Measurement of Choroidal Thickness in Normal Eyes Using 3D OCT-1000 Spectral Domain Optical Coherence Tomography

The choroid is the connective tissue-containing vascular layer between the retina and the sclera that provides oxygen and nourishment to the outer retina. It is associated with the pathophysiology of many diseases affecting the retina, such as age-related macular degeneration, polypoidal choroidal vasculopathy, central serous chorioretinopathy, and high myopia-related chorioretinal atrophies [1]. Because choroidal change has a major role in the development and progression of these diseases, choroidal thickness, which reflects choroidal change, provides useful information to clinicians. Adequate measurement of choroidal thickness using spectral domain optical coherence tomography (SD-OCT) is possible by introduction of an enhanced depth imaging technique and by averaging several B-scan signals from the same position [2,3]. Using a long-wavelength light source is another approach to visualize the posterior choroid and sclera [1,4]. Recent studies in a healthy population report a range of choroidal thickness from 270 to 350 µm. A negative correlation between choroidal thickness and age was previously reported [1-3,5]. Choroidal thinning is prominent in highly myopic eyes, and refractive error affects choroidal thickness [6]. Previous studies of normal choroidal thickness profiles utilized Heidelberg Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany), Cirrus HD-OCT (Carl Zeiss Meditec Inc., Dublin, CA, USA), or high-penetration OCT with long-wavelength (prototype). Moreover, normal choroidal thickness was usually reported in Western populations [2-5]. 3D OCT-1000 (Topcon, Tokyo, Japan) is another commercially available SD-OCT that supports 'choroid mode' optimized for choroidal and scleral imaging. However, the choroidal visualization ability of 3D OCT-1000 has not been reported. We therefore investigated the choroidal thickness profile based on location using 3D OCT-1000 in healthy Korean individuals and its correlations with age and refractive error.