RESUMO
Objective:To characterize the distribution characteristics of choroidal thickness in healthy normal subjects and to define the diagnostic cut-off value for pachychoroid.Methods:A cross-sectional study design was carried out.Four hundred and forty-six eyes of 230 healthy subjects from the pachychoroid disease spectrum (PCD) cohort in Beijing Tongren Hospital from April 2018 to June 2021, were enrolled for the choroidal thickness distribution analysis.Three hundred and fourteen eyes of 274 patients with PCD including 149 eyes of 113 patients with central serous chorioretinopathy, 95 eyes of 81 patients with polypoid choroidal vasculopathy, 70 eyes of 60 patients with neovascular age-related macular degeneration, along with 382 eyes of 199 normal subjects matched for refractive error, age and gender with PCD were selected for likelihood ratio analysis.Routine eye examinations including the best corrected visual acuity, intraocular pressure, slit-lamp microscopy, dilated fundus examination and color fundus photography were performed in all subjects.Swept-source optical coherence tomography (SS-OCT) of 9 mm×9 mm scanning mode was used to measure the subfoveal choroidal thickness (SFCT) automatically in nine macular regions according to the Early Treatment Diabetic Retinopathy Study classification system using TOPCON Advanced Boundary Segmentation (TABS) software.Pearson linear correlation analysis and Spearman rank correlation analysis were adopted to evaluate the correlations between SFCT and age, diopter.Multiple linear regression was employed to analyze the factors affecting SFCT.After age and refractive error adjustment, the likelihood ratio test was used to determine the diagnostic cut-off value for pachychoroid.This study adhered to the Declaration of Helsinki.The study protocol was approved by an Ethics Committee of Beijing Tongren Hospital (No.TRECKY2016-054). Written informed consent was obtained from each subject prior to entering the cohort.Results:A negative correlation was found between SFCT and age in normal eyes ( r=-0.34, P<0.001), in both normal male and female subjects ( r=-0.43, P<0.001; r=-0.38; P<0.001). A weak positive correlation was found between SFCT and diopter ( rs=0.19, P<0.001). It was found that age and diopter were strongly correlated with SFCT (both at P<0.001). The cut-off values for pachychoroid in 20-39 years group, 40-59 years group, 60-79 years group and ≥80 years group were 320-330 μm, 330-340 μm, 250-275 μm and 200-225 μm, respectively.The percentages of eyes with pachychoroid in 20-39 years group, 40-59 years group and ≥60 years group were 14.71%(10/68), 24.48%(47/192) and 28.89%(55/184), respectively, showing statistically significant differences among them ( χ2=6.170, P=0.046; LR=6.579, P=0.037). The proportion of pachychoroid in ≥60 years group was significantly higher than that of 20-39 years group, showing a statistically significant difference ( χ2=5.982, P=0.014; LR=6.479, P=0.011). Conclusions:The distribution characteristics of pachychoroid vary in normal subjects over age.Age and diopter are the independent influencing factors of SFCT.