There is still some disagreement about the results and corresponding interpretation of SFCT in many circumstances. SFCT was found to be negatively correlated with age, and the SFCT in males was 18% higher than in females in some investigations17, 18. However, a different study demonstrated no significant correlation between SFCT and age and sex, nor was there a significant correlation with ethnicity19. Since EDI-OCT is a new technique and increasing attention has been paid to choroidal thickness, the accurate determination of the boarder of the choroid is crucial. Accurate determination of SFCT is composed of two aspects: one is the outer boarder of the RPE, which is always clear and easy to define, and the other is the outer boarder of the choroid, which is not so clear and is easy to be confused by factors such as the linear artifact.