Prevalence of choroidal naevi in Germany: a cross-sectional analysis of the BiDirect study

BACKGROUND: Choroidal naevi (CN) are small, and mostly asymptomatic choroidal lesions. Despite their benignity, identification and follow-up of CN is required as malignant transformation is possible. CN prevalence was shown to vary greatly depending on ethnical descent, but data from European countries are rare. The aim of this study was to estimate the prevalence of CN based on fundus images from participants of the prospective German BiDirect study. METHODS: Observational cross-sectional study of participants aged 37-68 years separated into three cohorts: patients with (1) depression, (2) acute cardiovascular disease, (3) participants of the general population. Participants with at least one 45°-wide macula-centred image of both eyes were included. General health indicators and eye function were assessed. The prevalence of posteriorly localised CN was calculated. Age-standardization was performed using the European Standard Population of 2013 (ESP2013) and the U.S. 2000 Standard Population (US2000). To estimate the entire fundus prevalence of CN, we applied a correction factor of 2.5 based on the assumption that 40% of all CN were detected by the study's method. A sensitivity analysis was also performed. The association between CN presence and health indicators was investigated using logistic regression. RESULTS: 1170 participants were included. When fundus image was acquired, participants were aged 37-68 years (mean ± standard deviation: 54 ± 7.8) and 49% were females. Mean visual acuity was 0.20 ± 0.2 LogMAR on both eyes. At least one CN was detected in 36 participants. Thus, the crude prevalence of posterior CN was 3.1% (95% confidence interval: 2.1-4.1). After age-standardization, ESP2013-prevalence was 2.6% (95% CI: 2.2-3.0). A sensitivity analysis was performed to explore the potential prevalence of CN in the entire fundus; if 40% of CN were detected by our method, the entire fundus prevalence would be 7.7% (95% CI: 6.1-9.3). No association between CN and age, sex, or general health indicators was identified; the presence of CN did not impact visual acuity. CONCLUSIONS: In regions with demographics like those in the German BiDirect study, posteriorly localised CN can be expected in approximately 3.1% of the population. However, the prevalence of CN across the entire fundus remains difficult to determine.