Wide-field choroidal thickness in myopes and emmetropes

There is a paucity of knowledge regarding the normal in-vivo thickness of the choroid beyond the macula (similar to 17 degrees). In this study, the choroidal thickness of 27 healthy young adults was examined across the macular (the central 5 mm including the fovea, parafovea, and perifovea) and extra-macular (a 5-14 mm annulus including the near-periphery and periphery) regions using wide-field optical coherence tomography, and compared between emmetropes (n = 14) and myopes (n = 13). The choroid progressively thinned beyond the parafovea (350 +/- 86 mu m) towards the periphery (264 +/- 44 mu m), and was thickest superiorly (355 +/- 76 mu m) and thinnest nasally (290 +/- 79 mu m). Choroidal thickness also varied with refractive error; myopes exhibited a thinner choroid than emmetropes in the macular region (311 +/- 88 vs. 383 +/- 66 mu m), however, this difference diminished towards the periphery (251 +/- 48 vs. 277 +/- 37 mu m). Meridional variations in choroidal thickness were not different between myopes and emmetropes. In conclusion, the choroid was thickest within the perifovea; thinned substantially towards the periphery, and exhibited the minimum and maximum peripheral thinning superiorly and nasally across a 55 degrees region respectively. Choroidal thinning associated with myopia was more pronounced in the macular than extra-macular regions.