimore MA, Sinnott LT, Jones-Jordan LA. The risk of microbial keratitis with overnight corneal reshaping lenses. Optom Vis Sci 2013;90:937-944. (link)