Correlation between foveal choroidal thickness with age, refraction and axial lenght.

Purpose:to correlate foveal choroidal thickness (CT) with age, refraction and axial lenght. Methods:we examined with SD-OCT (OPKO-OTI) 84 healthy subjects ageing between 15 and 83 years with refraction between +2 and -35 Sferical Equivalent. We obtained an horizontal scan at foveal level and measured CT from RPE line to the iperreflective line behind the large vessel layer of the choroid. Axial length (IOL Master, Carl Zeiss Meditec) was also evaluated. We divided the eyes into 3 groups according to the age (GrA <40 yrs; GrB 41-64 yrs; GrC >65 yrs) and in each group CT was correlated with refraction and axial length. Results:After excluding eyes with concomitant pathologies other than high myopia, 143 eyes were evaluated. Ageing was associated with a progressive decrease in CT, from a mean of 305 µm in GrA to 190 µm in GrB and 145 µm in GrC. Increasing myopic refraction and axial length were associated with a progressive CT decrease in each group of age. CT showed a statistical difference between emmetropic eyes (±2 D, mean CT 312 µm) and those presenting simple myopia (<6 D, mean CT 243 µm). Over 16 D, mean CT was 72.5 µm (about four times thinner than in emmetropic eyes). At high levels of myopia however, axial length was more correlated with CT decrease than refractive error. Conclusions:Choroidal thickness progressively decreases according to the age, with a significant loss detectable since the age of forty. High myopia is characterized by a typical and marked choroidal thinning, more correlated to axial length than to refractive error.