Clinical Nomogram for Determining Expected Choroidal Thickness in Children With Myopia

Objective: A thin choroid is a recognized risk factor for myopia-associated complications and visual impairment in later life. This study aims to develop a clinical tool to identify individuals whose choroidal thickness varies from that expected for their age, sex and refraction, and who might therefore be at higher or lower risk of future myopic complications. Design: Post-hoc patient-level meta-analysis Subjects: Participants aged 6-30 years from four clinical studies: Myopia Outcome Study of Myopia in Children (MOSAIC), Treatment Optimization of Atropine Study (TOAST), Western Australia Atropine for the Treatment of Myopia study (WAATOM), Kidskin-Young Adult Myopia Study. Methods: Spherical equivalent refraction (SER) was measured by cycloplegic autorefraction and axial length (AXL) by partial coherence interferometry. Choroidal thickness (ChT) was measured by Swept Source-OCT (Triton Plus, Topcon) or Spectral Domain-OCT (Spectralis, Heidelberg). Multiple linear regression and Machine Learning approaches were applied to create prediction models for ChT as a function of age, sex, SER and AXL. Main Outcome Measures: Deviation of subfoveal ChT from the expected value a function of age, sex, SER and AXL. Results: Ordinary least square (OLS) regression with restricted cubic splines and a linear mixed model with non-linear spline terms for age and AXL both estimated ChT well, explaining over 44% of the variance. Of the remaining variance, approximately 50% was due to inter-individual differences in ChT (likely reflecting genetic, environmental or lifestyle factors), with 44% of participants having a ChT that was >50 µm thicker or thinner than expected. A clinical nomogram was generated from the OLS model to facilitate comparison of the observed ChT with that expected on the basis of SER, AXL and demographic factors. Conclusions: ChT is a known myopia biomarker that is not fully utilised to inform clinical practice. The resultant clinical ChT nomogram is a simple, visual clinical tool that provides an objective method to gauge and potentially track a myopic child's risk of myopia-related complications, such as myopic maculopathy, based on the mismatch between their measured and expected choroidal thickness.