Background: The purpose of this study was to examine the choroidal thickness (CT) of patients with high myopia using enhanced depth imaging optical coherence tomography(EDI-OCT) and compare with healthy subjects.

Methods: A case-control study of 107 eyes (57patients) with high myopia and 60 eyes (30 patients) of emmetropes. Choroidal imaging was performed using enhanced depth imaging spectral domain optical coherence tomography. CT was measured at, subfovea, 1mm and 3mm nasal and temporal to fovea.

Results: Statistical analysis was performed to evaluate CT at different locations and to correlate CT with axial length(AL) and spherical equivalent(SE).Mean SE was -12.07+-3.184D in eyes with high myopia and 25.66+-8.39D in normal control group. Mean AL was 26.68+-1.577mm in eyes with high myopia and 22.88+-0.56mm in normal control group. The CT at the subfovea was significantly thinner (mean+- standard error: 192.79+-51.61µm) for high myopic eyes compared to emmetropes (305.30+-60.11µm, p<0.001).Likewise, CT in high myopic group was significantly thinner than emmetropic control group at all locations (p for trend <0.001 for all locations).Choroid was thinnest at nasal 3mm location in both the myopic (136.46+-50.33µm) and emmetropic (289.02+-60.15 µm) groups. Choroid was thickest subfoveally in both the myopic (192.79+-51.61 µm) and emmetropic (305.30+-60.11µm) groups. CT was negatively correlated with SE and AL.

Conclusions: High myopic eyes have significantly thinner choroid compared to emmetropic eyes. Axial length and spherical equivalent are significant predictors of choroidal thickness.

Keywords: Myopia, OCT, Choroidal thickness.

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Dr Nazia Anjum