Evaluation of Normal Choroidal Thickness in Rasht Using SD-OCT EDI Imaging

Purpose: To measure choroidal thickness in normal subjects, using optical coherent tomography (OCT) in Rasht. Methods: Normal subjects older than 20 years, living in Rasht, were selected through systematic random sampling by using the city telephone directory. The subjects underwent comprehensive eye examinations for inclusion in the study. Then, choroidal thickness was measured in both eyes by two experienced operators, using HRA2 SD-OCT EDI (software version 5.4). Choroidal thickness was measured from the line under the retinal pigmented epithelium corresponding to Bruch’s membrane to inner surface of the sclera at a horizontal line. The measurement was first made under the fovea and then at 500-µm intervals up to 3 mm on both temporal and nasal sides. The collected data were entered into the computer and SPSS statistical software version 21 was used for statistical analysis. The paired-samples t test was used to evaluate the differences in choroidal thickness in different regions. Pearson correlation test was used to determine the correlation of choroidal thickness with age. The level of significance was set at 0.05. Results: In total, 75% of the selected women were female and 25% were male with the age range of 20 to 70 years. The mean central choroidal thickness was 290.5 ± 81.5 µm for the right eye and 296.4 ± 70.5 µm for the left eye with the age range of 48.5 ± 12. The 95% confidence interval for mean choroidal thickness for the study population (Rasht) was estimated to be 275 to 306 µm. The choroid was thickest under the fovea and decreased in thickness temporally and nasally (3 mm), with more decreases at nasal region (P<0.001). There was no significant difference in choroidal thickness at various locations between the left and right eyes. Nor was there a significant difference in choroidal thickness at various locations between male and female subjects. A negative significant correlation was found between choroidal thickness and age (P<0.05) with choroidal thickness decreasing by about 2 µm for every 10 years. Conclusion: In this study, the mean central choroidal thickness was 290.45 ± 81.5 µm. The mean choroidal thickness for the population, i.e., Rasht, was 275 to 306 µm with 95% confidence interval.