Dynamic changes of choroidal vasculature and its association with myopia control efficacy in children during 1-year orthokeratology treatment.

Purpose: To investigate the dynamic changes of choroidal vasculature and its association in mediating ocular elongation over 1 year of orthokeratology (ortho-k) treatment.

Methods: This observational study included 8-14 year old myopic children who were willing to receive ortho-k treatment or wear single vision spectacle lenses (SVL). Axial length (AL) and choroidal characteristics, including submacular luminal area (LA), stromal area (SA), total choroidal area (TCA), choroidal vascularity index (CVI), subfoveal choroidal thickness (SFCT) and choriocapillaris flow deficits (CcFD) from OCT/OCTA images, were evaluated at baseline, 3, 6 and 12 months.

Results: After 1 year, AL elongation was significantly less in 25 children treated with ortho-k than in 29 children wearing SVL (0.17 ± 0.14 v.s. 0.28 ± 0.16 mm, P<0.01). In the ortho-k group, LA, SA, TCA and SFCT were significantly increased by 0.033 ± 0.059 mm², 0.024 ± 0.035 mm², 0.058 ± 0.087 mm², 8.9 ± 17.4 μm, respectively, at 3 months (all P<0.05). These parameters returned to near baseline levels over the following 9 months. Meanwhile, CcFD decreased by 0.83 ± 1.09 % over 12 months, but CVI remained steady during this period. No significant changes in these choroidal parameters (except for CcFD, decreased by -0.56 ± 1.23 %) were observed in the SVL group over 12 months. Increases in SFCT, LA, SA and TCA over 12 months were significantly greater in the ortho-k group than in the SVL group. Mediation analyses showed that 44.8 % of effect on inhibiting AL elongation through ortho-k was mediated via TCA (in particular LA).

Conclusions: The decelerated ocular elongation during ortho-k treatment is accompanied by increases in content of choroidal vascular lumen and stromal component. Dynamic changes of choroidal vasculature provide a possible mechanism underlying myopia control efficacy via ortho-k.