Can orthokeratology be used to slow the progression of anisomyopia?

Paper title: Effect of orthokeratology on anisometropia control: A meta-analysis

Authors: Hou-Ren Tsai (1), Jen-Hung Wang (2), Cheng-Jen Chiu (3,4)

1. Department of Medical Administration Office, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taiwan
2. Department of Medical Research, Buddhist Tzu Chi General Hospital, Hualien, Taiwan
3. Department of Ophthalmology and Visual Science, Tzu Chi University, Hualien, Taiwan
4. Department of Ophthalmology, Haulien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taiwan

Date: December 2021

Reference:  Tsai HR, Wang JH, Chiu CJ. Effect of orthokeratology on anisometropia control: A meta-analysis. J Formos Med Assoc. 2021 Dec;120(12):2120-2127. [Link to open access paper]

This quantitative meta-analysis investigated the effectiveness of orthokeratology in controlling the progression of anisomyopia in predominantly Asian children. 10 cohort studies were included, with some examining unilateral myopic children and others bilateral anisomyopic children. The unilateral myopic group showed a mean axial length (AL) elongation difference between myopic and emmetropic eyes of 0.27 mm (p<0.01) at 1-year follow-up and 0.17 mm (p=0.03) at 2-year follow-up. The AL of the emmetropic eye increased more than the myopic eye at both years of follow-up, with a reduction in total anisometropia. In the bilateral anisomyopic group, mean AL elongation difference between high and low myopic eyes was 0.06 mm (p<0.01) at 1-year and 0.13 mm (p<0.01) at 2-year follow-up. This indicates that total anisomyopia decreased over the 2 years of follow-up; however the effect was reduced at year 2 in comparison to year 1. Few serious side effects were noted during the 2-year period. Overall, this study demonstrates that orthokeratology can effectively retard myopia progression in anisomyopia and reduce overall axial anisometropia. Consequently, eye care practitioners that are managing patients with anisomyopia should consider orthokeratology as a means of myopia control and reducing inter-eye AL difference.

If you are managing a progressing anisomyopic patient (unilaterally myopia or bilateral anisomyopic), consider fitting orthokeratology to control their progression and reduce inter-eye axial length difference. This is the only intervention for which there is evidence for anisomyopia control. 

This analysis included 7 studies of one year duration, and 3 studies of two years' duration, and nine out of the ten studies were retrospective. Additional longer term, prospective study data would be helpful to confirm this effect.  

Title: Effect of orthokeratology on anisometropia control: A meta-analysis

Authors: Hou-Ren Tsai, Jen-Hung Wang, Cheng-Jen Chiu

Background: The effectiveness of orthokeratology in retarding anisometropic progression has been investigated in several small-sample studies. This quantitative analysis aimed to elucidate the efficacy of orthokeratology for anisometropia control.

Methods: We searched PubMed, Embase, and Cochrane databases for relevant studies through September 2020. Axial length (AL) data at baseline and final follow-up were extracted, and AL elongation and difference were calculated. Methodological quality was evaluated using the risk of bias in non-randomized studies of interventions (ROBINS-I) tool. Meta-analyses were performed using a fixed-effect model based on the heterogeneity.

Results: A total of 10 cohort studies (nine retrospective studies; one prospective study) were included. The pooled results for the unilateral myopia group showed that the mean AL elongation difference between myopic and emmetropic eyes was −0.27 mm (95% CI, −0.31 to −0.22; p < 0.01) at the one-year follow-up (four studies) and −0.17 mm (95% CI, −0.33 to −0.02; p = 0.03) at the two-year follow-up (two studies). In the bilateral anisomyopic group, mean AL elongation difference between high and low myopic eyes was −0.06 mm (95% CI, −0.09 to −0.04; p < 0.01) at the one-year follow-up (seven studies) and −0.13 mm (95% CI, −0.21 to −0.06; p < 0.01) at the two-year followup (three studies).

Conclusions: This study demonstrated that orthokeratology can effectively retard myopic progression and reduce anisomyopic values. However, additional well structured randomized controlled trials or prospective studies with longer follow-up periods are warranted to address this topic in more detail.