Short and longer-term variations in choroidal thickness and axial length

Purpose: To examine the short (diurnal) and longer-term (12 months) changes in subfoveal choroidal thickness (SFCT) and axial length (AxL) of young adults, in order to explore the association of choroidal thickness changes with axial length. Methods: A series of baseline SFCT and AxL measurements were collected every 3 hours from 9 am to 9 pm (i.e. 5 measurements per day) on 34 young adults. Participants then returned for a single measurement of SFCT and AxL 12 months later. Results: At baseline, significant diurnal variations were observed in SFCT (p<0.001), with the trough and the peak occurring in the afternoon (mean time15:07 PM) and evening (20:50 PM), respectively. AxL also exhibited significant diurnal variations (p<0.001) and a significant negative association was observed between the diurnal SFCT and AxL changes (β = -0.338, r = -0.603, p<0.001). A significant negative association was observed between the 12 month longitudinal changes in SFCT and AxL (β = -0.25, r = -0.352, p