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. © Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.