Choroidal thickness and high myopia: a cross-sectional study and meta-analysis

BACKGROUND The purpose of this study was to examine the choroidal thickness of patients with high myopia using enhanced depth imaging optical coherence tomography (EDI-OCT) and compare them with healthy subjects. METHODS We first conducted a cross-sectional study and then performed a meta-analysis to address this issue further. Using enhanced depth imaging optical coherence tomography (EDI-OCT), the macular choroidal thickness of high myopic eyes and normal control eyes were measured and compared at each location. Univariate and multivariate linear regression analyses were performed to assess the association between choroidal thickness and clinical factors such as axial length (AL), spherical equivalent (SE), and central corneal thickness. In the high myopic eyes, subgroup analysis of macular choroidal thickness was performed in eyes with or without lacquer cracks and choroidal neovascularization (CNV). The meta-analyses were conducted using the Stata software package. RESULTS The high myopic eyes had a thinner choroid than the control eyes at all macular locations (all P < 0.001). Multivariable linear regression analysis showed that the subfoveal choroidal thickness (SFCT) was not significantly thinner in association with the diagnosis. Subgroup analysis showed that the high myopia with CNV and with lacquer cracks had a significantly thinner choroid than without CNV or lacquer crack eyes. The result of our cross-sectional study is consistent with the results of the further meta-analysis with the pooled weighted mean difference (WMD) of -116.30 μm (95 % CI: -145.68, -86.92) for SFCT. CONCLUSIONS The present study, along with the comprehensive meta-analysis, indicated that in the Chinese population, the choroidal thickness in high myopic eyes was thinner than that of normal control eyes, even across different subgroups. This might be secondary to the longer AL but it is not an independent factor. The presence of CNV and of lacquer cracks is associated strongly with eyes with thinner macular choroids.