Early choroidal thickness changes predict myopia control response to peripheral defocus spectacles in premyopic children

PURPOSE: To investigate whether early changes in choroidal thickness predict long-term treatment response to peripheral defocus spectacles in premyopic children with insufficient hyperopic reserve. METHODS: Two hundred children aged 6-8 years with cycloplegic spherical equivalent refraction +0.25 to +0.75 diopters (D) and annual hyperopic reserve depletion ≥0.75D were randomized 1:1 to peripheral defocus spectacles with plano central-zone (PDS group, n = 100) or plano-single vision spectacles (SVS group, n = 100). Primary outcome was the subfoveal choroidal thickness (SFCT) change at 12 months measured by swept-source optical coherence tomography. Secondary outcomes included axial length (AL), cycloplegic spherical equivalent refraction, and myopia incidence. The predictive value of 3-month SFCT changes for 12-month AL outcomes within the PDS group was assessed using receiver operating characteristic analysis. RESULTS: At 12 months, mean SFCT increased by 8.34 ± 18.67 μm in the PDS group, whereas it decreased by 16.82 ± 21.43 μm in the SVS group (mean difference: 25.16 μm; 95% CI: 19.84-30.48; p < 0.001). Mean AL elongation was 0.19 ± 0.14 mm (PDS) versus 0.32 ± 0.16 mm (SVS), representing 41% control efficacy (mean difference: -0.13 mm; 95% CI: -0.17 to -0.09; p < 0.001). Myopia incidence (spherical equivalent refraction ≤-0.50D) was 18% (PDS) versus 44% (SVS; p < 0.001). Within the PDS group, SFCT changes at 3 months predicted 12-month treatment response (AL elongation <0.25 mm) with area under curve 0.76 (95% CI: 0.69-0.84; p < 0.001). Children with early SFCT thickening (≥+5 μm at 3 months) showed superior 12-month AL control (0.16 ± 0.11 mm) compared to those with thinning (<-5 μm; 0.28 ± 0.15 mm; p < 0.001). No serious adverse events occurred. CONCLUSIONS: Peripheral defocus spectacles significantly controlled axial elongation and reduced myopia incidence in premyopic children with insufficient hyperopic reserve. Three-month choroidal thickness changes represent a valid early predictive biomarker for treatment response, enabling personalized intervention by 3 months rather than waiting 12 months for conventional outcomes. Early choroidal thickening identifies optimal responders, supporting choroidal perfusion mechanisms in myopia control.