Biomarker changes of choroidal architecture preceding myopia onset in Chinese school children: a 3-year prospective cohort study

BACKGROUND/AIMS: To characterise the temporal dynamics of choroidal changes relative to myopia onset and determine their associations with myopia onset in school children. METHODS: The 3-year prospective cohort study consisted of 180 emmetropic school-children. Cycloplegic auto-refractions were performed annually. Choroidal images acquired via swept-source optical coherence tomography until myopia onset were analysed. Choroidal architecture was characterised based on submacular choroidal thickness (ChT), choroidal vascularity index (CVI), luminal area (LA), stromal area (SA) and total choroidal area (TCA) measurements. Time to myopia onset was defined as the first annual follow-up visit with spherical equivalent ≤-0.50 dioptres. RESULTS: A total of 165 participants (330 eyes, 91.7%) who completed at least one annual follow-up were included. During 36 months, 168 eyes of 100 participants developed myopia. Refractive shift and axial elongation showed significant non-linear trends in which they accelerated dramatically approximately 2 years prior to myopia onset. Notably, ChT, as well as CVI, LA, SA and TCA, exhibited significant linear declines throughout the 3 years when these eyes progressed to myopia, whereas they remained unchanged in persistent non-myopic eyes. Multivariable accelerated failure time models showed that a greater decline rate of these choroidal parameters (per SD) shortened the time to myopia onset, with time ratios ranging from 1.26 to 1.76. The area under receiver-operating characteristic curves for annual choroidal changes effectively distinguished incident myopia (0.83-0.89). CONCLUSIONS: Alterations in choroidal architecture are an early indicator for the disruption of normal emmetropisation and the onset of myopia.