Patterns and Determinants of Choroidal Thickness in a Multiethnic Asian Population: The Singapore Epidemiology of Eye Diseases Study.

PURPOSE To describe the distribution and determinants of choroidal thickness (CT) in participants in a population study based on spectral-domain optical coherence tomography (SD-OCT) measurements. DESIGN Population-based, cross-sectional study. SUBJECTS Ethnic Chinese, Indian, and Malay adults older than 50 years without any retinal diseases (e.g., diabetic retinopathy, macular edema, age-related macular degeneration, central serous chorioretinopathy, etc.) that might affect the CT were recruited from the Singapore Epidemiology of Eye Diseases Study. METHODS Choroidal imaging was performed by SD-OCT (Spectralis, Heidelberg Engineering, Germany) in enhanced-depth imaging (EDI) mode. Subfoveal choroidal thickness (SFCT) was measured on the foveal line scan by two retinal experts independently (YS and KT) and the average used in the analyses. In Chinese and Indian cohorts in whom macular raster scans were captured, the manufacturer supplied research software (Heyex SP-X version 6.4.8.116; Heidelberg Engineering) was used to obtain automated segmentation yielding mean choroidal thickness in each of the 9 ETDRS grid sectors. MAIN OUTCOME MEASURES SFCT and regional CT in the 9 ETDRS grid sectors. RESULTS For the SFCT analysis 2,794 eyes from 1,619 participants (Chinese, Indian and Malay ) were included. The mean age was 60.9 years (SD 7.7), and 797 (49.2%) were male. Mean SFCT was 255.2 μm (SD 102.6). The normal range of SFCT was 106 to 447 μm (corresponding to 5th and 95th percentile limit of SFCT, respectively). In multivariable models, thinner SFCT was associated with older age, female, longer axial length, and Malay (vs Chinese) ethnicity. In the subset of Chinese and Indian eyes (n=1,842) in whom regional variation was evaluated the choroid was thickest at the superior and temporal sectors and thinner at inferior and nasal sectors. CONCLUSIONS SFCT is influenced by age, gender and ethnicity along with regional differences even within individual eyes. SFCT also shows a wide range in physiological limits. These data may be used as a reference in future studies.