Optical coherence tomography angiography for the assessment of choroidal vasculature in high myopia

Aims To assess specific layers of the choroid in highly myopic young adults and to examine their associations with levels of myopia. Methods We recruited 51 young myopes (n=91 eyes) from the Singapore Cohort of Risk Factors for Myopia cohort. We performed standardised optical coherence tomography (OCT) and OCT angiography imaging and developed a novel segmentation technique assessing choroidal layers' thickness (overall choroidal thickness (CT), medium-vessel choroidal layer (MVCL) thickness, large-vessel choroidal layer (LVCL)) and vasculature (choroidal vessel density (%), choroidal branch area (CBA, %) and mean choroidal vessel width (MCVW, mm)). Results We found that eyes with extreme myopia (EM) had thinner vascular layers compared with high myopia (HM), that is, LVCL (36.0±1.5 vs 39.2±1.2 μm, p=0.002) and MVCL (185.5±5.7 vs 198.2±4.6 μm, p=0.014). Overall CT was thinnest in the nasal and inferior quadrants in EM (nasal: 157.1±9.6 vs 187.2±8.3 μm, p<0.001; superior: 236.6±11.1 vs 257.0±9.5 μm, p=0.02; temporal: 228.0±10.6 vs 254.3±8.8 μm, p=0.012; and inferior quadrant: 198.7±10.0 vs 239.8±8.3 μm, p=<0.001) when compared with HM. We also observed significantly more vessel branching in eyes with EM as compared with eyes with HM (CBA, 10.2%±0.7% vs 9.95%±0.8%, p=0.018). Conclusions The novel segmentation technique and introduced choroidal parameters may serve as new biomarkers to study disease conditions in myopia.