ORTHOKERATOLOGY (ortho-k) has arguably the longest history of effectively slowing myopia progression in children and teenagers and the widest evidence base for a range of refractive conditions concurrent with myopia. It was 20 years ago that the first clinical trial of ortho-k for myopia control was published, a pilot study using a historical (not concurrent) control group wearing single-vision spectacles. Axial elongation and vitreous chamber depth were both slowed by around 50% over 2 years (0.25 mm in absolute terms for both measures) (Cho et al, 2005).
Since then, an impressive volume of research has confirmed ortho-k’s robust efficacy for slowing the progression of low-to-moderate myopia, and in children aged 6 to 16 years at commencement of wear (Sun et al, 2015). The strongest protection from fast progression is in those aged 6 to 8 years, where the number needed to treat (NNT) of 1.8 indicates that treating just 2 younger children who have ortho-k would prevent 1 of them experiencing rapid progression exceeding 0.36 mm/year (Cho and Cheung, 2017).
Ortho-k’s gold stars for myopia treatment don’t stop there. It is the only intervention that appears to slow myopia progression in the presence of moderate to high astigmatism (1.25 DC to 3.50 DC), due to its capacity for toric fitting and correction (Chen et al, 2013). In high myopes (over 6 D), ortho-k partial treatment to 4 D—with the residual myopia corrected by single-vision spectacles—appears to be just as effective in slowing myopia progression as full monotherapy correction in lower myopes (Charm and Cho, 2013).
Anisometropia? No problem for ortho-k! In both monocular myopia and bilateral anisomyopia with intereye differences exceeding 1 D, ortho-k can reduce growth of the larger eye in relation to the less myopic eye (Tsai et al, 2021).
The first treatment to show an efficacy “boost” in combination with atropine 0.01% (Tsai et al, 2022), ortho-k has since exhibited the propensity for “boosted” efficacy with alteration of treatment zone size (Guo et al, 2023). Both of these “boost” effects appear to be significant only in the first 6 months, perhaps indicating an adaptation effect and a potential path to further research on optimizing treatment outcomes.
The quality-of-life benefits for children and teens wearing ortho-k also must be noted. Compared to wearing single-vision spectacles, kids rate their overall vision, far vision, appearance, satisfaction, handling, effect on activities, and peer perceptions as better with ortho-k (Santodomingo-Rubido et al, 2013; Yang et al, 2021). Only near vision was rated the same (Santodomingo-Rubido et al, 2013) or better (Yang et al, 2021) in spectacles.
The safety profile of ortho-k in kids appears to be high, with the newest data indicating that overnight ortho-k wear in children may have a lower risk than overnight wear of soft contact lenses (the latter measured primarily in adults) (Bullimore et al, 2021; Stapleton et al, 2008), with a rate of microbial keratitis of around 5 per 10,000 patient wearing years in pediatric ortho-k (Bullimore et al, 2021).
Nearly 2 decades ago, ortho-k and atropine 1% (Chua et al, 2006) were the only evidence-based options for myopia management. Now, a plethora of spectacle and soft contact lens designs, and lower (and more palatable for patients) concentrations of atropine are available. All have robust levels of evidence, and most appear to be similar in efficacy to ortho-k (Sankaridurg et al, 2023).
There’s no doubt that the options available to the myopia management practices of today allow practitioners to tailor the treatment to the individual patient’s lifestyle needs and ocular parameters. While these choices and newer developments make the myopia field an exciting place to be: the “wow factor” for patients, the practice-building loyalty, and the robust evidence base of ortho-k means it holds a special place in
my heart.
References
1. Cho P, Cheung SW, Edwards M. The longitudinal orthokeratology research in children (LORIC) in Hong Kong: a pilot study on refractive changes and myopic control. Curr Eye Res. 2005;30(1):71-80. doi: 10.1080/02713680590907256
2. Sun Y, Xu F, Zhang T, et al. Orthokeratology to control myopia progression: a meta-analysis. PLoS One. 2015;10(4):e0124535. doi: 10.1371/journal.pone.0124535
3. Cho P, Cheung SW. Protective role of orthokeratology in reducing risk of rapid axial elongation: a reanalysis of data from the ROMIO and TO-SEE studies. Invest Ophthalmol Vis Sci. 2017;58(3):1411-1416. doi: 10.1167/iovs.16-20594
4. Chen C, Cheung SW, Cho P. Myopia control using toric orthokeratology (TO-SEE study). Invest Ophthalmol Vis Sci.2013;54(10):6510-6517. doi: 10.1167/iovs.13-12527
5. Charm J, Cho P. High myopia-partial reduction ortho-k: a 2-year randomized study. Optom Vis Sci. 2013;90(6):530-539. doi: 10.1097/OPX.0b013e318293657d
6. Tsai HR, Wang JH, Chiu CJ. Effect of orthokeratology on anisometropia control: A meta-analysis. J Formos Med Assoc. 2021;120(12):2120-2127. doi: 10.1016/j.jfma.2021.05.024
7. Tsai HR, Wang JH, Huang HK, Chen TL, Chen PW, Chiu CJ. Efficacy of atropine, orthokeratology, and combined atropine with orthokeratology for childhood myopia: A systematic review and network meta-analysis. J Formos Med Assoc. 2022;121(12):2490-2500. doi: 10.1016/j.jfma.2022.05.005
8. Guo B, Cheung SW, Kojima R, Cho P. Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study: a 2-year randomised clinical trial. Ophthalmic Physiol Opt. 2023;43(6):1449-1461. doi: 10.1111/opo.13208
9. Santodomingo-Rubido J, Villa-Collar C, Gilmartin B, Gutiérrez-Ortega R. Myopia control with orthokeratology contact lenses in Spain: a comparison of vision-related quality-of-life measures between orthokeratology contact lenses and single-vision spectacles. Eye Contact Lens. 2013;39(2):153-157. doi: 10.1097/ICL.0b013e31827a0241
10. Yang B, Ma X, Liu L, Cho P. Vision-related quality of life of Chinese children undergoing orthokeratology treatment compared to single vision spectacles. Cont Lens Anterior Eye. 2021;44(4):101350. doi: 10.1016/j.clae.2020.07.001
11. Bullimore MA, Mirsayafov DS, Khurai AR, et al. Pediatric microbial keratitis with overnight orthokeratology in Russia. Eye Contact Lens. 2021;47(7):420-425. doi: 10.1097/ICL.0000000000000801
12. Stapleton F, Keay L, Edwards K, et al. The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology. 2008;115(10):1655-1662. doi: 10.1016/j.ophtha.2008.04.002
13. Chua WH, Balakrishnan V, Chan YH, et al. Atropine for the treatment of childhood myopia. Ophthalmology.2006;113(12):2285-2291. doi: 10.1016/j.ophtha.2006.05.062
14. Sankaridurg P, Berntsen DA, Bullimore MA, et al. IMI 2023 Digest. Invest Ophthalmol Vis Sci. 2023;64(6):7. doi: 10.1167/iovs.64.6.7
